linux-kernel - Re: BUG: unable to handle kernel NULL pointer dereference in __syscall_return

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Date:   Mon, 29 Jun 2020 09:42:27 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     syzbot <syzbot+95910cea1a7ad8850a0f@...kaller.appspotmail.com>
Cc:     bp@...en8.de, hpa@...or.com, linux-kernel@...r.kernel.org,
        luto@...nel.org, mingo@...hat.com, syzkaller-bugs@...glegroups.com,
        tglx@...utronix.de, x86@...nel.org
Subject: Re: BUG: unable to handle kernel NULL pointer dereference in
 __syscall_return_slowpath

On Mon, Jun 29, 2020 at 09:31:16AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    4e99b321 Merge tag 'nfs-for-5.8-2' of git://git.linux-nfs...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=116abdd3100000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569
> dashboard link: https://syzkaller.appspot.com/bug?extid=95910cea1a7ad8850a0f
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> userspace arch: i386
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17020755100000

Looks like ioctl$FBIOPUT_VSCREENINFO on /dev/fb0 striking again.  There are like
20-30 open syzbot reports for this.

See https://lkml.kernel.org/lkml/000000000000ff323f05a053100c@google.com/T/#u
for some previous discussion.

#syz dup: general protection fault in syscall_return_slowpath