Re: [syzbot] general protection fault in prt_str

[syzbot <syzbot+37186860aa7812b331d5@syzkaller.appspotmail.com>]

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***

Subject: general protection fault in prt_str
Author: djahchankoike@gmail.com

#syz test

syzbot reported a null ptr deref when printing mount options [1].

This happens because syzbot can pass options such as ',appraise,'
with no value associated with it, since it is a unknown option and
is not in the 'noopt' form it does not check for null values.
Change so that unknown options with invalid values are reported.

Signed-off-by: Diogo Jahchan Koike <djahchankoike@gmail.com>
---
 fs/bcachefs/opts.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/bcachefs/opts.c b/fs/bcachefs/opts.c
index e10fc1da71b1..1ccaed5c340b 100644
--- a/fs/bcachefs/opts.c
+++ b/fs/bcachefs/opts.c
@@ -482,6 +482,10 @@ int bch2_parse_one_mount_opt(struct bch_fs *c, struct bch_opts *opts,
 		val = "0";
 	}
 
+	/* Unknown options with invalid values are reported */
+	if (id < 0 && !val)
+		goto bad_val;
+
 	/* Unknown options are ignored: */
 	if (id < 0)
 		return 0;
-- 
2.43.0