Merge tag 'overflow-v4.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull overflow updates from Kees Cook:
"This adds the new overflow checking helpers and adds them to the
2-factor argument allocators. And this adds the saturating size
helpers and does a treewide replacement for the struct_size() usage.
Additionally this adds the overflow testing modules to make sure
everything works.

I'm still working on the treewide replacements for allocators with
"simple" multiplied arguments:

*alloc(a * b, ...) -> *alloc_array(a, b, ...)

and

*zalloc(a * b, ...) -> *calloc(a, b, ...)

as well as the more complex cases, but that's separable from this
portion of the series. I expect to have the rest sent before -rc1
closes; there are a lot of messy cases to clean up.

Summary:

- Introduce arithmetic overflow test helper functions (Rasmus)

- Use overflow helpers in 2-factor allocators (Kees, Rasmus)

- Introduce overflow test module (Rasmus, Kees)

- Introduce saturating size helper functions (Matthew, Kees)

- Treewide use of struct_size() for allocators (Kees)"

* tag 'overflow-v4.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
treewide: Use struct_size() for devm_kmalloc() and friends
treewide: Use struct_size() for vmalloc()-family
treewide: Use struct_size() for kmalloc()-family
device: Use overflow helpers for devm_kmalloc()
mm: Use overflow helpers in kvmalloc()
mm: Use overflow helpers in kmalloc_array*()
test_overflow: Add memory allocation overflow tests
overflow.h: Add allocation size calculation helpers
test_overflow: Report test failures
test_overflow: macrofy some more, do more tests for free
lib: add runtime test of check_*_overflow functions
compiler.h: enable builtin overflow checkers and add fallback code

crypto/af_alg.c

···
 		sg = sgl->sg;
 
 	if (!sg || sgl->cur >= MAX_SGL_ENTS) {
-		sgl = sock_kmalloc(sk, sizeof(*sgl) +
-				       sizeof(sgl->sg[0]) * (MAX_SGL_ENTS + 1),
+		sgl = sock_kmalloc(sk,
+				   struct_size(sgl, sg, (MAX_SGL_ENTS + 1)),
 				   GFP_KERNEL);
 		if (!sgl)
 			return -ENOMEM;

drivers/base/devres.c

···
 static __always_inline struct devres * alloc_dr(dr_release_t release,
 						size_t size, gfp_t gfp, int nid)
 {
-	size_t tot_size = sizeof(struct devres) + size;
+	size_t tot_size;
 	struct devres *dr;
+
+	/* We must catch any near-SIZE_MAX cases that could overflow. */
+	if (unlikely(check_add_overflow(sizeof(struct devres), size,
+					&tot_size)))
+		return NULL;
 
 	dr = kmalloc_node_track_caller(tot_size, gfp, nid);
 	if (unlikely(!dr))

drivers/clk/bcm/clk-bcm2835-aux.c

···
 	if (IS_ERR(reg))
 		return PTR_ERR(reg);
 
-	onecell = devm_kmalloc(dev, sizeof(*onecell) + sizeof(*onecell->hws) *
-			       BCM2835_AUX_CLOCK_COUNT, GFP_KERNEL);
+	onecell = devm_kmalloc(dev,
+			       struct_size(onecell, hws,
+					   BCM2835_AUX_CLOCK_COUNT),
+			       GFP_KERNEL);
 	if (!onecell)
 		return -ENOMEM;
 	onecell->num = BCM2835_AUX_CLOCK_COUNT;

drivers/clk/bcm/clk-bcm2835.c

···
 	size_t i;
 	int ret;
 
-	cprman = devm_kzalloc(dev, sizeof(*cprman) +
-			      sizeof(*cprman->onecell.hws) * asize,
+	cprman = devm_kzalloc(dev,
+			      struct_size(cprman, onecell.hws, asize),
 			      GFP_KERNEL);
 	if (!cprman)
 		return -ENOMEM;

drivers/clk/bcm/clk-iproc-asiu.c

···
 	if (WARN_ON(!asiu))
 		return;
 
-	asiu->clk_data = kzalloc(sizeof(*asiu->clk_data->hws) * num_clks +
-				 sizeof(*asiu->clk_data), GFP_KERNEL);
+	asiu->clk_data = kzalloc(struct_size(asiu->clk_data, hws, num_clks),
+				 GFP_KERNEL);
 	if (WARN_ON(!asiu->clk_data))
 		goto err_clks;
 	asiu->clk_data->num = num_clks;

drivers/clk/bcm/clk-iproc-pll.c

···
 	if (WARN_ON(!pll))
 		return;
 
-	clk_data = kzalloc(sizeof(*clk_data->hws) * num_clks +
-				sizeof(*clk_data), GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, num_clks), GFP_KERNEL);
 	if (WARN_ON(!clk_data))
 		goto err_clk_data;
 	clk_data->num = num_clks;

drivers/clk/berlin/bg2.c

···
 	u8 avpll_flags = 0;
 	int n, ret;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-			   sizeof(*clk_data->hws) * MAX_CLKS, GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, MAX_CLKS), GFP_KERNEL);
 	if (!clk_data)
 		return;
 	clk_data->num = MAX_CLKS;

drivers/clk/berlin/bg2q.c

···
 	struct clk_hw **hws;
 	int n, ret;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-			   sizeof(*clk_data->hws) * MAX_CLKS, GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, MAX_CLKS), GFP_KERNEL);
 	if (!clk_data)
 		return;
 	clk_data->num = MAX_CLKS;

drivers/clk/clk-asm9260.c

···
 	int n;
 	u32 accuracy = 0;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-			   sizeof(*clk_data->hws) * MAX_CLKS, GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, MAX_CLKS), GFP_KERNEL);
 	if (!clk_data)
 		return;
 	clk_data->num = MAX_CLKS;

drivers/clk/clk-aspeed.c

···
 	if (!scu_base)
 		return;
 
-	aspeed_clk_data = kzalloc(sizeof(*aspeed_clk_data) +
-			sizeof(*aspeed_clk_data->hws) * ASPEED_NUM_CLKS,
-			GFP_KERNEL);
+	aspeed_clk_data = kzalloc(struct_size(aspeed_clk_data, hws,
+					      ASPEED_NUM_CLKS),
+				  GFP_KERNEL);
 	if (!aspeed_clk_data)
 		return;
 

drivers/clk/clk-clps711x.c

···
 	if (!base)
 		return ERR_PTR(-ENOMEM);
 
-	clps711x_clk = kzalloc(sizeof(*clps711x_clk) +
-			sizeof(*clps711x_clk->clk_data.hws) * CLPS711X_CLK_MAX,
-			GFP_KERNEL);
+	clps711x_clk = kzalloc(struct_size(clps711x_clk, clk_data.hws,
+					   CLPS711X_CLK_MAX),
+			       GFP_KERNEL);
 	if (!clps711x_clk)
 		return ERR_PTR(-ENOMEM);
 

drivers/clk/clk-efm32gg.c

···
 	void __iomem *base;
 	struct clk_hw **hws;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-			   sizeof(*clk_data->hws) * CMU_MAX_CLKS, GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, CMU_MAX_CLKS),
+			   GFP_KERNEL);
 
 	if (!clk_data)
 		return;

drivers/clk/clk-gemini.c

···
 	int ret;
 	int i;
 
-	gemini_clk_data = kzalloc(sizeof(*gemini_clk_data) +
-			sizeof(*gemini_clk_data->hws) * GEMINI_NUM_CLKS,
-			GFP_KERNEL);
+	gemini_clk_data = kzalloc(struct_size(gemini_clk_data, hws,
+					      GEMINI_NUM_CLKS),
+				  GFP_KERNEL);
 	if (!gemini_clk_data)
 		return;
 

drivers/clk/clk-s2mps11.c

···
 	if (!s2mps11_clks)
 		return -ENOMEM;
 
-	clk_data = devm_kzalloc(&pdev->dev, sizeof(*clk_data) +
-				sizeof(*clk_data->hws) * S2MPS11_CLKS_NUM,
+	clk_data = devm_kzalloc(&pdev->dev,
+				struct_size(clk_data, hws, S2MPS11_CLKS_NUM),
 				GFP_KERNEL);
 	if (!clk_data)
 		return -ENOMEM;

drivers/clk/clk-scmi.c

···
 		return -EINVAL;
 	}
 
-	clk_data = devm_kzalloc(dev, sizeof(*clk_data) +
-				sizeof(*clk_data->hws) * count, GFP_KERNEL);
+	clk_data = devm_kzalloc(dev, struct_size(clk_data, hws, count),
+				GFP_KERNEL);
 	if (!clk_data)
 		return -ENOMEM;
 

drivers/clk/clk-stm32h7.c

···
 	const char *hse_clk, *lse_clk, *i2s_clk;
 	struct regmap *pdrm;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-			sizeof(*clk_data->hws) * STM32H7_MAX_CLKS,
-			GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, STM32H7_MAX_CLKS),
+			   GFP_KERNEL);
 	if (!clk_data)
 		return;
 

drivers/clk/clk-stm32mp1.c

···
 
 	max_binding =  data->maxbinding;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-				  sizeof(*clk_data->hws) * max_binding,
-				  GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, max_binding),
+			   GFP_KERNEL);
 	if (!clk_data)
 		return -ENOMEM;
 

drivers/clk/davinci/da8xx-cfgchip.c

···
 	struct da8xx_usb0_clk48 *usb0;
 	struct da8xx_usb1_clk48 *usb1;
 
-	clk_data = devm_kzalloc(dev, sizeof(*clk_data) + 2 *
-				sizeof(*clk_data->hws), GFP_KERNEL);
+	clk_data = devm_kzalloc(dev, struct_size(clk_data, hws, 2),
+				GFP_KERNEL);
 	if (!clk_data)
 		return -ENOMEM;
 

drivers/clk/mvebu/armada-37xx-periph.c

···
 	if (!driver_data)
 		return -ENOMEM;
 
-	driver_data->hw_data = devm_kzalloc(dev, sizeof(*driver_data->hw_data) +
-			    sizeof(*driver_data->hw_data->hws) * num_periph,
-			    GFP_KERNEL);
+	driver_data->hw_data = devm_kzalloc(dev,
+					    struct_size(driver_data->hw_data,
+							hws, num_periph),
+					    GFP_KERNEL);
 	if (!driver_data->hw_data)
 		return -ENOMEM;
 	driver_data->hw_data->num = num_periph;

drivers/clk/mvebu/armada-37xx-tbg.c

···
 	void __iomem *reg;
 	int i, ret;
 
