From: Immad Mir <mirimmad17@xxxxxxxxx> [ Upstream commit 47cfdc338d674d38f4b2f22b7612cc6a2763ba27 ] Syzkaller reported an issue where txBegin may be called on a superblock in a read-only mounted filesystem which leads to NULL pointer deref. This could be solved by checking if the filesystem is read-only before calling txBegin, and returning with appropiate error code. Reported-By: syzbot+f1faa20eec55e0c8644c@xxxxxxxxxxxxxxxxxxxxxxxxx Link: https://syzkaller.appspot.com/bug?id=be7e52c50c5182cc09a09ea6fc456446b2039de3 Signed-off-by: Immad Mir <mirimmad17@xxxxxxxxx> Signed-off-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/jfs/namei.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c index 4fbbf88435e69..b3a0fe0649c49 100644 --- a/fs/jfs/namei.c +++ b/fs/jfs/namei.c @@ -799,6 +799,11 @@ static int jfs_link(struct dentry *old_dentry, if (rc) goto out; + if (isReadOnly(ip)) { + jfs_error(ip->i_sb, "read-only filesystem\n"); + return -EROFS; + } + tid = txBegin(ip->i_sb, 0); mutex_lock_nested(&JFS_IP(dir)->commit_mutex, COMMIT_MUTEX_PARENT); -- 2.39.2
