[PATCH] bcachefs: Fix null-ptr-deref in bch2_opt_to_text

[Edward Adam Davis <eadavis@qq.com>]

The mounting option values passed in by syzbot are:
"metadata_checksum=crc64, errors=continue, obj_user={^, subj_user=obj_ur,
approve", which does not meet the "key1=value1,key2=value2,..." requirement
of the bcachefs.

Reported-and-tested-by: syzbot+294f528e56138c357a48@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=294f528e56138c357a48
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 fs/bcachefs/opts.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/bcachefs/opts.c b/fs/bcachefs/opts.c
index e10fc1da71b1..78307e092075 100644
--- a/fs/bcachefs/opts.c
+++ b/fs/bcachefs/opts.c
@@ -472,6 +472,12 @@ int bch2_parse_one_mount_opt(struct bch_fs *c, struct bch_opts *opts,
 	u64 v;
 	int ret, id;
 
+	if (!val) {
+		pr_err("Bad mount option, value is NULL");
+		ret = -BCH_ERR_option_value;
+		goto out;
+	}
+
 	id = bch2_mount_opt_lookup(name);
 
 	/* Check for the form "noopt", negation of a boolean opt: */
-- 
2.43.0