-	hw_tbg_data = devm_kzalloc(&pdev->dev, sizeof(*hw_tbg_data)
-				   + sizeof(*hw_tbg_data->hws) * NUM_TBG,
+	hw_tbg_data = devm_kzalloc(&pdev->dev,
+				   struct_size(hw_tbg_data, hws, NUM_TBG),
 				   GFP_KERNEL);
 	if (!hw_tbg_data)
 		return -ENOMEM;

drivers/clk/qcom/clk-spmi-pmic-div.c

···
 	if (!nclks)
 		return -EINVAL;
 
-	cc = devm_kzalloc(dev, sizeof(*cc) + sizeof(*cc->clks) * nclks,
-			  GFP_KERNEL);
+	cc = devm_kzalloc(dev, struct_size(cc, clks, nclks), GFP_KERNEL);
 	if (!cc)
 		return -ENOMEM;
 	cc->nclks = nclks;

drivers/clk/samsung/clk-exynos-audss.c

···
 	epll = ERR_PTR(-ENODEV);
 
 	clk_data = devm_kzalloc(dev,
-				sizeof(*clk_data) +
-				sizeof(*clk_data->hws) * EXYNOS_AUDSS_MAX_CLKS,
+				struct_size(clk_data, hws,
+					    EXYNOS_AUDSS_MAX_CLKS),
 				GFP_KERNEL);
 	if (!clk_data)
 		return -ENOMEM;

drivers/clk/samsung/clk-exynos-clkout.c

···
 	int ret;
 	int i;
 
-	clkout = kzalloc(sizeof(*clkout) +
-			 sizeof(*clkout->data.hws) * EXYNOS_CLKOUT_NR_CLKS,
+	clkout = kzalloc(struct_size(clkout, data.hws, EXYNOS_CLKOUT_NR_CLKS),
 			 GFP_KERNEL);
 	if (!clkout)
 		return;

drivers/clk/samsung/clk-exynos5433.c

···
 
 	info = of_device_get_match_data(dev);
 
-	data = devm_kzalloc(dev, sizeof(*data) +
-			    sizeof(*data->ctx.clk_data.hws) * info->nr_clk_ids,
+	data = devm_kzalloc(dev,
+			    struct_size(data, ctx.clk_data.hws, info->nr_clk_ids),
 			    GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;

drivers/clk/samsung/clk-s3c2410-dclk.c

···
 	struct clk_hw **clk_table;
 	int ret, i;
 
-	s3c24xx_dclk = devm_kzalloc(&pdev->dev, sizeof(*s3c24xx_dclk) +
-			    sizeof(*s3c24xx_dclk->clk_data.hws) * DCLK_MAX_CLKS,
-			    GFP_KERNEL);
+	s3c24xx_dclk = devm_kzalloc(&pdev->dev,
+				    struct_size(s3c24xx_dclk, clk_data.hws,
+						DCLK_MAX_CLKS),
+				    GFP_KERNEL);
 	if (!s3c24xx_dclk)
 		return -ENOMEM;
 

drivers/clk/samsung/clk-s5pv210-audss.c

···
 	}
 
 	clk_data = devm_kzalloc(&pdev->dev,
-				sizeof(*clk_data) +
-				sizeof(*clk_data->hws) * AUDSS_MAX_CLKS,
+				struct_size(clk_data, hws, AUDSS_MAX_CLKS),
 				GFP_KERNEL);
 
 	if (!clk_data)

drivers/dax/device.c

···
 	if (!count)
 		return ERR_PTR(-EINVAL);
 
-	dev_dax = kzalloc(sizeof(*dev_dax) + sizeof(*res) * count, GFP_KERNEL);
+	dev_dax = kzalloc(struct_size(dev_dax, res, count), GFP_KERNEL);
 	if (!dev_dax)
 		return ERR_PTR(-ENOMEM);
 

drivers/dma/bcm-sba-raid.c

···
 
 	for (i = 0; i < sba->max_req; i++) {
 		req = devm_kzalloc(sba->dev,
-				sizeof(*req) +
-				sba->max_cmd_per_req * sizeof(req->cmds[0]),
-				GFP_KERNEL);
+				   struct_size(req, cmds, sba->max_cmd_per_req),
+				   GFP_KERNEL);
 		if (!req) {
 			ret = -ENOMEM;
 			goto fail_free_cmds_pool;

drivers/dma/edma.c

···
 		return NULL;
 	}
 
-	edesc = kzalloc(sizeof(*edesc) + sg_len * sizeof(edesc->pset[0]),
-			GFP_ATOMIC);
+	edesc = kzalloc(struct_size(edesc, pset, sg_len), GFP_ATOMIC);
 	if (!edesc)
 		return NULL;
 
···
 			nslots = 2;
 	}
 
-	edesc = kzalloc(sizeof(*edesc) + nslots * sizeof(edesc->pset[0]),
-			GFP_ATOMIC);
+	edesc = kzalloc(struct_size(edesc, pset, nslots), GFP_ATOMIC);
 	if (!edesc)
 		return NULL;
 
···
 		}
 	}
 
-	edesc = kzalloc(sizeof(*edesc) + nslots * sizeof(edesc->pset[0]),
-			GFP_ATOMIC);
+	edesc = kzalloc(struct_size(edesc, pset, nslots), GFP_ATOMIC);
 	if (!edesc)
 		return NULL;
 

drivers/dma/moxart-dma.c

···
 		return NULL;
 	}
 
-	d = kzalloc(sizeof(*d) + sg_len * sizeof(d->sg[0]), GFP_ATOMIC);
+	d = kzalloc(struct_size(d, sg, sg_len), GFP_ATOMIC);
 	if (!d)
 		return NULL;
 

drivers/dma/nbpfaxi.c

···
 	cfg = of_device_get_match_data(dev);
 	num_channels = cfg->num_channels;
 
-	nbpf = devm_kzalloc(dev, sizeof(*nbpf) + num_channels *
-			    sizeof(nbpf->chan[0]), GFP_KERNEL);
+	nbpf = devm_kzalloc(dev, struct_size(nbpf, chan, num_channels),
+			    GFP_KERNEL);
 	if (!nbpf)
 		return -ENOMEM;
 

drivers/dma/omap-dma.c

···
 	}
 
 	/* Now allocate and setup the descriptor. */
-	d = kzalloc(sizeof(*d) + sglen * sizeof(d->sg[0]), GFP_ATOMIC);
+	d = kzalloc(struct_size(d, sg, sglen), GFP_ATOMIC);
 	if (!d)
 		return NULL;
 

drivers/dma/sa11x0-dma.c

···
 		}
 	}
 
-	txd = kzalloc(sizeof(*txd) + j * sizeof(txd->sg[0]), GFP_ATOMIC);
+	txd = kzalloc(struct_size(txd, sg, j), GFP_ATOMIC);
 	if (!txd) {
 		dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
 		return NULL;
···
 	if (sglen == 0)
 		return NULL;
 
-	txd = kzalloc(sizeof(*txd) + sglen * sizeof(txd->sg[0]), GFP_ATOMIC);
+	txd = kzalloc(struct_size(txd, sg, sglen), GFP_ATOMIC);
 	if (!txd) {
 		dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
 		return NULL;

drivers/dma/sh/usb-dmac.c

···
 	struct usb_dmac_desc *desc;
 	unsigned long flags;
 
-	desc = kzalloc(sizeof(*desc) + sg_len * sizeof(desc->sg[0]), gfp);
+	desc = kzalloc(struct_size(desc, sg, sg_len), gfp);
 	if (!desc)
 		return -ENOMEM;
 

drivers/dma/sprd-dma.c

···
 		return ret;
 	}
 
-	sdev = devm_kzalloc(&pdev->dev, sizeof(*sdev) +
-			    sizeof(*dma_chn) * chn_count,
+	sdev = devm_kzalloc(&pdev->dev,
+			    struct_size(sdev, channels, chn_count),
 			    GFP_KERNEL);
 	if (!sdev)
 		return -ENOMEM;

drivers/firewire/core-topology.c

···
 {
 	struct fw_node *node;
 
-	node = kzalloc(sizeof(*node) + port_count * sizeof(node->ports[0]),
-		       GFP_ATOMIC);
+	node = kzalloc(struct_size(node, ports, port_count), GFP_ATOMIC);
 	if (node == NULL)
 		return NULL;
 

drivers/gpio/gpio-uniphier.c

···
 		return ret;
 
 	nregs = uniphier_gpio_get_nbanks(ngpios) * 2 + 3;
-	priv = devm_kzalloc(dev,
-			    sizeof(*priv) + sizeof(priv->saved_vals[0]) * nregs,
+	priv = devm_kzalloc(dev, struct_size(priv, saved_vals, nregs),
 			    GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

drivers/gpio/gpiolib.c

···
 	if (count < 0)
 		return ERR_PTR(count);
 
-	descs = kzalloc(sizeof(*descs) + sizeof(descs->desc[0]) * count,
-			GFP_KERNEL);
+	descs = kzalloc(struct_size(descs, desc, count), GFP_KERNEL);
 	if (!descs)
 		return ERR_PTR(-ENOMEM);
 

drivers/gpu/drm/nouveau/nvkm/core/ramht.c

···
 	struct nvkm_ramht *ramht;
 	int ret, i;
 
-	if (!(ramht = *pramht = vzalloc(sizeof(*ramht) +
-					(size >> 3) * sizeof(*ramht->data))))
+	if (!(ramht = *pramht = vzalloc(struct_size(ramht, data, (size >> 3)))))
 		return -ENOMEM;
 
 	ramht->device = device;

drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c

···
 
 		sdom = spec;
 		while (sdom->signal_nr) {
-			dom = kzalloc(sizeof(*dom) + sdom->signal_nr *
-				      sizeof(*dom->signal), GFP_KERNEL);
+			dom = kzalloc(struct_size(dom, signal, sdom->signal_nr),
+				      GFP_KERNEL);
 			if (!dom)
 				return -ENOMEM;
 

drivers/hwspinlock/omap_hwspinlock.c

···
 
 	num_locks = i * 32; /* actual number of locks in this device */
 
-	bank = kzalloc(sizeof(*bank) + num_locks * sizeof(*hwlock), GFP_KERNEL);
+	bank = kzalloc(struct_size(bank, lock, num_locks), GFP_KERNEL);
 	if (!bank) {
 		ret = -ENOMEM;
 		goto iounmap_base;

drivers/hwspinlock/sirf_hwspinlock.c

···
 	if (!pdev->dev.of_node)
 		return -ENODEV;
 
