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From:   Ryusuke Konishi <konishi.ryusuke@gmail.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-nilfs <linux-nilfs@vger.kernel.org>,
        syzbot <syzbot+2b32eb36c1a825b7a74c@syzkaller.appspotmail.com>,
        syzkaller-bugs@googlegroups.com,
        LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] nilfs2: fix NULL pointer dereference at nilfs_bmap_lookup_at_level()
Date:   Sun,  2 Oct 2022 12:08:04 +0900
Message-Id: <20221002030804.29978-1-konishi.ryusuke@gmail.com>
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References: <000000000000eb0ba805e9d6e30e@google.com>
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If the i_mode field in inode of metadata files is corrupted on disk,
it can cause the initialization of bmap structure, which should have
been called from nilfs_read_inode_common(), not to be called.  This
causes a lockdep warning followed by a NULL pointer dereference at
nilfs_bmap_lookup_at_level().

This patch fixes these issues by adding a missing sanitiy check for
the i_mode field of metadata file's inode.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+2b32eb36c1a825b7a74c@syzkaller.appspotmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: stable@vger.kernel.org
---
 fs/nilfs2/inode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 67f63cfeade5..d4e653d51869 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -440,6 +440,8 @@ int nilfs_read_inode_common(struct inode *inode,
 	inode->i_atime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
 	inode->i_ctime.tv_nsec = le32_to_cpu(raw_inode->i_ctime_nsec);
 	inode->i_mtime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
+	if (nilfs_is_metadata_file_inode(inode) && !S_ISREG(inode->i_mode))
+		return -EIO; /* this inode is for metadata and corrupted */
 	if (inode->i_nlink == 0)
 		return -ESTALE; /* this inode is deleted */
 
-- 
2.34.1