treewide: Change list_sort to use const pointers

list_sort() internally casts the comparison function passed to it
to a different type with constant struct list_head pointers, and
uses this pointer to call the functions, which trips indirect call
Control-Flow Integrity (CFI) checking.

Instead of removing the consts, this change defines the
list_cmp_func_t type and changes the comparison function types of
all list_sort() callers to use const pointers, thus avoiding type
mismatches.

Suggested-by: Nick Desaulniers <[e-mail]>
Signed-off-by: Sami Tolvanen <[e-mail]>
Reviewed-by: Nick Desaulniers <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Tested-by: Nick Desaulniers <[e-mail]>
Tested-by: Nathan Chancellor <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm64/kvm/vgic/vgic-its.c

···
 	return offset;
 }
 
-static int vgic_its_ite_cmp(void *priv, struct list_head *a,
-			    struct list_head *b)
+static int vgic_its_ite_cmp(void *priv, const struct list_head *a,
+			    const struct list_head *b)
 {
 	struct its_ite *itea = container_of(a, struct its_ite, ite_list);
 	struct its_ite *iteb = container_of(b, struct its_ite, ite_list);
···
 	return offset;
 }
 
-static int vgic_its_device_cmp(void *priv, struct list_head *a,
-			       struct list_head *b)
+static int vgic_its_device_cmp(void *priv, const struct list_head *a,
+			       const struct list_head *b)
 {
 	struct its_device *deva = container_of(a, struct its_device, dev_list);
 	struct its_device *devb = container_of(b, struct its_device, dev_list);

arch/arm64/kvm/vgic/vgic.c

···
  * Return negative if "a" sorts before "b", 0 to preserve order, and positive
  * to sort "b" before "a".
  */
-static int vgic_irq_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int vgic_irq_cmp(void *priv, const struct list_head *a,
+			const struct list_head *b)
 {
 	struct vgic_irq *irqa = container_of(a, struct vgic_irq, ap_list);
 	struct vgic_irq *irqb = container_of(b, struct vgic_irq, ap_list);

block/blk-mq-sched.c

···
 	blk_mq_run_hw_queue(hctx, true);
 }
 
-static int sched_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int sched_rq_cmp(void *priv, const struct list_head *a,
+			const struct list_head *b)
 {
 	struct request *rqa = container_of(a, struct request, queuelist);
 	struct request *rqb = container_of(b, struct request, queuelist);

block/blk-mq.c

···
 	spin_unlock(&ctx->lock);
 }
 
-static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int plug_rq_cmp(void *priv, const struct list_head *a,
+		       const struct list_head *b)
 {
 	struct request *rqa = container_of(a, struct request, queuelist);
 	struct request *rqb = container_of(b, struct request, queuelist);

drivers/acpi/nfit/core.c

···
 	return 0;
 }
 
-static int nfit_mem_cmp(void *priv, struct list_head *_a, struct list_head *_b)
+static int nfit_mem_cmp(void *priv, const struct list_head *_a,
+		const struct list_head *_b)
 {
 	struct nfit_mem *a = container_of(_a, typeof(*a), list);
 	struct nfit_mem *b = container_of(_b, typeof(*b), list);

drivers/acpi/numa/hmat.c

···
 	return updated;
 }
 
-static int initiator_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int initiator_cmp(void *priv, const struct list_head *a,
+			 const struct list_head *b)
 {
 	struct memory_initiator *ia;
 	struct memory_initiator *ib;

drivers/clk/keystone/sci-clk.c

···
 
 #else
 
-static int _cmp_sci_clk_list(void *priv, struct list_head *a,
-			     struct list_head *b)
+static int _cmp_sci_clk_list(void *priv, const struct list_head *a,
+			     const struct list_head *b)
 {
 	struct sci_clk *ca = container_of(a, struct sci_clk, node);
 	struct sci_clk *cb = container_of(b, struct sci_clk, node);

drivers/gpu/drm/drm_modes.c

···
  * Negative if @lh_a is better than @lh_b, zero if they're equivalent, or
  * positive if @lh_b is better than @lh_a.
  */
-static int drm_mode_compare(void *priv, struct list_head *lh_a, struct list_head *lh_b)
+static int drm_mode_compare(void *priv, const struct list_head *lh_a,
+			    const struct list_head *lh_b)
 {
 	struct drm_display_mode *a = list_entry(lh_a, struct drm_display_mode, head);
 	struct drm_display_mode *b = list_entry(lh_b, struct drm_display_mode, head);

drivers/gpu/drm/i915/gt/intel_engine_user.c

···
 	[VIDEO_ENHANCEMENT_CLASS] = I915_ENGINE_CLASS_VIDEO_ENHANCE,
 };
 
