[PATCH V2] block: fix BLKSECDISCARD zero-length range causing page cache invalidation

From: Zizhi Wo <[email protected]>

Commit 697ba0b6ec4a ("block: fix integer overflow in BLKSECDISCARD") fixed
the start+len overflow via check_add_overflow() but did not handle the
start=0, len=0 case. There, start + len = 0, so end = 0 passes all checks,
and truncate_bdev_range()->truncate_inode_pages_range() is then called with
lend=UINT64_MAX, whitch is the "truncate to the end of file" sentinel, so
the entire page cache is invalidated.

Fix this by replacing the validation with blk_validate_byte_range(), which
already rejects a zero-length range and is what BLKDISCARD uses. This also
switches the alignment check from a hardcoded 512 to
bdev_logical_block_size().

Fixes: 0bd1ed4860d0 ("block: pass inclusive 'lend' parameter to truncate_inode_pages_range")
Signed-off-by: Zizhi Wo <[email protected]>
Reviewed-by: Yu Kuai <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
---
v2:
Add the fixtag.

v1: https://lore.kernel.org/all/[email protected]/
---
 block/ioctl.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index 3d4ea1537457..3b7d33a737e8 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -174,12 +174,11 @@ 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, end;
-	uint64_t range[2];
+	uint64_t range[2], start, len;
 	int err;
 
 	if (!(mode & BLK_OPEN_WRITE))
 		return -EBADF;
 	if (!bdev_max_secure_erase_sectors(bdev))
@@ -187,19 +186,17 @@ static int blk_ioctl_secure_erase(struct block_device *bdev, blk_mode_t mode,
 	if (copy_from_user(range, argp, sizeof(range)))
 		return -EFAULT;
 
 	start = range[0];
 	len = range[1];
-	if ((start & 511) || (len & 511))
-		return -EINVAL;
-	if (check_add_overflow(start, len, &end) ||
-	    end > bdev_nr_bytes(bdev))
-		return -EINVAL;
+	err = blk_validate_byte_range(bdev, start, len);
+	if (err)
+		return err;
 
 	inode_lock(bdev->bd_mapping->host);
 	filemap_invalidate_lock(bdev->bd_mapping);
-	err = truncate_bdev_range(bdev, mode, start, end - 1);
+	err = truncate_bdev_range(bdev, mode, start, start + len - 1);
 	if (!err)
 		err = blkdev_issue_secure_erase(bdev, start >> 9, len >> 9,
 						GFP_KERNEL);
 	filemap_invalidate_unlock(bdev->bd_mapping);
 	inode_unlock(bdev->bd_mapping->host);
-- 
2.52.0