linux-kernel - Re: [syzbot] [hfs?] kernel BUG in hfsplus_show

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Message-ID: <4F5F9CC2-803C-4E18-968C-A46B32528F1F@kernel.org>
Date:   Tue, 18 Jul 2023 21:18:05 -0700
From:   Kees Cook <kees@...nel.org>
To:     syzbot <syzbot+98d3ceb7e01269e7bf4f@...kaller.appspotmail.com>,
        andriy.shevchenko@...ux.intel.com, keescook@...omium.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [hfs?] kernel BUG in hfsplus_show_options

On July 18, 2023 6:27:23 PM PDT, syzbot <syzbot+98d3ceb7e01269e7bf4f@...kaller.appspotmail.com> wrote:
>syzbot has bisected this issue to:
>
>commit c30417b20f4993e49406f3f6d986355c6e943aa2
>Author: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
>Date:   Mon Jul 17 09:33:32 2023 +0000
>
>    seq_file: Replace strncpy()+nul by strscpy()

Uh... Wat. Is this a bug in strscpy fortification? It's copying out of a (recast) be32... It shouldn't expect to find a NUL because it hit the max copy size already...

Looking...

-Kees

>
>bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17488c1aa80000
>start commit:   aeba456828b4 Add linux-next specific files for 20230718
>git tree:       linux-next
>final oops:     https://syzkaller.appspot.com/x/report.txt?x=14c88c1aa80000
>console output: https://syzkaller.appspot.com/x/log.txt?x=10c88c1aa80000
>kernel config:  https://syzkaller.appspot.com/x/.config?x=e7ec534f91cfce6c
>dashboard link: https://syzkaller.appspot.com/bug?extid=98d3ceb7e01269e7bf4f
>syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15ecf646a80000
>C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1476f30aa80000
>
>Reported-by: syzbot+98d3ceb7e01269e7bf4f@...kaller.appspotmail.com
>Fixes: c30417b20f49 ("seq_file: Replace strncpy()+nul by strscpy()")
>
>For information about bisection process see: https://goo.gl/tpsmEJ#bisection


-- 
Kees Cook