-	hwspin = devm_kzalloc(&pdev->dev, sizeof(*hwspin) +
-			sizeof(*hwlock) * HW_SPINLOCK_NUMBER, GFP_KERNEL);
+	hwspin = devm_kzalloc(&pdev->dev,
+			      struct_size(hwspin, bank.lock,
+					  HW_SPINLOCK_NUMBER),
+			      GFP_KERNEL);
 	if (!hwspin)
 		return -ENOMEM;
 

drivers/hwspinlock/u8500_hsem.c

···
 	/* clear all interrupts */
 	writel(0xFFFF, io_base + HSEM_ICRALL);
 
-	bank = kzalloc(sizeof(*bank) + num_locks * sizeof(*hwlock), GFP_KERNEL);
+	bank = kzalloc(struct_size(bank, lock, num_locks), GFP_KERNEL);
 	if (!bank) {
 		ret = -ENOMEM;
 		goto iounmap_base;

drivers/infiniband/core/cache.c

···
 			goto err;
 	}
 
-	pkey_cache = kmalloc(sizeof *pkey_cache + tprops->pkey_tbl_len *
-			     sizeof *pkey_cache->table, GFP_KERNEL);
+	pkey_cache = kmalloc(struct_size(pkey_cache, table,
+					 tprops->pkey_tbl_len),
+			     GFP_KERNEL);
 	if (!pkey_cache)
 		goto err;
 

drivers/infiniband/core/cm.c

···
 	int count = 0;
 	u8 i;
 
-	cm_dev = kzalloc(sizeof(*cm_dev) + sizeof(*port) *
-			 ib_device->phys_port_cnt, GFP_KERNEL);
+	cm_dev = kzalloc(struct_size(cm_dev, port, ib_device->phys_port_cnt),
+			 GFP_KERNEL);
 	if (!cm_dev)
 		return;
 

drivers/infiniband/core/multicast.c

···
 	int i;
 	int count = 0;
 
-	dev = kmalloc(sizeof *dev + device->phys_port_cnt * sizeof *port,
+	dev = kmalloc(struct_size(dev, port, device->phys_port_cnt),
 		      GFP_KERNEL);
 	if (!dev)
 		return;

drivers/infiniband/core/uverbs_cmd.c

···
 	struct ib_uflow_resources *resources;
 
 	resources =
-		kmalloc(sizeof(*resources) +
-			num_specs * sizeof(*resources->collection), GFP_KERNEL);
+		kmalloc(struct_size(resources, collection, num_specs),
+			GFP_KERNEL);
 
 	if (!resources)
 		return NULL;

drivers/infiniband/core/uverbs_ioctl_merge.c

···
 	if (max_attr_buckets >= 0)
 		num_attr_buckets = max_attr_buckets + 1;
 
-	method = kzalloc(sizeof(*method) +
-			 num_attr_buckets * sizeof(*method->attr_buckets),
+	method = kzalloc(struct_size(method, attr_buckets, num_attr_buckets),
 			 GFP_KERNEL);
 	if (!method)
 		return ERR_PTR(-ENOMEM);
···
 	if (max_method_buckets >= 0)
 		num_method_buckets = max_method_buckets + 1;
 
-	object = kzalloc(sizeof(*object) +
-			 num_method_buckets *
-			 sizeof(*object->method_buckets), GFP_KERNEL);
+	object = kzalloc(struct_size(object, method_buckets,
+				     num_method_buckets),
+			 GFP_KERNEL);
 	if (!object)
 		return ERR_PTR(-ENOMEM);
 
···
 		if (methods_max_bucket < 0)
 			continue;
 
-		hash = kzalloc(sizeof(*hash) +
-			       sizeof(*hash->methods) * (methods_max_bucket + 1),
+		hash = kzalloc(struct_size(hash, methods,
+					   methods_max_bucket + 1),
 			       GFP_KERNEL);
 		if (!hash) {
 			res = -ENOMEM;
···
 	if (max_object_buckets >= 0)
 		num_objects_buckets = max_object_buckets + 1;
 
-	root_spec = kzalloc(sizeof(*root_spec) +
-			    num_objects_buckets * sizeof(*root_spec->object_buckets),
+	root_spec = kzalloc(struct_size(root_spec, object_buckets,
+					num_objects_buckets),
 			    GFP_KERNEL);
 	if (!root_spec)
 		return ERR_PTR(-ENOMEM);
···
 		if (objects_max_bucket < 0)
 			continue;
 
-		hash = kzalloc(sizeof(*hash) +
-			       sizeof(*hash->objects) * (objects_max_bucket + 1),
+		hash = kzalloc(struct_size(hash, objects,
+					   objects_max_bucket + 1),
 			       GFP_KERNEL);
 		if (!hash) {
 			res = -ENOMEM;

drivers/infiniband/hw/mthca/mthca_memfree.c

···
 	obj_per_chunk = MTHCA_TABLE_CHUNK_SIZE / obj_size;
 	num_icm = DIV_ROUND_UP(nobj, obj_per_chunk);
 
-	table = kmalloc(sizeof *table + num_icm * sizeof *table->icm, GFP_KERNEL);
+	table = kmalloc(struct_size(table, icm, num_icm), GFP_KERNEL);
 	if (!table)
 		return NULL;
 
···
 		return NULL;
 
 	npages = dev->uar_table.uarc_size / MTHCA_ICM_PAGE_SIZE;
-	db_tab = kmalloc(sizeof *db_tab + npages * sizeof *db_tab->page, GFP_KERNEL);
+	db_tab = kmalloc(struct_size(db_tab, page, npages), GFP_KERNEL);
 	if (!db_tab)
 		return ERR_PTR(-ENOMEM);
 

drivers/infiniband/sw/rdmavt/mr.c

···
 
 	/* Allocate struct plus pointers to first level page tables. */
 	m = (count + RVT_SEGSZ - 1) / RVT_SEGSZ;
-	mr = kzalloc(sizeof(*mr) + m * sizeof(mr->mr.map[0]), GFP_KERNEL);
+	mr = kzalloc(struct_size(mr, mr.map, m), GFP_KERNEL);
 	if (!mr)
 		goto bail;
 
···
 
 	/* Allocate struct plus pointers to first level page tables. */
 	m = (fmr_attr->max_pages + RVT_SEGSZ - 1) / RVT_SEGSZ;
-	fmr = kzalloc(sizeof(*fmr) + m * sizeof(fmr->mr.map[0]), GFP_KERNEL);
+	fmr = kzalloc(struct_size(fmr, mr.map, m), GFP_KERNEL);
 	if (!fmr)
 		goto bail;
 

drivers/input/input-leds.c

···
 	if (!num_leds)
 		return -ENXIO;
 
-	leds = kzalloc(sizeof(*leds) + num_leds * sizeof(*leds->leds),
-		       GFP_KERNEL);
+	leds = kzalloc(struct_size(leds, leds, num_leds), GFP_KERNEL);
 	if (!leds)
 		return -ENOMEM;
 

drivers/input/input-mt.c

···
 	if (mt)
 		return mt->num_slots != num_slots ? -EINVAL : 0;
 
-	mt = kzalloc(sizeof(*mt) + num_slots * sizeof(*mt->slots), GFP_KERNEL);
+	mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL);
 	if (!mt)
 		goto err_mem;
 

drivers/input/keyboard/cap11xx.c

···
 	}
 
 	priv = devm_kzalloc(dev,
-			    sizeof(*priv) +
-				cap->num_channels * sizeof(priv->keycodes[0]),
+			    struct_size(priv, keycodes, cap->num_channels),
 			    GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

drivers/md/dm-raid.c

···
 		return ERR_PTR(-EINVAL);
 	}
 
-	rs = kzalloc(sizeof(*rs) + raid_devs * sizeof(rs->dev[0]), GFP_KERNEL);
+	rs = kzalloc(struct_size(rs, dev, raid_devs), GFP_KERNEL);
 	if (!rs) {
 		ti->error = "Cannot allocate raid context";
 		return ERR_PTR(-ENOMEM);

drivers/md/dm-table.c

···
  * On the other hand, dm-switch needs to process bulk data using messages and
  * excessive use of GFP_NOIO could cause trouble.
  */
-static char **realloc_argv(unsigned *array_size, char **old_argv)
+static char **realloc_argv(unsigned *size, char **old_argv)
 {
 	char **argv;
 	unsigned new_size;
 	gfp_t gfp;
 
-	if (*array_size) {
-		new_size = *array_size * 2;
+	if (*size) {
+		new_size = *size * 2;
 		gfp = GFP_KERNEL;
 	} else {
 		new_size = 8;
···
 	}
 	argv = kmalloc(new_size * sizeof(*argv), gfp);
 	if (argv) {
-		memcpy(argv, old_argv, *array_size * sizeof(*argv));
-		*array_size = new_size;
+		memcpy(argv, old_argv, *size * sizeof(*argv));
+		*size = new_size;
 	}
 
 	kfree(old_argv);

drivers/mfd/qcom-pm8xxx.c

···
 	pr_info("PMIC revision 2: %02X\n", val);
 	rev |= val << BITS_PER_BYTE;
 
-	chip = devm_kzalloc(&pdev->dev, sizeof(*chip) +
-			    sizeof(chip->config[0]) * data->num_irqs,
+	chip = devm_kzalloc(&pdev->dev,
+			    struct_size(chip, config, data->num_irqs),
 			    GFP_KERNEL);
 	if (!chip)
 		return -ENOMEM;

drivers/misc/cb710/core.c

···
 	if (val & CB710_SLOT_SM)
 		++n;
 
