linux-kernel - Re: [PATCH] seccomp: Only dump core when single-threaded

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Date:   Tue, 14 Feb 2017 11:09:22 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Andrei Vagin <avagin@...tuozzo.com>,
        James Morris <james.l.morris@...cle.com>
Cc:     Mike Frysinger <vapier@...too.org>,
        Paul Moore <paul@...l-moore.com>,
        Tyler Hicks <tyhicks@...onical.com>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] seccomp: Only dump core when single-threaded

On Mon, Feb 13, 2017 at 10:37 PM, Andrei Vagin <avagin@...tuozzo.com> wrote:
> On Tue, Feb 07, 2017 at 03:18:51PM -0800, Kees Cook wrote:
>> The SECCOMP_RET_KILL filter return code has always killed the current
>> thread, not the entire process. Changing this as a side-effect of dumping
>> core isn't a safe thing to do (a few test suites have already flagged this
>> behavioral change). Instead, restore the RET_KILL semantics, but still
>> dump core when a RET_KILL delivers SIGSYS to a single-threaded process.
>>
>> Fixes: b25e67161c29 ("seccomp: dump core when using SECCOMP_RET_KILL")
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>
> All CRIU tests passed with this patch. Thanks!
>
> Acked-by: Andrei Vagin <avagin@...tuozzo.com>

Thanks for testing!

James, can you make sure this makes it into your -next tree for v4.11?

Thanks!

-Kees

>
>> ---
>>  kernel/seccomp.c | 13 ++++++++-----
>>  1 file changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
>> index f8f88ebcb3ba..e15185c28de5 100644
>> --- a/kernel/seccomp.c
>> +++ b/kernel/seccomp.c
>> @@ -643,11 +643,14 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
>>       default: {
>>               siginfo_t info;
>>               audit_seccomp(this_syscall, SIGSYS, action);
>> -             /* Show the original registers in the dump. */
>> -             syscall_rollback(current, task_pt_regs(current));
>> -             /* Trigger a manual coredump since do_exit skips it. */
>> -             seccomp_init_siginfo(&info, this_syscall, data);
>> -             do_coredump(&info);
>> +             /* Dump core only if this is the last remaining thread. */
>> +             if (get_nr_threads(current) == 1) {
>> +                     /* Show the original registers in the dump. */
>> +                     syscall_rollback(current, task_pt_regs(current));
>> +                     /* Trigger a manual coredump since do_exit skips it. */
>> +                     seccomp_init_siginfo(&info, this_syscall, data);
>> +                     do_coredump(&info);
>> +             }
>>               do_exit(SIGSYS);
>>       }
>>       }
>> --
>> 2.7.4
>>
>>
>> --
>> Kees Cook
>> Pixel Security



-- 
Kees Cook
Pixel Security