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From:   Daniel Vetter <daniel@ffwll.ch>
Date:   Wed, 6 Nov 2019 16:23:55 +0100
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Subject: Re: WARNING in drm_mode_createblob_ioctl
To:     syzbot <syzbot+fb77e97ebf0612ee6914@syzkaller.appspotmail.com>
Cc:     Dave Airlie <airlied@linux.ie>,
        Andrew Morton <akpm@linux-foundation.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        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 4:20 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

>
> 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