-	chip = devm_kzalloc(&pdev->dev,
-		sizeof(*chip) + n * sizeof(*chip->slot), GFP_KERNEL);
+	chip = devm_kzalloc(&pdev->dev, struct_size(chip, slot, n),
+			    GFP_KERNEL);
 	if (!chip)
 		return -ENOMEM;
 

drivers/misc/vexpress-syscfg.c

···
 		val = energy_quirk;
 	}
 
-	func = kzalloc(sizeof(*func) + sizeof(*func->template) * num,
-			GFP_KERNEL);
+	func = kzalloc(struct_size(func, template, num), GFP_KERNEL);
 	if (!func)
 		return ERR_PTR(-ENOMEM);
 

drivers/mtd/spi-nor/aspeed-smc.c

···
 		return -ENODEV;
 	info = match->data;
 
-	controller = devm_kzalloc(&pdev->dev, sizeof(*controller) +
-		info->nce * sizeof(controller->chips[0]), GFP_KERNEL);
+	controller = devm_kzalloc(&pdev->dev,
+				  struct_size(controller, chips, info->nce),
+				  GFP_KERNEL);
 	if (!controller)
 		return -ENOMEM;
 	controller->info = info;

drivers/net/can/peak_canfd/peak_pciefd_main.c

···
 		can_count = 1;
 
 	/* allocate board structure object */
-	pciefd = devm_kzalloc(&pdev->dev, sizeof(*pciefd) +
-			      can_count * sizeof(*pciefd->can),
+	pciefd = devm_kzalloc(&pdev->dev, struct_size(pciefd, can, can_count),
 			      GFP_KERNEL);
 	if (!pciefd) {
 		err = -ENOMEM;

drivers/net/ethernet/mellanox/mlx5/core/debugfs.c

···
 	int err;
 	int i;
 
-	d = kzalloc(sizeof(*d) + nfile * sizeof(d->fields[0]), GFP_KERNEL);
+	d = kzalloc(struct_size(d, fields, nfile), GFP_KERNEL);
 	if (!d)
 		return -ENOMEM;
 

drivers/net/ethernet/mellanox/mlx5/core/fs_core.c

···
 {
 	struct mlx5_flow_handle *handle;
 
-	handle = kzalloc(sizeof(*handle) + sizeof(handle->rule[0]) *
-			  num_rules, GFP_KERNEL);
+	handle = kzalloc(struct_size(handle, rule, num_rules), GFP_KERNEL);
 	if (!handle)
 		return NULL;
 

drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c

···
 
 			mvmsta = iwl_mvm_sta_from_mac80211(sta);
 			WARN_ON(rcu_access_pointer(mvmsta->ptk_pn[keyidx]));
-			ptk_pn = kzalloc(sizeof(*ptk_pn) +
-					 mvm->trans->num_rx_queues *
-						sizeof(ptk_pn->q[0]),
+			ptk_pn = kzalloc(struct_size(ptk_pn, q,
+						     mvm->trans->num_rx_queues),
 					 GFP_KERNEL);
 			if (!ptk_pn) {
 				ret = -ENOMEM;

drivers/net/wireless/mediatek/mt76/agg-rx.c

···
 
 	mt76_rx_aggr_stop(dev, wcid, tidno);
 
-	tid = kzalloc(sizeof(*tid) + size * sizeof(tid->reorder_buf[0]),
-		      GFP_KERNEL);
+	tid = kzalloc(struct_size(tid, reorder_buf, size), GFP_KERNEL);
 	if (!tid)
 		return -ENOMEM;
 

drivers/pinctrl/samsung/pinctrl-s3c64xx.c

···
 		++nr_domains;
 	}
 
-	data = devm_kzalloc(dev, sizeof(*data)
-			+ nr_domains * sizeof(*data->domains), GFP_KERNEL);
+	data = devm_kzalloc(dev, struct_size(data, domains, nr_domains),
+			    GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
 	data->drvdata = d;

drivers/pinctrl/uniphier/pinctrl-uniphier-core.c

···
 
 	nregs = DIV_ROUND_UP(count * width, 32);
 
-	region = devm_kzalloc(dev,
-			      sizeof(*region) + sizeof(region->vals[0]) * nregs,
+	region = devm_kzalloc(dev, struct_size(region, vals, nregs),
 			      GFP_KERNEL);
 	if (!region)
 		return -ENOMEM;

drivers/regulator/mc13783-regulator.c

···
 	if (num_regulators <= 0)
 		return -EINVAL;
 
-	priv = devm_kzalloc(&pdev->dev, sizeof(*priv) +
-			num_regulators * sizeof(priv->regulators[0]),
-			GFP_KERNEL);
+	priv = devm_kzalloc(&pdev->dev,
+			    struct_size(priv, regulators, num_regulators),
+			    GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 

drivers/regulator/mc13892-regulator.c

···
 	if (num_regulators <= 0)
 		return -EINVAL;
 
-	priv = devm_kzalloc(&pdev->dev, sizeof(*priv) +
-		num_regulators * sizeof(priv->regulators[0]),
-		GFP_KERNEL);
+	priv = devm_kzalloc(&pdev->dev,
+			    struct_size(priv, regulators, num_regulators),
+			    GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 

drivers/reset/core.c

···
 	if (num < 0)
 		return optional ? NULL : ERR_PTR(num);
 
-	resets = kzalloc(sizeof(*resets) + sizeof(resets->rstc[0]) * num,
-			 GFP_KERNEL);
+	resets = kzalloc(struct_size(resets, rstc, num), GFP_KERNEL);
 	if (!resets)
 		return ERR_PTR(-ENOMEM);
 

drivers/rtc/rtc-ac100.c

···
 	const char *parents[2] = {AC100_RTC_32K_NAME};
 	int i, ret;
 
-	chip->clk_data = devm_kzalloc(chip->dev, sizeof(*chip->clk_data) +
-						 sizeof(*chip->clk_data->hws) *
-						 AC100_CLKOUT_NUM,
-						 GFP_KERNEL);
+	chip->clk_data = devm_kzalloc(chip->dev,
+				      struct_size(chip->clk_data, hws,
+						  AC100_CLKOUT_NUM),
+				      GFP_KERNEL);
 	if (!chip->clk_data)
 		return -ENOMEM;
 

drivers/s390/cio/ccwgroup.c

···
 	if (num_devices < 1)
 		return -EINVAL;
 
-	gdev = kzalloc(sizeof(*gdev) + num_devices * sizeof(gdev->cdev[0]),
-		       GFP_KERNEL);
+	gdev = kzalloc(struct_size(gdev, cdev, num_devices), GFP_KERNEL);
 	if (!gdev)
 		return -ENOMEM;
 

drivers/soc/actions/owl-sps.c

···
 
 	sps_info = match->data;
 
-	sps = devm_kzalloc(&pdev->dev, sizeof(*sps) +
-			   sps_info->num_domains * sizeof(sps->domains[0]),
+	sps = devm_kzalloc(&pdev->dev,
+			   struct_size(sps, domains, sps_info->num_domains),
 			   GFP_KERNEL);
 	if (!sps)
 		return -ENOMEM;

drivers/soc/rockchip/pm_domains.c

···
 	pmu_info = match->data;
 
 	pmu = devm_kzalloc(dev,
-			   sizeof(*pmu) +
-				pmu_info->num_domains * sizeof(pmu->domains[0]),
+			   struct_size(pmu, domains, pmu_info->num_domains),
 			   GFP_KERNEL);
 	if (!pmu)
 		return -ENOMEM;

drivers/staging/greybus/module.c

···
 	struct gb_module *module;
 	int i;
 
-	module = kzalloc(sizeof(*module) + num_interfaces * sizeof(intf),
-				GFP_KERNEL);
+	module = kzalloc(struct_size(module, interfaces, num_interfaces),
+			 GFP_KERNEL);
 	if (!module)
 		return NULL;
 

drivers/thermal/qcom/tsens.c

···
 	int ret, i;
 	struct device *dev;
 	struct device_node *np;
-	struct tsens_sensor *s;
 	struct tsens_device *tmdev;
 	const struct tsens_data *data;
 	const struct of_device_id *id;
···
 		return -EINVAL;
 	}
 
-	tmdev = devm_kzalloc(dev, sizeof(*tmdev) +
-			     data->num_sensors * sizeof(*s), GFP_KERNEL);
+	tmdev = devm_kzalloc(dev,
+			     struct_size(tmdev, sensor, data->num_sensors),
+			     GFP_KERNEL);
 	if (!tmdev)
 		return -ENOMEM;
 

drivers/usb/gadget/function/f_midi.c

···
 	}
 
 	/* allocate and initialize one new instance */
-	midi = kzalloc(
-		sizeof(*midi) + opts->in_ports * sizeof(*midi->in_ports_array),
-		GFP_KERNEL);
+	midi = kzalloc(struct_size(midi, in_ports_array, opts->in_ports),
+		       GFP_KERNEL);
 	if (!midi) {
 		status = -ENOMEM;
 		goto setup_fail;

drivers/zorro/zorro.c

···
 	int error;
 
 	/* Initialize the Zorro bus */
-	bus = kzalloc(sizeof(*bus) +
-		      zorro_num_autocon * sizeof(bus->devices[0]),
+	bus = kzalloc(struct_size(bus, devices, zorro_num_autocon),
 		      GFP_KERNEL);
 	if (!bus)
 		return -ENOMEM;

fs/afs/addr_list.c

···
 
 	_enter("%u,%u,%u", nr, service, port);
 
