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> --- block/bio.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block/bio.c b/block/bio.c index a6fb6a0..25f1ed2 100644 --- a/block/bio.c 2021-11-01 09:19:05.999472589 +0900 +++ b/block/bio.c 2022-01-09 17:40:09.010438012 +0900 @@ -567,7 +567,8 @@ void bio_truncate(struct bio *bio, unsig 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; _ -- OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
