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Subject[PATCH] block: Fix wrong offset in bio_truncate()
Date
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@syzkaller.appspotmail.com
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---
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@mail.parknet.co.jp>

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