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From:   Alexander Potapenko <glider@google.com>
Date:   Thu, 14 Sep 2023 18:06:01 +0200
Message-ID: <CAG_fn=Umt5Gm1aFa2Tr8LCXboDZvBx9WBw_AvvkN3_7eyXSsRg@mail.gmail.com>
Subject: Re: [syzbot] [sctp?] [reiserfs?] KMSAN: uninit-value in __schedule (4)
To:     Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc:     syzbot <syzbot+00f1a932d27258b183e7@syzkaller.appspotmail.com>,
        bp@alien8.de, brauner@kernel.org, dave.hansen@linux.intel.com,
        hpa@zytor.com, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-sctp@vger.kernel.org,
        lucien.xin@gmail.com, mingo@redhat.com, netdev@vger.kernel.org,
        reiserfs-devel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        tglx@linutronix.de, x86@kernel.org
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On Thu, Sep 14, 2023 at 5:25=E2=80=AFPM Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
>
> On Tue, Sep 05, 2023 at 10:55:01AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    a47fc304d2b6 Add linux-next specific files for 20230831
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=3D131da298680=
000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=3D6ecd2a74f20=
953b9
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3D00f1a932d2725=
8b183e7
> > compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for=
 Debian) 2.40
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=3D116e5fcba=
80000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D118e912fa80=
000
>
> Not sure why sctp got tagged here. I could not find anything network
> related on this reproducer or console output.

I am afraid this is the effect of reports from different tools being
clustered together: https://github.com/google/syzkaller/issues/4168
The relevant KMSAN report can be viewed on the dashboard:
https://syzkaller.appspot.com/text?tag=3DCrashReport&x=3D144ba287a80000 -
that's where sctp was deduced from.

I suspect there's still nothing specific to sctp though: looks like
schedule_debug() somehow accidentally reads past the end of the task
stack.

>   Marcelo
>
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--=20
Alexander Potapenko
Software Engineer

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