From 47cfdc338d674d38f4b2f22b7612cc6a2763ba27 Mon Sep 17 00:00:00 2001 From: Immad Mir Date: Fri, 23 Jun 2023 19:14:01 +0530 Subject: [PATCH] FS: JFS: Fix null-ptr-deref Read in txBegin 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@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=be7e52c50c5182cc09a09ea6fc456446b2039de3 Signed-off-by: Immad Mir Signed-off-by: Dave Kleikamp --- fs/jfs/namei.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c index b29d68b5eec5..f370c7605120 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);