general protection fault in jffs2_parse_param

[syzbot]

syzbot suspects this issue was fixed by commit:

commit a61df3c413e49b0042f9caf774c58512d1cc71b7
Author: Jamie Iles <jamie at nuviainc.com>
Date:   Mon Oct 12 13:12:04 2020 +0000

    jffs2: Fix NULL pointer dereference in rp_size fs option parsing

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15cb91e7500000
start commit:   bf3e7628 Merge branch 'mtd/fixes' of git://git.kernel.org/..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=61033507391c77ff
dashboard link: https://syzkaller.appspot.com/bug?extid=9765367bb86a19d38732
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13d81f32500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13516852500000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: jffs2: Fix NULL pointer dereference in rp_size fs option parsing

For information about bisection process see: https://goo.gl/tpsmEJ#bisection