linux-kernel - [PATCH AUTOSEL 5.4 8/8] block: Fix wrong offset in bio

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Date:   Sat, 22 Jan 2022 19:13:23 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        syzbot+ac94ae5f68b84197f41c@...kaller.appspotmail.com,
        Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>, linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 8/8] block: Fix wrong offset in bio_truncate()

From: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>

[ 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@...kaller.appspotmail.com
Signed-off-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Reviewed-by: Ming Lei <ming.lei@...hat.com>
Link: https://lore.kernel.org/r/875yqt1c9g.fsf@mail.parknet.co.jp
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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