-	alist = kzalloc(sizeof(*alist) + sizeof(alist->addrs[0]) * nr,
-			GFP_KERNEL);
+	alist = kzalloc(struct_size(alist, addrs, nr), GFP_KERNEL);
 	if (!alist)
 		return NULL;
 

include/linux/compiler-clang.h

···
 #ifdef __noretpoline
 #undef __noretpoline
 #endif
+
+/*
+ * Not all versions of clang implement the the type-generic versions
+ * of the builtin overflow checkers. Fortunately, clang implements
+ * __has_builtin allowing us to avoid awkward version
+ * checks. Unfortunately, we don't know which version of gcc clang
+ * pretends to be, so the macro may or may not be defined.
+ */
+#undef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW
+#if __has_builtin(__builtin_mul_overflow) && \
+    __has_builtin(__builtin_add_overflow) && \
+    __has_builtin(__builtin_sub_overflow)
+#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
+#endif

include/linux/compiler-gcc.h

···
  * code
  */
 #define uninitialized_var(x) x = x
+
+#if GCC_VERSION >= 50100
+#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
+#endif

include/linux/compiler-intel.h

···
 #define __builtin_bswap16 _bswap16
 #endif
 
+/*
+ * icc defines __GNUC__, but does not implement the builtin overflow checkers.
+ */
+#undef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW

include/linux/device.h

···
 #include <linux/ratelimit.h>
 #include <linux/uidgid.h>
 #include <linux/gfp.h>
+#include <linux/overflow.h>
 #include <asm/device.h>
 
 struct device;
···
 static inline void *devm_kmalloc_array(struct device *dev,
 				       size_t n, size_t size, gfp_t flags)
 {
-	if (size != 0 && n > SIZE_MAX / size)
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow(n, size, &bytes)))
 		return NULL;
-	return devm_kmalloc(dev, n * size, flags);
+
+	return devm_kmalloc(dev, bytes, flags);
 }
 static inline void *devm_kcalloc(struct device *dev,
 				 size_t n, size_t size, gfp_t flags)

include/linux/mm.h

···
 #include <linux/err.h>
 #include <linux/page_ref.h>
 #include <linux/memremap.h>
+#include <linux/overflow.h>
 
 struct mempolicy;
 struct anon_vma;
···
 
 static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags)
 {
-	if (size != 0 && n > SIZE_MAX / size)
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow(n, size, &bytes)))
 		return NULL;
 
-	return kvmalloc(n * size, flags);
+	return kvmalloc(bytes, flags);
 }
 
 extern void kvfree(const void *addr);

include/linux/overflow.h

···
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+#ifndef __LINUX_OVERFLOW_H
+#define __LINUX_OVERFLOW_H
+
+#include <linux/compiler.h>
+
+/*
+ * In the fallback code below, we need to compute the minimum and
+ * maximum values representable in a given type. These macros may also
+ * be useful elsewhere, so we provide them outside the
+ * COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW block.
+ *
+ * It would seem more obvious to do something like
+ *
+ * #define type_min(T) (T)(is_signed_type(T) ? (T)1 << (8*sizeof(T)-1) : 0)
+ * #define type_max(T) (T)(is_signed_type(T) ? ((T)1 << (8*sizeof(T)-1)) - 1 : ~(T)0)
+ *
+ * Unfortunately, the middle expressions, strictly speaking, have
+ * undefined behaviour, and at least some versions of gcc warn about
+ * the type_max expression (but not if -fsanitize=undefined is in
+ * effect; in that case, the warning is deferred to runtime...).
+ *
+ * The slightly excessive casting in type_min is to make sure the
+ * macros also produce sensible values for the exotic type _Bool. [The
+ * overflow checkers only almost work for _Bool, but that's
+ * a-feature-not-a-bug, since people shouldn't be doing arithmetic on
+ * _Bools. Besides, the gcc builtins don't allow _Bool* as third
+ * argument.]
+ *
+ * Idea stolen from
+ * https://mail-index.netbsd.org/tech-misc/2007/02/05/0000.html -
+ * credit to Christian Biere.
+ */
+#define is_signed_type(type)       (((type)(-1)) < (type)1)
+#define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type)))
+#define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T)))
+#define type_min(T) ((T)((T)-type_max(T)-(T)1))
+
+
+#ifdef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW
+/*
+ * For simplicity and code hygiene, the fallback code below insists on
+ * a, b and *d having the same type (similar to the min() and max()
+ * macros), whereas gcc's type-generic overflow checkers accept
+ * different types. Hence we don't just make check_add_overflow an
+ * alias for __builtin_add_overflow, but add type checks similar to
+ * below.
+ */
+#define check_add_overflow(a, b, d) ({		\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	typeof(d) __d = (d);			\
+	(void) (&__a == &__b);			\
+	(void) (&__a == __d);			\
+	__builtin_add_overflow(__a, __b, __d);	\
+})
+
+#define check_sub_overflow(a, b, d) ({		\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	typeof(d) __d = (d);			\
+	(void) (&__a == &__b);			\
+	(void) (&__a == __d);			\
+	__builtin_sub_overflow(__a, __b, __d);	\
+})
+
+#define check_mul_overflow(a, b, d) ({		\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	typeof(d) __d = (d);			\
+	(void) (&__a == &__b);			\
+	(void) (&__a == __d);			\
+	__builtin_mul_overflow(__a, __b, __d);	\
+})
+
+#else
+
+
+/* Checking for unsigned overflow is relatively easy without causing UB. */
+#define __unsigned_add_overflow(a, b, d) ({	\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	typeof(d) __d = (d);			\
+	(void) (&__a == &__b);			\
+	(void) (&__a == __d);			\
+	*__d = __a + __b;			\
+	*__d < __a;				\
+})
+#define __unsigned_sub_overflow(a, b, d) ({	\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	typeof(d) __d = (d);			\
+	(void) (&__a == &__b);			\
+	(void) (&__a == __d);			\
+	*__d = __a - __b;			\
+	__a < __b;				\
+})
+/*
+ * If one of a or b is a compile-time constant, this avoids a division.
+ */
+#define __unsigned_mul_overflow(a, b, d) ({		\
+	typeof(a) __a = (a);				\
+	typeof(b) __b = (b);				\
+	typeof(d) __d = (d);				\
+	(void) (&__a == &__b);				\
+	(void) (&__a == __d);				\
+	*__d = __a * __b;				\
+	__builtin_constant_p(__b) ?			\
+	  __b > 0 && __a > type_max(typeof(__a)) / __b : \
+	  __a > 0 && __b > type_max(typeof(__b)) / __a;	 \
+})
+
+/*
+ * For signed types, detecting overflow is much harder, especially if
+ * we want to avoid UB. But the interface of these macros is such that
+ * we must provide a result in *d, and in fact we must produce the
+ * result promised by gcc's builtins, which is simply the possibly
+ * wrapped-around value. Fortunately, we can just formally do the
+ * operations in the widest relevant unsigned type (u64) and then
+ * truncate the result - gcc is smart enough to generate the same code
+ * with and without the (u64) casts.
+ */
+
+/*
+ * Adding two signed integers can overflow only if they have the same
+ * sign, and overflow has happened iff the result has the opposite
+ * sign.
+ */
+#define __signed_add_overflow(a, b, d) ({	\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	typeof(d) __d = (d);			\
+	(void) (&__a == &__b);			\
+	(void) (&__a == __d);			\
+	*__d = (u64)__a + (u64)__b;		\
+	(((~(__a ^ __b)) & (*__d ^ __a))	\
+		& type_min(typeof(__a))) != 0;	\
+})
+
+/*
+ * Subtraction is similar, except that overflow can now happen only
+ * when the signs are opposite. In this case, overflow has happened if
+ * the result has the opposite sign of a.
+ */
+#define __signed_sub_overflow(a, b, d) ({	\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	typeof(d) __d = (d);			\
+	(void) (&__a == &__b);			\
+	(void) (&__a == __d);			\
+	*__d = (u64)__a - (u64)__b;		\
+	((((__a ^ __b)) & (*__d ^ __a))		\
+		& type_min(typeof(__a))) != 0;	\
+})
+
+/*
+ * Signed multiplication is rather hard. gcc always follows C99, so
+ * division is truncated towards 0. This means that we can write the
+ * overflow check like this:
+ *
+ * (a > 0 && (b > MAX/a || b < MIN/a)) ||
+ * (a < -1 && (b > MIN/a || b < MAX/a) ||
+ * (a == -1 && b == MIN)
+ *
+ * The redundant casts of -1 are to silence an annoying -Wtype-limits
+ * (included in -Wextra) warning: When the type is u8 or u16, the
+ * __b_c_e in check_mul_overflow obviously selects
+ * __unsigned_mul_overflow, but unfortunately gcc still parses this
+ * code and warns about the limited range of __b.
+ */
+
+#define __signed_mul_overflow(a, b, d) ({				\
+	typeof(a) __a = (a);						\
+	typeof(b) __b = (b);						\
+	typeof(d) __d = (d);						\
+	typeof(a) __tmax = type_max(typeof(a));				\
+	typeof(a) __tmin = type_min(typeof(a));				\
+	(void) (&__a == &__b);						\
+	(void) (&__a == __d);						\
+	*__d = (u64)__a * (u64)__b;					\
+	(__b > 0   && (__a > __tmax/__b || __a < __tmin/__b)) ||	\
+	(__b < (typeof(__b))-1  && (__a > __tmin/__b || __a < __tmax/__b)) || \
+	(__b == (typeof(__b))-1 && __a == __tmin);			\
+})
+
+
+#define check_add_overflow(a, b, d)					\
+	__builtin_choose_expr(is_signed_type(typeof(a)),		\
+			__signed_add_overflow(a, b, d),			\
+			__unsigned_add_overflow(a, b, d))
+
+#define check_sub_overflow(a, b, d)					\
+	__builtin_choose_expr(is_signed_type(typeof(a)),		\
+			__signed_sub_overflow(a, b, d),			\
+			__unsigned_sub_overflow(a, b, d))
+
+#define check_mul_overflow(a, b, d)					\
+	__builtin_choose_expr(is_signed_type(typeof(a)),		\
+			__signed_mul_overflow(a, b, d),			\
+			__unsigned_mul_overflow(a, b, d))
+
+
+#endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
+
+/**
+ * array_size() - Calculate size of 2-dimensional array.
+ *
+ * @a: dimension one
+ * @b: dimension two
+ *
+ * Calculates size of 2-dimensional array: @a * @b.
+ *
+ * Returns: number of bytes needed to represent the array or SIZE_MAX on
+ * overflow.
+ */
+static inline __must_check size_t array_size(size_t a, size_t b)
+{
+	size_t bytes;
+
+	if (check_mul_overflow(a, b, &bytes))
+		return SIZE_MAX;
+
+	return bytes;
+}
+
+/**
+ * array3_size() - Calculate size of 3-dimensional array.
+ *
+ * @a: dimension one
+ * @b: dimension two
+ * @c: dimension three
+ *
+ * Calculates size of 3-dimensional array: @a * @b * @c.
+ *
+ * Returns: number of bytes needed to represent the array or SIZE_MAX on
+ * overflow.
+ */
+static inline __must_check size_t array3_size(size_t a, size_t b, size_t c)
+{
+	size_t bytes;
+
+	if (check_mul_overflow(a, b, &bytes))
+		return SIZE_MAX;
+	if (check_mul_overflow(bytes, c, &bytes))
+		return SIZE_MAX;
+
+	return bytes;
+}
+
+static inline __must_check size_t __ab_c_size(size_t n, size_t size, size_t c)
+{
+	size_t bytes;
+
+	if (check_mul_overflow(n, size, &bytes))
+		return SIZE_MAX;
+	if (check_add_overflow(bytes, c, &bytes))
+		return SIZE_MAX;
+
+	return bytes;
+}
+
+/**
+ * struct_size() - Calculate size of structure with trailing array.
+ * @p: Pointer to the structure.
+ * @member: Name of the array member.
+ * @n: Number of elements in the array.
+ *
+ * Calculates size of memory needed for structure @p followed by an
+ * array of @n @member elements.
+ *
+ * Return: number of bytes needed or SIZE_MAX on overflow.
+ */
+#define struct_size(p, member, n)					\
+	__ab_c_size(n,							\
+		    sizeof(*(p)->member) + __must_be_array((p)->member),\
+		    sizeof(*(p)))
+
+#endif /* __LINUX_OVERFLOW_H */

include/linux/slab.h

···
 #define	_LINUX_SLAB_H
 
 #include <linux/gfp.h>
+#include <linux/overflow.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
 
