linux-kernel - Re: [PATCH] seccomp: Add SECCOMP_CLONE

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Message-ID: <42cf76db-6cda-4606-9128-6f433da57d48@oracle.com>
Date: Wed, 3 Sep 2025 14:51:54 -0600
From: Tom Hromatka <tom.hromatka@...cle.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Kees Cook <kees@...nel.org>, Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>, Sargun Dhillon <sargun@...gun.me>,
        Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH] seccomp: Add SECCOMP_CLONE_FILTER operation

On 9/3/25 2:45 PM, Alexei Starovoitov wrote:
> On Wed, Sep 3, 2025 at 1:38 PM Tom Hromatka <tom.hromatka@...cle.com> wrote:
>>
>> +
>> +       spin_lock_irq(&current->sighand->siglock);
>> +       spin_lock_irq(&task->sighand->siglock);
>> +
>> +       if (atomic_read(&task->seccomp.filter_count) == 0) {
>> +               spin_unlock_irq(&task->sighand->siglock);
>> +               spin_unlock_irq(&current->sighand->siglock);
> 
> did you copy this pattern from somewhere ?
> It's obviously buggy.

I tried to mimic the logic in copy_seccomp() in kernel/fork.c,
but as you point out, I probably messed it up :).

Do you have recommendations for a better design pattern?

Thanks!

Tom