-static int engine_cmp(void *priv, struct list_head *A, struct list_head *B)
+static int engine_cmp(void *priv, const struct list_head *A,
+		      const struct list_head *B)
 {
 	const struct intel_engine_cs *a =
 		container_of((struct rb_node *)A, typeof(*a), uabi_node);

drivers/gpu/drm/i915/gvt/debugfs.c

···
 
 /* Compare two diff_mmio items. */
 static int mmio_offset_compare(void *priv,
-	struct list_head *a, struct list_head *b)
+	const struct list_head *a, const struct list_head *b)
 {
 	struct diff_mmio *ma;
 	struct diff_mmio *mb;

drivers/gpu/drm/i915/selftests/i915_gem_gtt.c

···
 	return exercise_ppgtt(arg, shrink_boom);
 }
 
-static int sort_holes(void *priv, struct list_head *A, struct list_head *B)
+static int sort_holes(void *priv, const struct list_head *A,
+		      const struct list_head *B)
 {
 	struct drm_mm_node *a = list_entry(A, typeof(*a), hole_stack);
 	struct drm_mm_node *b = list_entry(B, typeof(*b), hole_stack);

drivers/gpu/drm/radeon/radeon_cs.c

···
 	return 0;
 }
 
-static int cmp_size_smaller_first(void *priv, struct list_head *a,
-				  struct list_head *b)
+static int cmp_size_smaller_first(void *priv, const struct list_head *a,
+				  const struct list_head *b)
 {
 	struct radeon_bo_list *la = list_entry(a, struct radeon_bo_list, tv.head);
 	struct radeon_bo_list *lb = list_entry(b, struct radeon_bo_list, tv.head);

drivers/infiniband/hw/usnic/usnic_uiom_interval_tree.c

···
 	return interval;
 }
 
-static int interval_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int interval_cmp(void *priv, const struct list_head *a,
+			const struct list_head *b)
 {
 	struct usnic_uiom_interval_node *node_a, *node_b;
 

drivers/interconnect/qcom/bcm-voter.c

···
 	u32 tcs_wait;
 };
 
-static int cmp_vcd(void *priv, struct list_head *a, struct list_head *b)
+static int cmp_vcd(void *priv, const struct list_head *a, const struct list_head *b)
 {
 	const struct qcom_icc_bcm *bcm_a = list_entry(a, struct qcom_icc_bcm, list);
 	const struct qcom_icc_bcm *bcm_b = list_entry(b, struct qcom_icc_bcm, list);

drivers/md/raid5.c

···
 		submit_bio_noacct(bio);
 }
 
-static int cmp_stripe(void *priv, struct list_head *a, struct list_head *b)
+static int cmp_stripe(void *priv, const struct list_head *a,
+		      const struct list_head *b)
 {
 	const struct r5pending_data *da = list_entry(a,
 				struct r5pending_data, sibling);

drivers/misc/sram.c

···
 	}
 }
 
-static int sram_reserve_cmp(void *priv, struct list_head *a,
-					struct list_head *b)
+static int sram_reserve_cmp(void *priv, const struct list_head *a,
+					const struct list_head *b)
 {
 	struct sram_reserve *ra = list_entry(a, struct sram_reserve, list);
 	struct sram_reserve *rb = list_entry(b, struct sram_reserve, list);

drivers/nvme/host/core.c

···
 	return ret;
 }
 
-static int ns_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int ns_cmp(void *priv, const struct list_head *a,
+		const struct list_head *b)
 {
 	struct nvme_ns *nsa = container_of(a, struct nvme_ns, list);
 	struct nvme_ns *nsb = container_of(b, struct nvme_ns, list);

drivers/pci/controller/cadence/pcie-cadence-host.c

···
 	return 0;
 }
 
-static int cdns_pcie_host_dma_ranges_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int cdns_pcie_host_dma_ranges_cmp(void *priv, const struct list_head *a,
+					 const struct list_head *b)
 {
 	struct resource_entry *entry1, *entry2;
 

drivers/spi/spi-loopback-test.c

···
 	u8 *end;
 };
 
-static int rx_ranges_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int rx_ranges_cmp(void *priv, const struct list_head *a,
+			 const struct list_head *b)
 {
 	struct rx_ranges *rx_a = list_entry(a, struct rx_ranges, list);
 	struct rx_ranges *rx_b = list_entry(b, struct rx_ranges, list);

fs/btrfs/raid56.c

···
 /*
  * rbios on the plug list are sorted for easier merging.
  */
-static int plug_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int plug_cmp(void *priv, const struct list_head *a,
+		    const struct list_head *b)
 {
 	struct btrfs_raid_bio *ra = container_of(a, struct btrfs_raid_bio,
 						 plug_list);

fs/btrfs/tree-log.c

···
 	return ret;
 }
 
-static int extent_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int extent_cmp(void *priv, const struct list_head *a,
+		      const struct list_head *b)
 {
 	struct extent_map *em1, *em2;
 