···
  */
 static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
 {
-	if (size != 0 && n > SIZE_MAX / size)
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow(n, size, &bytes)))
 		return NULL;
 	if (__builtin_constant_p(n) && __builtin_constant_p(size))
-		return kmalloc(n * size, flags);
-	return __kmalloc(n * size, flags);
+		return kmalloc(bytes, flags);
+	return __kmalloc(bytes, flags);
 }
 
 /**
···
 static inline void *kmalloc_array_node(size_t n, size_t size, gfp_t flags,
 				       int node)
 {
-	if (size != 0 && n > SIZE_MAX / size)
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow(n, size, &bytes)))
 		return NULL;
 	if (__builtin_constant_p(n) && __builtin_constant_p(size))
-		return kmalloc_node(n * size, flags, node);
-	return __kmalloc_node(n * size, flags, node);
+		return kmalloc_node(bytes, flags, node);
+	return __kmalloc_node(bytes, flags, node);
 }
 
 static inline void *kcalloc_node(size_t n, size_t size, gfp_t flags, int node)

include/linux/vmalloc.h

···
 #include <linux/llist.h>
 #include <asm/page.h>		/* pgprot_t */
 #include <linux/rbtree.h>
+#include <linux/overflow.h>
 
 struct vm_area_struct;		/* vma defining user mapping in mm_types.h */
 struct notifier_block;		/* in notifier.h */

kernel/cgroup/cgroup.c

···
 	int ret;
 
 	/* allocate the cgroup and its ID, 0 is reserved for the root */
-	cgrp = kzalloc(sizeof(*cgrp) +
-		       sizeof(cgrp->ancestor_ids[0]) * (level + 1), GFP_KERNEL);
+	cgrp = kzalloc(struct_size(cgrp, ancestor_ids, (level + 1)),
+		       GFP_KERNEL);
 	if (!cgrp)
 		return ERR_PTR(-ENOMEM);
 

kernel/module.c

···
 	if (notes == 0)
 		return;
 
-	notes_attrs = kzalloc(sizeof(*notes_attrs)
-			      + notes * sizeof(notes_attrs->attrs[0]),
+	notes_attrs = kzalloc(struct_size(notes_attrs, attrs, notes),
 			      GFP_KERNEL);
 	if (notes_attrs == NULL)
 		return;

kernel/workqueue.c

···
 
 	lockdep_assert_held(&wq_pool_mutex);
 
-	ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
-		      GFP_KERNEL);
+	ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
 
 	new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
 	tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);

lib/Kconfig.debug

···
 config TEST_UUID
 	tristate "Test functions located in the uuid module at runtime"
 
+config TEST_OVERFLOW
+	tristate "Test check_*_overflow() functions at runtime"
+
 config TEST_RHASHTABLE
 	tristate "Perform selftest on resizable hash table"
 	default n

lib/Makefile

···
 obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
 obj-$(CONFIG_TEST_LIST_SORT) += test_list_sort.o
 obj-$(CONFIG_TEST_LKM) += test_module.o
+obj-$(CONFIG_TEST_OVERFLOW) += test_overflow.o
 obj-$(CONFIG_TEST_RHASHTABLE) += test_rhashtable.o
 obj-$(CONFIG_TEST_SORT) += test_sort.o
 obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o

