linux-kernel - Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1

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Message-ID: <AM6PR03MB5170BC4A276D72EA54398C58E4AA0@AM6PR03MB5170.eurprd03.prod.outlook.com>
Date:   Thu, 30 Apr 2020 16:29:47 +0200
From:   Bernd Edlinger <bernd.edlinger@...mail.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Jann Horn <jannh@...gle.com>, Oleg Nesterov <oleg@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Waiman Long <longman@...hat.com>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexey Gladkov <gladkov.alexey@...il.com>
Subject: Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1

Hi Linus,

On 4/30/20 3:47 PM, Linus Torvalds wrote:
> On Thu, Apr 30, 2020 at 6:39 AM Bernd Edlinger
> <bernd.edlinger@...mail.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.
> 

Ah, now I see, that was of course not the intended effect,
but that is not where the pseudo-deadlock happens at all,
would returning -RESTARTNOINTR in this function make this
patch acceptable, it will not have an effect on the test case?


Bernd.

> 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
>