vfio/platform: store mapped memory in region, instead of an on-stack copy

vfio_platform_{read,write}_mmio() call ioremap_nocache() to map
a region of io memory, which they store in struct vfio_platform_region to
be eventually re-used, or unmapped by vfio_platform_regions_cleanup().

These functions receive a copy of their struct vfio_platform_region
argument on the stack - so these mapped areas are always allocated, and
always leaked.

Pass this argument as a pointer instead.

Fixes: 6e3f26456009 "vfio/platform: read and write support for the device fd"
Signed-off-by: James Morse <[e-mail]>
Acked-by: Baptiste Reynal <[e-mail]>
Tested-by: Baptiste Reynal <[e-mail]>
Signed-off-by: Alex Williamson <[e-mail]>

drivers/vfio/platform/vfio_platform_common.c

···
 	return -ENOTTY;
 }
 
-static ssize_t vfio_platform_read_mmio(struct vfio_platform_region reg,
+static ssize_t vfio_platform_read_mmio(struct vfio_platform_region *reg,
 				       char __user *buf, size_t count,
 				       loff_t off)
 {
 	unsigned int done = 0;
 
-	if (!reg.ioaddr) {
-		reg.ioaddr =
-			ioremap_nocache(reg.addr, reg.size);
+	if (!reg->ioaddr) {
+		reg->ioaddr =
+			ioremap_nocache(reg->addr, reg->size);
 
-		if (!reg.ioaddr)
+		if (!reg->ioaddr)
 			return -ENOMEM;
 	}
 
···
 		if (count >= 4 && !(off % 4)) {
 			u32 val;
 
-			val = ioread32(reg.ioaddr + off);
+			val = ioread32(reg->ioaddr + off);
 			if (copy_to_user(buf, &val, 4))
 				goto err;
 
···
 		} else if (count >= 2 && !(off % 2)) {
 			u16 val;
 
-			val = ioread16(reg.ioaddr + off);
+			val = ioread16(reg->ioaddr + off);
 			if (copy_to_user(buf, &val, 2))
 				goto err;
 
···
 		} else {
 			u8 val;
 
-			val = ioread8(reg.ioaddr + off);
+			val = ioread8(reg->ioaddr + off);
 			if (copy_to_user(buf, &val, 1))
 				goto err;
 
···
 		return -EINVAL;
 
 	if (vdev->regions[index].type & VFIO_PLATFORM_REGION_TYPE_MMIO)
-		return vfio_platform_read_mmio(vdev->regions[index],
+		return vfio_platform_read_mmio(&vdev->regions[index],
 							buf, count, off);
 	else if (vdev->regions[index].type & VFIO_PLATFORM_REGION_TYPE_PIO)
 		return -EINVAL; /* not implemented */
···
 	return -EINVAL;
 }
 
-static ssize_t vfio_platform_write_mmio(struct vfio_platform_region reg,
+static ssize_t vfio_platform_write_mmio(struct vfio_platform_region *reg,
 					const char __user *buf, size_t count,
 					loff_t off)
 {
 	unsigned int done = 0;
 
-	if (!reg.ioaddr) {
-		reg.ioaddr =
-			ioremap_nocache(reg.addr, reg.size);
+	if (!reg->ioaddr) {
+		reg->ioaddr =
+			ioremap_nocache(reg->addr, reg->size);
 
-		if (!reg.ioaddr)
+		if (!reg->ioaddr)
 			return -ENOMEM;
 	}
 
···
 
 			if (copy_from_user(&val, buf, 4))
 				goto err;
-			iowrite32(val, reg.ioaddr + off);
+			iowrite32(val, reg->ioaddr + off);
 
 			filled = 4;
 		} else if (count >= 2 && !(off % 2)) {
···
 
 			if (copy_from_user(&val, buf, 2))
 				goto err;
-			iowrite16(val, reg.ioaddr + off);
+			iowrite16(val, reg->ioaddr + off);
 
 			filled = 2;
 		} else {
···
 
 			if (copy_from_user(&val, buf, 1))
 				goto err;
-			iowrite8(val, reg.ioaddr + off);
+			iowrite8(val, reg->ioaddr + off);
 
 			filled = 1;
 		}
···
 		return -EINVAL;
 
 	if (vdev->regions[index].type & VFIO_PLATFORM_REGION_TYPE_MMIO)
-		return vfio_platform_write_mmio(vdev->regions[index],
+		return vfio_platform_write_mmio(&vdev->regions[index],
 							buf, count, off);
 	else if (vdev->regions[index].type & VFIO_PLATFORM_REGION_TYPE_PIO)
 		return -EINVAL; /* not implemented */