lib/test_overflow.c

···
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Test cases for arithmetic overflow checks.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/overflow.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+
+#define DEFINE_TEST_ARRAY(t)			\
+	static const struct test_ ## t {	\
+		t a, b;				\
+		t sum, diff, prod;		\
+		bool s_of, d_of, p_of;		\
+	} t ## _tests[] __initconst
+
+DEFINE_TEST_ARRAY(u8) = {
+	{0, 0, 0, 0, 0, false, false, false},
+	{1, 1, 2, 0, 1, false, false, false},
+	{0, 1, 1, U8_MAX, 0, false, true, false},
+	{1, 0, 1, 1, 0, false, false, false},
+	{0, U8_MAX, U8_MAX, 1, 0, false, true, false},
+	{U8_MAX, 0, U8_MAX, U8_MAX, 0, false, false, false},
+	{1, U8_MAX, 0, 2, U8_MAX, true, true, false},
+	{U8_MAX, 1, 0, U8_MAX-1, U8_MAX, true, false, false},
+	{U8_MAX, U8_MAX, U8_MAX-1, 0, 1, true, false, true},
+
+	{U8_MAX, U8_MAX-1, U8_MAX-2, 1, 2, true, false, true},
+	{U8_MAX-1, U8_MAX, U8_MAX-2, U8_MAX, 2, true, true, true},
+
+	{1U << 3, 1U << 3, 1U << 4, 0, 1U << 6, false, false, false},
+	{1U << 4, 1U << 4, 1U << 5, 0, 0, false, false, true},
+	{1U << 4, 1U << 3, 3*(1U << 3), 1U << 3, 1U << 7, false, false, false},
+	{1U << 7, 1U << 7, 0, 0, 0, true, false, true},
+
+	{48, 32, 80, 16, 0, false, false, true},
+	{128, 128, 0, 0, 0, true, false, true},
+	{123, 234, 101, 145, 110, true, true, true},
+};
+DEFINE_TEST_ARRAY(u16) = {
+	{0, 0, 0, 0, 0, false, false, false},
+	{1, 1, 2, 0, 1, false, false, false},
+	{0, 1, 1, U16_MAX, 0, false, true, false},
+	{1, 0, 1, 1, 0, false, false, false},
+	{0, U16_MAX, U16_MAX, 1, 0, false, true, false},
+	{U16_MAX, 0, U16_MAX, U16_MAX, 0, false, false, false},
+	{1, U16_MAX, 0, 2, U16_MAX, true, true, false},
+	{U16_MAX, 1, 0, U16_MAX-1, U16_MAX, true, false, false},
+	{U16_MAX, U16_MAX, U16_MAX-1, 0, 1, true, false, true},
+
+	{U16_MAX, U16_MAX-1, U16_MAX-2, 1, 2, true, false, true},
+	{U16_MAX-1, U16_MAX, U16_MAX-2, U16_MAX, 2, true, true, true},
+
+	{1U << 7, 1U << 7, 1U << 8, 0, 1U << 14, false, false, false},
+	{1U << 8, 1U << 8, 1U << 9, 0, 0, false, false, true},
+	{1U << 8, 1U << 7, 3*(1U << 7), 1U << 7, 1U << 15, false, false, false},
+	{1U << 15, 1U << 15, 0, 0, 0, true, false, true},
+
+	{123, 234, 357, 65425, 28782, false, true, false},
+	{1234, 2345, 3579, 64425, 10146, false, true, true},
+};
+DEFINE_TEST_ARRAY(u32) = {
+	{0, 0, 0, 0, 0, false, false, false},
+	{1, 1, 2, 0, 1, false, false, false},
+	{0, 1, 1, U32_MAX, 0, false, true, false},
+	{1, 0, 1, 1, 0, false, false, false},
+	{0, U32_MAX, U32_MAX, 1, 0, false, true, false},
+	{U32_MAX, 0, U32_MAX, U32_MAX, 0, false, false, false},
+	{1, U32_MAX, 0, 2, U32_MAX, true, true, false},
+	{U32_MAX, 1, 0, U32_MAX-1, U32_MAX, true, false, false},
+	{U32_MAX, U32_MAX, U32_MAX-1, 0, 1, true, false, true},
+
+	{U32_MAX, U32_MAX-1, U32_MAX-2, 1, 2, true, false, true},
+	{U32_MAX-1, U32_MAX, U32_MAX-2, U32_MAX, 2, true, true, true},
+
+	{1U << 15, 1U << 15, 1U << 16, 0, 1U << 30, false, false, false},
+	{1U << 16, 1U << 16, 1U << 17, 0, 0, false, false, true},
+	{1U << 16, 1U << 15, 3*(1U << 15), 1U << 15, 1U << 31, false, false, false},
+	{1U << 31, 1U << 31, 0, 0, 0, true, false, true},
+
+	{-2U, 1U, -1U, -3U, -2U, false, false, false},
+	{-4U, 5U, 1U, -9U, -20U, true, false, true},
+};
+
+DEFINE_TEST_ARRAY(u64) = {
+	{0, 0, 0, 0, 0, false, false, false},
+	{1, 1, 2, 0, 1, false, false, false},
+	{0, 1, 1, U64_MAX, 0, false, true, false},
+	{1, 0, 1, 1, 0, false, false, false},
+	{0, U64_MAX, U64_MAX, 1, 0, false, true, false},
+	{U64_MAX, 0, U64_MAX, U64_MAX, 0, false, false, false},
+	{1, U64_MAX, 0, 2, U64_MAX, true, true, false},
+	{U64_MAX, 1, 0, U64_MAX-1, U64_MAX, true, false, false},
+	{U64_MAX, U64_MAX, U64_MAX-1, 0, 1, true, false, true},
+
+	{U64_MAX, U64_MAX-1, U64_MAX-2, 1, 2, true, false, true},
+	{U64_MAX-1, U64_MAX, U64_MAX-2, U64_MAX, 2, true, true, true},
+
+	{1ULL << 31, 1ULL << 31, 1ULL << 32, 0, 1ULL << 62, false, false, false},
+	{1ULL << 32, 1ULL << 32, 1ULL << 33, 0, 0, false, false, true},
+	{1ULL << 32, 1ULL << 31, 3*(1ULL << 31), 1ULL << 31, 1ULL << 63, false, false, false},
+	{1ULL << 63, 1ULL << 63, 0, 0, 0, true, false, true},
+	{1000000000ULL /* 10^9 */, 10000000000ULL /* 10^10 */,
+	 11000000000ULL, 18446744064709551616ULL, 10000000000000000000ULL,
+	 false, true, false},
+	{-15ULL, 10ULL, -5ULL, -25ULL, -150ULL, false, false, true},
+};
+
+DEFINE_TEST_ARRAY(s8) = {
+	{0, 0, 0, 0, 0, false, false, false},
+
+	{0, S8_MAX, S8_MAX, -S8_MAX, 0, false, false, false},
+	{S8_MAX, 0, S8_MAX, S8_MAX, 0, false, false, false},
+	{0, S8_MIN, S8_MIN, S8_MIN, 0, false, true, false},
+	{S8_MIN, 0, S8_MIN, S8_MIN, 0, false, false, false},
+
+	{-1, S8_MIN, S8_MAX, S8_MAX, S8_MIN, true, false, true},
+	{S8_MIN, -1, S8_MAX, -S8_MAX, S8_MIN, true, false, true},
+	{-1, S8_MAX, S8_MAX-1, S8_MIN, -S8_MAX, false, false, false},
+	{S8_MAX, -1, S8_MAX-1, S8_MIN, -S8_MAX, false, true, false},
+	{-1, -S8_MAX, S8_MIN, S8_MAX-1, S8_MAX, false, false, false},
+	{-S8_MAX, -1, S8_MIN, S8_MIN+2, S8_MAX, false, false, false},
+
+	{1, S8_MIN, -S8_MAX, -S8_MAX, S8_MIN, false, true, false},
+	{S8_MIN, 1, -S8_MAX, S8_MAX, S8_MIN, false, true, false},
+	{1, S8_MAX, S8_MIN, S8_MIN+2, S8_MAX, true, false, false},
+	{S8_MAX, 1, S8_MIN, S8_MAX-1, S8_MAX, true, false, false},
+
+	{S8_MIN, S8_MIN, 0, 0, 0, true, false, true},
+	{S8_MAX, S8_MAX, -2, 0, 1, true, false, true},
+
+	{-4, -32, -36, 28, -128, false, false, true},
+	{-4, 32, 28, -36, -128, false, false, false},
+};
+
+DEFINE_TEST_ARRAY(s16) = {
+	{0, 0, 0, 0, 0, false, false, false},
+
+	{0, S16_MAX, S16_MAX, -S16_MAX, 0, false, false, false},
+	{S16_MAX, 0, S16_MAX, S16_MAX, 0, false, false, false},
+	{0, S16_MIN, S16_MIN, S16_MIN, 0, false, true, false},
+	{S16_MIN, 0, S16_MIN, S16_MIN, 0, false, false, false},
+
+	{-1, S16_MIN, S16_MAX, S16_MAX, S16_MIN, true, false, true},
+	{S16_MIN, -1, S16_MAX, -S16_MAX, S16_MIN, true, false, true},
+	{-1, S16_MAX, S16_MAX-1, S16_MIN, -S16_MAX, false, false, false},
+	{S16_MAX, -1, S16_MAX-1, S16_MIN, -S16_MAX, false, true, false},
+	{-1, -S16_MAX, S16_MIN, S16_MAX-1, S16_MAX, false, false, false},
+	{-S16_MAX, -1, S16_MIN, S16_MIN+2, S16_MAX, false, false, false},
+
+	{1, S16_MIN, -S16_MAX, -S16_MAX, S16_MIN, false, true, false},
+	{S16_MIN, 1, -S16_MAX, S16_MAX, S16_MIN, false, true, false},
+	{1, S16_MAX, S16_MIN, S16_MIN+2, S16_MAX, true, false, false},
+	{S16_MAX, 1, S16_MIN, S16_MAX-1, S16_MAX, true, false, false},
+
+	{S16_MIN, S16_MIN, 0, 0, 0, true, false, true},
+	{S16_MAX, S16_MAX, -2, 0, 1, true, false, true},
+};
+DEFINE_TEST_ARRAY(s32) = {
+	{0, 0, 0, 0, 0, false, false, false},
+
+	{0, S32_MAX, S32_MAX, -S32_MAX, 0, false, false, false},
+	{S32_MAX, 0, S32_MAX, S32_MAX, 0, false, false, false},
+	{0, S32_MIN, S32_MIN, S32_MIN, 0, false, true, false},
+	{S32_MIN, 0, S32_MIN, S32_MIN, 0, false, false, false},
+
+	{-1, S32_MIN, S32_MAX, S32_MAX, S32_MIN, true, false, true},
+	{S32_MIN, -1, S32_MAX, -S32_MAX, S32_MIN, true, false, true},
+	{-1, S32_MAX, S32_MAX-1, S32_MIN, -S32_MAX, false, false, false},
+	{S32_MAX, -1, S32_MAX-1, S32_MIN, -S32_MAX, false, true, false},
+	{-1, -S32_MAX, S32_MIN, S32_MAX-1, S32_MAX, false, false, false},
+	{-S32_MAX, -1, S32_MIN, S32_MIN+2, S32_MAX, false, false, false},
+
+	{1, S32_MIN, -S32_MAX, -S32_MAX, S32_MIN, false, true, false},
+	{S32_MIN, 1, -S32_MAX, S32_MAX, S32_MIN, false, true, false},
+	{1, S32_MAX, S32_MIN, S32_MIN+2, S32_MAX, true, false, false},
+	{S32_MAX, 1, S32_MIN, S32_MAX-1, S32_MAX, true, false, false},
+
+	{S32_MIN, S32_MIN, 0, 0, 0, true, false, true},
+	{S32_MAX, S32_MAX, -2, 0, 1, true, false, true},
+};
+DEFINE_TEST_ARRAY(s64) = {
+	{0, 0, 0, 0, 0, false, false, false},
+
+	{0, S64_MAX, S64_MAX, -S64_MAX, 0, false, false, false},
+	{S64_MAX, 0, S64_MAX, S64_MAX, 0, false, false, false},
+	{0, S64_MIN, S64_MIN, S64_MIN, 0, false, true, false},
+	{S64_MIN, 0, S64_MIN, S64_MIN, 0, false, false, false},
+
+	{-1, S64_MIN, S64_MAX, S64_MAX, S64_MIN, true, false, true},
+	{S64_MIN, -1, S64_MAX, -S64_MAX, S64_MIN, true, false, true},
+	{-1, S64_MAX, S64_MAX-1, S64_MIN, -S64_MAX, false, false, false},
+	{S64_MAX, -1, S64_MAX-1, S64_MIN, -S64_MAX, false, true, false},
+	{-1, -S64_MAX, S64_MIN, S64_MAX-1, S64_MAX, false, false, false},
+	{-S64_MAX, -1, S64_MIN, S64_MIN+2, S64_MAX, false, false, false},
+
+	{1, S64_MIN, -S64_MAX, -S64_MAX, S64_MIN, false, true, false},
+	{S64_MIN, 1, -S64_MAX, S64_MAX, S64_MIN, false, true, false},
+	{1, S64_MAX, S64_MIN, S64_MIN+2, S64_MAX, true, false, false},
+	{S64_MAX, 1, S64_MIN, S64_MAX-1, S64_MAX, true, false, false},
+
+	{S64_MIN, S64_MIN, 0, 0, 0, true, false, true},
+	{S64_MAX, S64_MAX, -2, 0, 1, true, false, true},
+
+	{-1, -1, -2, 0, 1, false, false, false},
+	{-1, -128, -129, 127, 128, false, false, false},
+	{-128, -1, -129, -127, 128, false, false, false},
+	{0, -S64_MAX, -S64_MAX, S64_MAX, 0, false, false, false},
+};
+
+#define check_one_op(t, fmt, op, sym, a, b, r, of) do {		\
+	t _r;							\
+	bool _of;						\
+								\
+	_of = check_ ## op ## _overflow(a, b, &_r);		\
+	if (_of != of) {					\
+		pr_warn("expected "fmt" "sym" "fmt		\
+			" to%s overflow (type %s)\n",		\
+			a, b, of ? "" : " not", #t);		\
+		err = 1;					\
+	}							\
+	if (_r != r) {						\
+		pr_warn("expected "fmt" "sym" "fmt" == "	\
+			fmt", got "fmt" (type %s)\n",		\
+			a, b, r, _r, #t);			\
+		err = 1;					\
+	}							\
+} while (0)
+
+#define DEFINE_TEST_FUNC(t, fmt)					\
+static int __init do_test_ ## t(const struct test_ ## t *p)		\
+{							   		\
+	int err = 0;							\
+									\
+	check_one_op(t, fmt, add, "+", p->a, p->b, p->sum, p->s_of);	\
+	check_one_op(t, fmt, add, "+", p->b, p->a, p->sum, p->s_of);	\
+	check_one_op(t, fmt, sub, "-", p->a, p->b, p->diff, p->d_of);	\
+	check_one_op(t, fmt, mul, "*", p->a, p->b, p->prod, p->p_of);	\
+	check_one_op(t, fmt, mul, "*", p->b, p->a, p->prod, p->p_of);	\
+									\
+	return err;							\
+}									\
+									\
+static int __init test_ ## t ## _overflow(void) {			\
+	int err = 0;							\
+	unsigned i;							\
+									\
+	pr_info("%-3s: %zu tests\n", #t, ARRAY_SIZE(t ## _tests));	\
+	for (i = 0; i < ARRAY_SIZE(t ## _tests); ++i)			\
+		err |= do_test_ ## t(&t ## _tests[i]);			\
+	return err;							\
+}
+
+DEFINE_TEST_FUNC(u8, "%d");
+DEFINE_TEST_FUNC(s8, "%d");
+DEFINE_TEST_FUNC(u16, "%d");
+DEFINE_TEST_FUNC(s16, "%d");
+DEFINE_TEST_FUNC(u32, "%u");
+DEFINE_TEST_FUNC(s32, "%d");
+#if BITS_PER_LONG == 64
+DEFINE_TEST_FUNC(u64, "%llu");
+DEFINE_TEST_FUNC(s64, "%lld");
+#endif
+
+static int __init test_overflow_calculation(void)
+{
+	int err = 0;
+
+	err |= test_u8_overflow();
+	err |= test_s8_overflow();
+	err |= test_u16_overflow();
+	err |= test_s16_overflow();
+	err |= test_u32_overflow();
+	err |= test_s32_overflow();
+#if BITS_PER_LONG == 64
+	err |= test_u64_overflow();
+	err |= test_s64_overflow();
+#endif
+
+	return err;
+}
+
+/*
+ * Deal with the various forms of allocator arguments. See comments above
+ * the DEFINE_TEST_ALLOC() instances for mapping of the "bits".
+ */
+#define alloc010(alloc, arg, sz) alloc(sz, GFP_KERNEL)
+#define alloc011(alloc, arg, sz) alloc(sz, GFP_KERNEL, NUMA_NO_NODE)
+#define alloc000(alloc, arg, sz) alloc(sz)
+#define alloc001(alloc, arg, sz) alloc(sz, NUMA_NO_NODE)
+#define alloc110(alloc, arg, sz) alloc(arg, sz, GFP_KERNEL)
+#define free0(free, arg, ptr)	 free(ptr)
+#define free1(free, arg, ptr)	 free(arg, ptr)
+
+/* Wrap around to 8K */
+#define TEST_SIZE		(9 << PAGE_SHIFT)
+
+#define DEFINE_TEST_ALLOC(func, free_func, want_arg, want_gfp, want_node)\
+static int __init test_ ## func (void *arg)				\
+{									\
+	volatile size_t a = TEST_SIZE;					\
+	volatile size_t b = (SIZE_MAX / TEST_SIZE) + 1;			\
+	void *ptr;							\
+									\
+	/* Tiny allocation test. */					\
+	ptr = alloc ## want_arg ## want_gfp ## want_node (func, arg, 1);\
+	if (!ptr) {							\
+		pr_warn(#func " failed regular allocation?!\n");	\
+		return 1;						\
+	}								\
+	free ## want_arg (free_func, arg, ptr);				\
+									\
+	/* Wrapped allocation test. */					\
+	ptr = alloc ## want_arg ## want_gfp ## want_node (func, arg,	\
+							  a * b);	\
+	if (!ptr) {							\
+		pr_warn(#func " unexpectedly failed bad wrapping?!\n");	\
+		return 1;						\
+	}								\
+	free ## want_arg (free_func, arg, ptr);				\
+									\
+	/* Saturated allocation test. */				\
+	ptr = alloc ## want_arg ## want_gfp ## want_node (func, arg,	\
+						   array_size(a, b));	\
+	if (ptr) {							\
+		pr_warn(#func " missed saturation!\n");			\
+		free ## want_arg (free_func, arg, ptr);			\
+		return 1;						\
+	}								\
+	pr_info(#func " detected saturation\n");			\
+	return 0;							\
+}
+
+/*
+ * Allocator uses a trailing node argument --------+  (e.g. kmalloc_node())
+ * Allocator uses the gfp_t argument -----------+  |  (e.g. kmalloc())
+ * Allocator uses a special leading argument +  |  |  (e.g. devm_kmalloc())
+ *                                           |  |  |
+ */
+DEFINE_TEST_ALLOC(kmalloc,	 kfree,	     0, 1, 0);
+DEFINE_TEST_ALLOC(kmalloc_node,	 kfree,	     0, 1, 1);
+DEFINE_TEST_ALLOC(kzalloc,	 kfree,	     0, 1, 0);
+DEFINE_TEST_ALLOC(kzalloc_node,  kfree,	     0, 1, 1);
+DEFINE_TEST_ALLOC(vmalloc,	 vfree,	     0, 0, 0);
+DEFINE_TEST_ALLOC(vmalloc_node,  vfree,	     0, 0, 1);
+DEFINE_TEST_ALLOC(vzalloc,	 vfree,	     0, 0, 0);
+DEFINE_TEST_ALLOC(vzalloc_node,  vfree,	     0, 0, 1);
+DEFINE_TEST_ALLOC(kvmalloc,	 kvfree,     0, 1, 0);
+DEFINE_TEST_ALLOC(kvmalloc_node, kvfree,     0, 1, 1);
+DEFINE_TEST_ALLOC(kvzalloc,	 kvfree,     0, 1, 0);
+DEFINE_TEST_ALLOC(kvzalloc_node, kvfree,     0, 1, 1);
+DEFINE_TEST_ALLOC(devm_kmalloc,  devm_kfree, 1, 1, 0);
+DEFINE_TEST_ALLOC(devm_kzalloc,  devm_kfree, 1, 1, 0);
+
+static int __init test_overflow_allocation(void)
+{
+	const char device_name[] = "overflow-test";
+	struct device *dev;
+	int err = 0;
+
+	/* Create dummy device for devm_kmalloc()-family tests. */
+	dev = root_device_register(device_name);
+	if (!dev) {
+		pr_warn("Cannot register test device\n");
+		return 1;
+	}
+
+	err |= test_kmalloc(NULL);
+	err |= test_kmalloc_node(NULL);
+	err |= test_kzalloc(NULL);
+	err |= test_kzalloc_node(NULL);
+	err |= test_kvmalloc(NULL);
+	err |= test_kvmalloc_node(NULL);
+	err |= test_kvzalloc(NULL);
+	err |= test_kvzalloc_node(NULL);
+	err |= test_vmalloc(NULL);
+	err |= test_vmalloc_node(NULL);
+	err |= test_vzalloc(NULL);
+	err |= test_vzalloc_node(NULL);
+	err |= test_devm_kmalloc(dev);
+	err |= test_devm_kzalloc(dev);
+
+	device_unregister(dev);
+
+	return err;
+}
+
+static int __init test_module_init(void)
+{
+	int err = 0;
+
+	err |= test_overflow_calculation();
+	err |= test_overflow_allocation();
+
+	if (err) {
+		pr_warn("FAIL!\n");
+		err = -EINVAL;
+	} else {
+		pr_info("all tests passed\n");
+	}
+
+	return err;
+}
+
+static void __exit test_module_exit(void)
+{ }
+
+module_init(test_module_init);
+module_exit(test_module_exit);
+MODULE_LICENSE("Dual MIT/GPL");

