[PATCH AUTOSEL 5.4 8/8] block: Fix wrong offset in bio_truncate()

[Sasha Levin]

From: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>

[ Upstream commit 3ee859e384d453d6ac68bfd5971f630d9fa46ad3 ]

bio_truncate() clears the buffer outside of last block of bdev, however
current bio_truncate() is using the wrong offset of page. So it can
return the uninitialized data.

This happened when both of truncated/corrupted FS and userspace (via
bdev) are trying to read the last of bdev.

Reported-by: syzbot+ac94ae5f68b84197f41c@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Link: https://lore.kernel.org/r/875yqt1c9g.fsf@xxxxxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 block/bio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index cb38d6f3acceb..1c52d0196e15c 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -569,7 +569,8 @@ void bio_truncate(struct bio *bio, unsigned new_size)
 				offset = new_size - done;
 			else
 				offset = 0;
-			zero_user(bv.bv_page, offset, bv.bv_len - offset);
+			zero_user(bv.bv_page, bv.bv_offset + offset,
+				  bv.bv_len - offset);
 			truncated = true;
 		}
 		done += bv.bv_len;
-- 
2.34.1