From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>
Cc: syzbot <syzbot+9ce030d4c89856b27619@syzkaller.appspotmail.com>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
"open list:HID CORE LAYER" <linux-input@vger.kernel.org>
Subject: Re: [syzbot] unexpected kernel reboot (4)
Date: Thu, 22 Apr 2021 19:16:31 +0900 [thread overview]
Message-ID: <abcb019f-a78a-3c6d-e199-719176a394d6@i-love.sakura.ne.jp> (raw)
In-Reply-To: <b8162e95-fb2e-51f6-9d9b-a4d64873876e@i-love.sakura.ne.jp>
On 2021/04/15 1:16, Tetsuo Handa wrote:
> On 2021/04/15 0:39, Andrey Konovalov wrote:
>> On Wed, Apr 14, 2021 at 7:45 AM Dmitry Vyukov <dvyukov@google.com> wrote:
>>>
>>> On Tue, Apr 13, 2021 at 11:27 PM syzbot
>>> <syzbot+9ce030d4c89856b27619@syzkaller.appspotmail.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> syzbot found the following issue on:
>>>>
>>>> HEAD commit: 89698bec Merge tag 'm68knommu-for-v5.12-rc7' of git://git...
>>>> git tree: upstream
>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1243fcfed00000
>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=b234ddbbe2953747
>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=9ce030d4c89856b27619
>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=173e92fed00000
>>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1735da2ed00000
>>>>
>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>> Reported-by: syzbot+9ce030d4c89856b27619@syzkaller.appspotmail.com
>>>>
>>>> output_len: 0x000000000e74eb68
>>>> kernel_total_size: 0x000000000f226000
>>>> needed_size: 0x000000000f400000
>>>> trampoline_32bit: 0x000000000009d000
>>>> Decompressing Linux... Parsing ELF... done.
>>>> Booting the kernel.
>>>
>>> +linux-input
>>>
>>> The reproducer connects some USB HID device and communicates with the driver.
>>> Previously we observed reboots because HID devices can trigger reboot
>>> SYSRQ, but we disable it with "CONFIG_MAGIC_SYSRQ is not set".
>>> How else can a USB device reboot the machine? Is it possible to disable it?
>>> I don't see any direct includes of <linux/reboot.h> in drivers/usb/*
>>
>> This happens when a keyboard sends the Ctrl+Alt+Del sequence, see
>> fn_boot_it()->ctrl_alt_del() in drivers/tty/vt/keyboard.c.
Hmm, maybe the reproducer I use and "#syz test:" uses differs.
But since "#syz test:" did not trigger the problem if
https://syzkaller.appspot.com/x/patch.diff?x=14ba0851d00000 is applied,
can we add
if (fork() == 0) {
char buf[20] = { };
int fd = open("/proc/sys/kernel/ctrl-alt-del", O_WRONLY);
write(fd, "0\n", 2);
close(fd);
fd = open("/proc/sys/kernel/cad_pid", O_WRONLY);
snprintf(buf, sizeof(buf) - 1, "%d\n", getpid());
write(fd, buf, strlen(buf));
close(fd);
}
to the common setup function? This will serve as a temporary workaround
until Linus accepts disable-specific-functionality changes.
There is no need to keep the process referenced by /proc/sys/kernel/cad_pid alive,
for "struct pid" which can remain after the process terminates is saved there.
next prev parent reply other threads:[~2021-04-22 10:16 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <000000000000301a4d05bfe14b8f@google.com>
2021-04-14 5:45 ` [syzbot] unexpected kernel reboot (4) Dmitry Vyukov
2021-04-14 15:39 ` Andrey Konovalov
2021-04-14 16:16 ` Tetsuo Handa
2021-04-22 10:16 ` Tetsuo Handa [this message]
2021-04-22 14:20 ` Dmitry Vyukov
2021-04-22 16:13 ` Tetsuo Handa
2021-04-22 17:00 ` Dmitry Vyukov
2021-04-17 3:19 ` Tetsuo Handa
2021-04-18 15:09 ` Tetsuo Handa
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