linux-kernel - Re: [RFC 2/3] futex: exit: Print a warning when futex

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Message-ID: <19b324a4-f69c-1624-fbc7-e178b7c31d81@redhat.com>
Date:   Fri, 22 Apr 2022 10:12:39 -0400
From:   Nico Pache <npache@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        André Almeida <andrealmeid@...labora.com>,
        Arjan van de Ven <arjan@...radead.org>,
        Ulrich Drepper <drepper@...hat.com>
Subject: Re: [RFC 2/3] futex: exit: Print a warning when futex_cleanup fails



On 4/21/22 15:30, Matthew Wilcox wrote:
> On Thu, Apr 21, 2022 at 03:05:32PM -0400, Nico Pache wrote:
>> @@ -1007,13 +1013,15 @@ static inline void exit_pi_state_list(struct task_struct *curr) { }
>>  static void futex_cleanup(struct task_struct *tsk)
>>  {
>>  	if (unlikely(tsk->robust_list)) {
>> -		exit_robust_list(tsk);
>> +		if (!exit_robust_list(tsk))
>> +			pr_info("futex: exit_robust_list failed");
> 
> Doesn't this allow a malicious user process to spam the kernel logs
> with messages?  There needs to be a ratelimit on this, at least.
Fair point, we'd need a ratelimited print if we want to continue forward with
this. Additionally we may want to limit this print to debug kernels, but thats
just a thought.

Thanks for the review :)
-- Nico