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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 30 Apr 2020 06:47:41 -0700
Message-ID: <CAHk-=wiOdXfMa35bwCNfCNSsAndO-hFmsSNRWEEDziA1iDYGjg@mail.gmail.com>
Subject: Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1
To:     Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc:     Jann Horn <jannh@google.com>, Oleg Nesterov <oleg@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Waiman Long <longman@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, Will Deacon <will@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexey Gladkov <gladkov.alexey@gmail.com>
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On Thu, Apr 30, 2020 at 6:39 AM Bernd Edlinger
<bernd.edlinger@hotmail.de> wrote:
>
> Excuse me, but what in my /proc folder there is no attr/something
> is there a procfs equivalent of pthread_attach ?
>
> What exactly is "attr/something" ?

Anything that uses that proc_pid_attr_write().

Which you should have realized, since you wrote the patch that changed
that function to return -EAGAIN.

That's

    /proc/<pid>/attr/{current,exec,fscreate,keycreate,prev,sockcreate}

and some smack files.

Your patch definitely made them return -EINVAL if they happen in that
execve() black hole, instead of waiting for the execve() to just
complete and then just work.

Dropping a lock really is broken. It';s broken even if you then set a
flag saying "I dropped the lock, now you can't use it".

                  Linus