fs/btrfs/volumes.c

···
 	return 0;
 }
 
-static int devid_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int devid_cmp(void *priv, const struct list_head *a,
+		     const struct list_head *b)
 {
 	struct btrfs_device *dev1, *dev2;
 

fs/ext4/fsmap.c

···
 
 /* Compare two fsmap items. */
 static int ext4_getfsmap_compare(void *priv,
-				 struct list_head *a,
-				 struct list_head *b)
+				 const struct list_head *a,
+				 const struct list_head *b)
 {
 	struct ext4_fsmap *fa;
 	struct ext4_fsmap *fb;

fs/gfs2/glock.c

···
 	spin_unlock(&gl->gl_lockref.lock);
 }
 
-static int glock_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int glock_cmp(void *priv, const struct list_head *a,
+		     const struct list_head *b)
 {
 	struct gfs2_glock *gla, *glb;
 

fs/gfs2/log.c

···
 	}
 }
 
-static int ip_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int ip_cmp(void *priv, const struct list_head *a, const struct list_head *b)
 {
 	struct gfs2_inode *ipa, *ipb;
 

fs/gfs2/lops.c

···
 	kunmap_atomic(kaddr);
 }
 
-static int blocknr_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int blocknr_cmp(void *priv, const struct list_head *a,
+		       const struct list_head *b)
 {
 	struct gfs2_bufdata *bda, *bdb;
 

fs/iomap/buffered-io.c

···
 EXPORT_SYMBOL_GPL(iomap_ioend_try_merge);
 
 static int
-iomap_ioend_compare(void *priv, struct list_head *a, struct list_head *b)
+iomap_ioend_compare(void *priv, const struct list_head *a,
+		const struct list_head *b)
 {
 	struct iomap_ioend *ia = container_of(a, struct iomap_ioend, io_list);
 	struct iomap_ioend *ib = container_of(b, struct iomap_ioend, io_list);

fs/ubifs/gc.c

···
  * This function compares data nodes @a and @b. Returns %1 if @a has greater
  * inode or block number, and %-1 otherwise.
  */
-static int data_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
+static int data_nodes_cmp(void *priv, const struct list_head *a,
+			  const struct list_head *b)
 {
 	ino_t inuma, inumb;
 	struct ubifs_info *c = priv;
···
  * first and sorted by length in descending order. Directory entry nodes go
  * after inode nodes and are sorted in ascending hash valuer order.
  */
-static int nondata_nodes_cmp(void *priv, struct list_head *a,
-			     struct list_head *b)
+static int nondata_nodes_cmp(void *priv, const struct list_head *a,
+			     const struct list_head *b)
 {
 	ino_t inuma, inumb;
 	struct ubifs_info *c = priv;

fs/ubifs/replay.c

···
  * entries @a and @b by comparing their sequence numer.  Returns %1 if @a has
  * greater sequence number and %-1 otherwise.
  */
-static int replay_entries_cmp(void *priv, struct list_head *a,
-			      struct list_head *b)
+static int replay_entries_cmp(void *priv, const struct list_head *a,
+			      const struct list_head *b)
 {
 	struct ubifs_info *c = priv;
 	struct replay_entry *ra, *rb;

fs/xfs/scrub/bitmap.c

···
 static int
 xbitmap_range_cmp(
 	void			*priv,
-	struct list_head	*a,
-	struct list_head	*b)
+	const struct list_head	*a,
+	const struct list_head	*b)
 {
 	struct xbitmap_range	*ap;
 	struct xbitmap_range	*bp;

fs/xfs/xfs_bmap_item.c

···
 static int
 xfs_bmap_update_diff_items(
 	void				*priv,
-	struct list_head		*a,
-	struct list_head		*b)
+	const struct list_head		*a,
+	const struct list_head		*b)
 {
 	struct xfs_bmap_intent		*ba;
 	struct xfs_bmap_intent		*bb;

fs/xfs/xfs_buf.c

···
  */
 static int
 xfs_buf_cmp(
-	void		*priv,
-	struct list_head *a,
-	struct list_head *b)
+	void			*priv,
+	const struct list_head	*a,
+	const struct list_head	*b)
 {
 	struct xfs_buf	*ap = container_of(a, struct xfs_buf, b_list);
 	struct xfs_buf	*bp = container_of(b, struct xfs_buf, b_list);

fs/xfs/xfs_extent_busy.c

···
 int
 xfs_extent_busy_ag_cmp(
 	void			*priv,
-	struct list_head	*l1,
-	struct list_head	*l2)
+	const struct list_head	*l1,
+	const struct list_head	*l2)
 {
 	struct xfs_extent_busy	*b1 =
 		container_of(l1, struct xfs_extent_busy, list);

fs/xfs/xfs_extent_busy.h

···
 xfs_extent_busy_wait_all(struct xfs_mount *mp);
 
