From 3ee859e384d453d6ac68bfd5971f630d9fa46ad3 Mon Sep 17 00:00:00 2001
From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Date: Sun, 9 Jan 2022 18:36:43 +0900
Subject: [PATCH] block: Fix wrong offset in bio_truncate()
Git-commit: 3ee859e384d453d6ac68bfd5971f630d9fa46ad3
Patch-mainline: v5.17-rc1
References: git-fixes

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>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/875yqt1c9g.fsf@mail.parknet.co.jp
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Coly Li <colyli@suse.de>

---
 block/bio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 0d400ba2dbd1..4312a8085396 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -569,7 +569,8 @@ static 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;
-- 
2.35.3