linux-kernel - [PATCH] bfs: add check for return value of sb

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Message-ID: <tencent_9D1D4FB28DB4A59E0DBD9245DD84DDDC9907@qq.com>
Date: Sun,  3 Nov 2024 22:36:40 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+f51a2a34984e4d8888fd@...kaller.appspotmail.com
Cc: aivazian.tigran@...il.com,
	linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH] bfs: add check for return value of sb_getblk

Syzbot reported a null-ptr-deref in bfs_move_block.
sb_getblk() can fail, so need to check its return value.
If returned buffer head is not uptodate, it is considered corrupt.

Reported-and-tested-by: syzbot+f51a2a34984e4d8888fd@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f51a2a34984e4d8888fd
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 fs/bfs/file.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/bfs/file.c b/fs/bfs/file.c
index fa66a09e496a..983cc191d1e3 100644
--- a/fs/bfs/file.c
+++ b/fs/bfs/file.c
@@ -35,16 +35,28 @@ static int bfs_move_block(unsigned long from, unsigned long to,
 					struct super_block *sb)
 {
 	struct buffer_head *bh, *new;
+	int err = 0;
 
 	bh = sb_bread(sb, from);
 	if (!bh)
 		return -EIO;
 	new = sb_getblk(sb, to);
+	if (!new) {
+		bforget(bh);
+		return -ENOMEM;
+	}
+
+	if (!buffer_uptodate(new)) {
+		err = -EIO;
+		goto out;
+	}
+
 	memcpy(new->b_data, bh->b_data, bh->b_size);
 	mark_buffer_dirty(new);
+out:
 	bforget(bh);
 	brelse(new);
-	return 0;
+	return err;
 }
 
 static int bfs_move_blocks(struct super_block *sb, unsigned long start,
-- 
2.43.0