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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Wed, 6 Nov 2019 16:36:45 +0100
Message-ID: <CACT4Y+a3WWKLPoLD7LC44gaDNQ-p13dW5FT4w1MatcL61u_+XQ@mail.gmail.com>
Subject: Re: WARNING in drm_mode_createblob_ioctl
To:     Daniel Vetter <daniel@ffwll.ch>
Cc:     syzbot <syzbot+fb77e97ebf0612ee6914@syzkaller.appspotmail.com>,
        Dave Airlie <airlied@linux.ie>,
        Andrew Morton <akpm@linux-foundation.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Kees Cook <keescook@chromium.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Sean Paul <sean@poorly.run>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Al Viro <viro@zeniv.linux.org.uk>
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On Wed, Nov 6, 2019 at 4:30 PM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Wed, Nov 6, 2019 at 4:20 PM syzbot
> <syzbot+fb77e97ebf0612ee6914@syzkaller.appspotmail.com> wrote:
> >
> > syzbot has bisected this bug to:
> >
> > commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
> > Author: Kees Cook <keescook@chromium.org>
> > Date:   Mon Nov 4 22:57:23 2019 +0000
> >
> >      uaccess: disallow > INT_MAX copy sizes
>
> Ah cool, this explains it.
>
> fwiw I never managed to get the WARNING in the backtrace to lign up
> with any code. No idea what's been going on.
>
> I'll type a patch to paper over this.
> -Daniel

If I get:
git checkout 8ada228a
then include/linux/thread_info.h:150
points right to:
if (WARN_ON_ONCE(bytes > INT_MAX))

Is the size user-controllable here?


> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=125fe6dce00000
> > start commit:   51309b9d Add linux-next specific files for 20191105
> > git tree:       linux-next
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=115fe6dce00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=165fe6dce00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=a9b1a641c1f1fc52
> > dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1212dc3ae00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=145f604ae00000
> >
> > Reported-by: syzbot+fb77e97ebf0612ee6914@syzkaller.appspotmail.com
> > Fixes: 9e5a64c71b2f ("uaccess: disallow > INT_MAX copy sizes")
> >
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>
> --
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