net/ceph/mon_client.c

···
 
 	if (num_mon > CEPH_MAX_MON)
 		goto bad;
-	m = kmalloc(sizeof(*m) + sizeof(m->mon_inst[0])*num_mon, GFP_NOFS);
+	m = kmalloc(struct_size(m, mon_inst, num_mon), GFP_NOFS);
 	if (m == NULL)
 		return ERR_PTR(-ENOMEM);
 	m->fsid = fsid;
···
 	int i;
 
 	/* build initial monmap */
-	monc->monmap = kzalloc(sizeof(*monc->monmap) +
-			       num_mon*sizeof(monc->monmap->mon_inst[0]),
+	monc->monmap = kzalloc(struct_size(monc->monmap, mon_inst, num_mon),
 			       GFP_KERNEL);
 	if (!monc->monmap)
 		return -ENOMEM;

net/ceph/osd_client.c

···
 		req = kmem_cache_alloc(ceph_osd_request_cache, gfp_flags);
 	} else {
 		BUG_ON(num_ops > CEPH_OSD_MAX_OPS);
-		req = kmalloc(sizeof(*req) + num_ops * sizeof(req->r_ops[0]),
-			      gfp_flags);
+		req = kmalloc(struct_size(req, r_ops, num_ops), gfp_flags);
 	}
 	if (unlikely(!req))
 		return NULL;

net/netfilter/xt_recent.c

···
 	}
 
 	nstamps_max += 1;
-	e = kmalloc(sizeof(*e) + sizeof(e->stamps[0]) * nstamps_max,
-		    GFP_ATOMIC);
+	e = kmalloc(struct_size(e, stamps, nstamps_max), GFP_ATOMIC);
 	if (e == NULL)
 		return NULL;
 	memcpy(&e->addr, addr, sizeof(e->addr));

net/sctp/endpointola.c

···
 		 * variables.  There are arrays that we encode directly
 		 * into parameters to make the rest of the operations easier.
 		 */
-		auth_hmacs = kzalloc(sizeof(*auth_hmacs) +
-				     sizeof(__u16) * SCTP_AUTH_NUM_HMACS, gfp);
+		auth_hmacs = kzalloc(struct_size(auth_hmacs, hmac_ids,
+						 SCTP_AUTH_NUM_HMACS), gfp);
 		if (!auth_hmacs)
 			goto nomem;
 

sound/core/vmaster.c

···
 	struct link_master *master_link = snd_kcontrol_chip(master);
 	struct link_slave *srec;
 
-	srec = kzalloc(sizeof(*srec) +
-		       slave->count * sizeof(*slave->vd), GFP_KERNEL);
+	srec = kzalloc(struct_size(srec, slave.vd, slave->count),
+		       GFP_KERNEL);
 	if (!srec)
 		return -ENOMEM;
 	srec->kctl = slave;

sound/soc/qcom/apq8016_sbc.c

···
 	num_links = of_get_child_count(node);
 
 	/* Allocate the private data and the DAI link array */
-	data = devm_kzalloc(dev, sizeof(*data) + sizeof(*link) * num_links,
+	data = devm_kzalloc(dev,
+			    struct_size(data, dai_link, num_links),
 			    GFP_KERNEL);
 	if (!data)
 		return ERR_PTR(-ENOMEM);

sound/soc/soc-dapm.c

···
 	list_for_each(it, widgets)
 		size++;
 
-	*list = kzalloc(sizeof(**list) + size * sizeof(*w), GFP_KERNEL);
+	*list = kzalloc(struct_size(*list, widgets, size), GFP_KERNEL);
 	if (*list == NULL)
 		return -ENOMEM;