[PATCH] block: fix integer overflow in BLKSECDISCARD

[Alexey Dobriyan <adobriyan@xxxxxxxxx>]

I independently rediscovered

	commit 22d24a544b0d49bbcbd61c8c0eaf77d3c9297155
	block: fix overflow in blk_ioctl_discard()

but for secure erase.

Same problem:

	uint64_t r[2] = {512, 18446744073709551104ULL};
	ioctl(fd, BLKSECDISCARD, r);

will enter near infinite loop inside blkdev_issue_secure_erase():

	a.out: attempt to access beyond end of device
	loop0: rw=5, sector=3399043073, nr_sectors = 1024 limit=2048
	bio_check_eod: 3286214 callbacks suppressed

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---

 block/ioctl.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -126,7 +126,7 @@ static int blk_ioctl_discard(struct block_device *bdev, blk_mode_t mode,
 		return -EINVAL;
 
 	filemap_invalidate_lock(bdev->bd_mapping);
-	err = truncate_bdev_range(bdev, mode, start, start + len - 1);
+	err = truncate_bdev_range(bdev, mode, start, end - 1);
 	if (err)
 		goto fail;
 
@@ -163,7 +163,7 @@ static int blk_ioctl_discard(struct block_device *bdev, blk_mode_t mode,
 static int blk_ioctl_secure_erase(struct block_device *bdev, blk_mode_t mode,
 		void __user *argp)
 {
-	uint64_t start, len;
+	uint64_t start, len, end;
 	uint64_t range[2];
 	int err;
 
@@ -178,11 +178,12 @@ static int blk_ioctl_secure_erase(struct block_device *bdev, blk_mode_t mode,
 	len = range[1];
 	if ((start & 511) || (len & 511))
 		return -EINVAL;
-	if (start + len > bdev_nr_bytes(bdev))
+	if (check_add_overflow(start, len, &end) ||
+	    end > bdev_nr_bytes(bdev))
 		return -EINVAL;
 
 	filemap_invalidate_lock(bdev->bd_mapping);
-	err = truncate_bdev_range(bdev, mode, start, start + len - 1);
+	err = truncate_bdev_range(bdev, mode, start, end - 1);
 	if (!err)
 		err = blkdev_issue_secure_erase(bdev, start >> 9, len >> 9,
 						GFP_KERNEL);