 int
-xfs_extent_busy_ag_cmp(void *priv, struct list_head *a, struct list_head *b);
+xfs_extent_busy_ag_cmp(void *priv, const struct list_head *a,
+	const struct list_head *b);
 
 static inline void xfs_extent_busy_sort(struct list_head *list)
 {

fs/xfs/xfs_extfree_item.c

···
 static int
 xfs_extent_free_diff_items(
 	void				*priv,
-	struct list_head		*a,
-	struct list_head		*b)
+	const struct list_head		*a,
+	const struct list_head		*b)
 {
 	struct xfs_mount		*mp = priv;
 	struct xfs_extent_free_item	*ra;

fs/xfs/xfs_refcount_item.c

···
 static int
 xfs_refcount_update_diff_items(
 	void				*priv,
-	struct list_head		*a,
-	struct list_head		*b)
+	const struct list_head		*a,
+	const struct list_head		*b)
 {
 	struct xfs_mount		*mp = priv;
 	struct xfs_refcount_intent	*ra;

fs/xfs/xfs_rmap_item.c

···
 static int
 xfs_rmap_update_diff_items(
 	void				*priv,
-	struct list_head		*a,
-	struct list_head		*b)
+	const struct list_head		*a,
+	const struct list_head		*b)
 {
 	struct xfs_mount		*mp = priv;
 	struct xfs_rmap_intent		*ra;

include/linux/list_sort.h

···
 
 struct list_head;
 
+typedef int __attribute__((nonnull(2,3))) (*list_cmp_func_t)(void *,
+		const struct list_head *, const struct list_head *);
+
 __attribute__((nonnull(2,3)))
-void list_sort(void *priv, struct list_head *head,
-	       int (*cmp)(void *priv, struct list_head *a,
-			  struct list_head *b));
+void list_sort(void *priv, struct list_head *head, list_cmp_func_t cmp);
 #endif

lib/list_sort.c

···
 #include <linux/list_sort.h>
 #include <linux/list.h>
 
-typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *,
-		struct list_head const *, struct list_head const *);
-
 /*
  * Returns a list organized in an intermediate format suited
  * to chaining of merge() calls: null-terminated, no reserved or
  * sentinel head node, "prev" links not maintained.
  */
 __attribute__((nonnull(2,3,4)))
-static struct list_head *merge(void *priv, cmp_func cmp,
+static struct list_head *merge(void *priv, list_cmp_func_t cmp,
 				struct list_head *a, struct list_head *b)
 {
 	struct list_head *head, **tail = &head;
···
  * throughout.
  */
 __attribute__((nonnull(2,3,4,5)))
-static void merge_final(void *priv, cmp_func cmp, struct list_head *head,
+static void merge_final(void *priv, list_cmp_func_t cmp, struct list_head *head,
 			struct list_head *a, struct list_head *b)
 {
 	struct list_head *tail = head;
···
  * 2^(k+1) - 1 (second merge of case 5 when x == 2^(k-1) - 1).
  */
 __attribute__((nonnull(2,3)))
-void list_sort(void *priv, struct list_head *head,
-		int (*cmp)(void *priv, struct list_head *a,
-			struct list_head *b))
+void list_sort(void *priv, struct list_head *head, list_cmp_func_t cmp)
 {
 	struct list_head *list = head->next, *pending = NULL;
 	size_t count = 0;	/* Count of pending */
···
 		if (likely(bits)) {
 			struct list_head *a = *tail, *b = a->prev;
 
-			a = merge(priv, (cmp_func)cmp, b, a);
+			a = merge(priv, cmp, b, a);
 			/* Install the merged result in place of the inputs */
 			a->prev = b->prev;
 			*tail = a;
···
 
 		if (!next)
 			break;
-		list = merge(priv, (cmp_func)cmp, pending, list);
+		list = merge(priv, cmp, pending, list);
 		pending = next;
 	}
 	/* The final merge, rebuilding prev links */
-	merge_final(priv, (cmp_func)cmp, head, pending, list);
+	merge_final(priv, cmp, head, pending, list);
 }
 EXPORT_SYMBOL(list_sort);

lib/test_list_sort.c

···
 	return 0;
 }
 
-static int __init cmp(void *priv, struct list_head *a, struct list_head *b)
+static int __init cmp(void *priv, const struct list_head *a,
+		      const struct list_head *b)
 {
 	struct debug_el *ela, *elb;
 

net/tipc/name_table.c

···
  * Code reused: time_after32() for the same purpose
  */
 #define publication_after(pa, pb) time_after32((pa)->id, (pb)->id)
-static int tipc_publ_sort(void *priv, struct list_head *a,
-			  struct list_head *b)
+static int tipc_publ_sort(void *priv, const struct list_head *a,
+			  const struct list_head *b)
 {
 	struct publication *pa, *pb;