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From:   Alexander Potapenko <glider@google.com>
Date:   Fri, 11 Oct 2019 13:51:37 +0200
Message-ID: <CAG_fn=WsN0d8VO6=4jtDP9rHqBMp0zBvJQ7qrvQhZkkaj6NNsg@mail.gmail.com>
Subject: Re: KMSAN: uninit-value in alauda_check_media
To:     Jaskaran Singh <jaskaransingh7654321@gmail.com>
Cc:     syzbot <syzbot+e7d46eb426883fb97efd@syzkaller.appspotmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        usb-storage@lists.one-eyed-alien.net
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Sender: linux-kernel-owner@vger.kernel.org
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On Fri, Oct 11, 2019 at 1:23 PM Jaskaran Singh
<jaskaransingh7654321@gmail.com> wrote:
>
> On Mon, 2019-10-07 at 12:39 -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    1e76a3e5 kmsan: replace __GFP_NO_KMSAN_SHADOW with
> > kmsan_i..
> > git tree:       https://github.com/google/kmsan.git master
> > console output:
> > https://syzkaller.appspot.com/x/log.txt?x=3D1204cc63600000
> > kernel config:
> > https://syzkaller.appspot.com/x/.config?x=3Df03c659d0830ab8d
> > dashboard link:
> > https://syzkaller.appspot.com/bug?extid=3De7d46eb426883fb97efd
> > compiler:       clang version 9.0.0 (/home/glider/llvm/clang
> > 80fee25776c2fb61e74c1ecb1a523375c2500b69)
> > syz repro:
> > https://syzkaller.appspot.com/x/repro.syz?x=3D123c860d600000
> > C reproducer:
> > https://syzkaller.appspot.com/x/repro.c?x=3D110631b7600000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the
> > commit:
> > Reported-by: syzbot+e7d46eb426883fb97efd@syzkaller.appspotmail.com
> >
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
> > BUG: KMSAN: uninit-value in alauda_transport+0x462/0x57f0
> > drivers/usb/storage/alauda.c:1137
> > CPU: 0 PID: 12279 Comm: usb-storage Not tainted 5.3.0-rc7+ #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine,
> > BIOS
> > Google 01/01/2011
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0x191/0x1f0 lib/dump_stack.c:113
> >   kmsan_report+0x13a/0x2b0 mm/kmsan/kmsan_report.c:108
> >   __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
> >   alauda_check_media+0x344/0x3310 drivers/usb/storage/alauda.c:460
> >   alauda_transport+0x462/0x57f0 drivers/usb/storage/alauda.c:1137
> >   usb_stor_invoke_transport+0xf5/0x27e0
> > drivers/usb/storage/transport.c:606
> >   usb_stor_transparent_scsi_command+0x5d/0x70
> > drivers/usb/storage/protocol.c:108
> >   usb_stor_control_thread+0xca6/0x11a0 drivers/usb/storage/usb.c:380
> >   kthread+0x4b5/0x4f0 kernel/kthread.c:256
> >   ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
> >
> > Local variable description: ----status@alauda_check_media
> > Variable was created at:
> >   alauda_check_media+0x8e/0x3310 drivers/usb/storage/alauda.c:454
> >   alauda_transport+0x462/0x57f0 drivers/usb/storage/alauda.c:1137
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
> > Kernel panic - not syncing: panic_on_warn set ...
> > CPU: 0 PID: 12279 Comm: usb-storage Tainted:
> > G    B             5.3.0-rc7+
> > #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine,
> > BIOS
> > Google 01/01/2011
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0x191/0x1f0 lib/dump_stack.c:113
> >   panic+0x3c9/0xc1e kernel/panic.c:219
> >   kmsan_report+0x2a2/0x2b0 mm/kmsan/kmsan_report.c:131
> >   __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
> >   alauda_check_media+0x344/0x3310 drivers/usb/storage/alauda.c:460
> >   alauda_transport+0x462/0x57f0 drivers/usb/storage/alauda.c:1137
> >   usb_stor_invoke_transport+0xf5/0x27e0
> > drivers/usb/storage/transport.c:606
> >   usb_stor_transparent_scsi_command+0x5d/0x70
> > drivers/usb/storage/protocol.c:108
> >   usb_stor_control_thread+0xca6/0x11a0 drivers/usb/storage/usb.c:380
> >   kthread+0x4b5/0x4f0 kernel/kthread.c:256
> >   ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
> > Kernel Offset: disabled
> > Rebooting in 86400 seconds..
> >
> >
> > ---
> > This bug is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this bug report. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > syzbot can test patches for this bug, for details see:
> > https://goo.gl/tpsmEJ#testing-patches
>
> #syz test: https://github.com/google/kmsan.git 1e76a3e5
This didn't work, let's try with the master:
#syz test: https://github.com/google/kmsan.git master

>
> diff --git a/drivers/usb/storage/alauda.c
> b/drivers/usb/storage/alauda.c
> index ddab2cd3d2e7..bb309b9ad65b 100644
> --- a/drivers/usb/storage/alauda.c
> +++ b/drivers/usb/storage/alauda.c
> @@ -452,7 +452,7 @@ static int alauda_init_media(struct us_data *us)
>  static int alauda_check_media(struct us_data *us)
>  {
>         struct alauda_info *info =3D (struct alauda_info *) us->extra;
> -       unsigned char status[2];
> +       unsigned char *status =3D us->iobuf;
>         int rc;
>
>         rc =3D alauda_get_media_status(us, status);
>
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--=20
Alexander Potapenko
Software Engineer

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