linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Thomas Gleixner <tglx@linutronix.de>
To: Lukas Bulwahn <lukas.bulwahn@gmail.com>, Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Subject: Re: Question on commit dc7109aaa233 ("futex: Validate waiter correctly in futex_proxy_trylock_atomic()")
Date: Tue, 31 Aug 2021 01:29:40 +0200	[thread overview]
Message-ID: <87a6kyfr4r.ffs@tglx> (raw)
In-Reply-To: <CAKXUXMzqmN1dYpbYSCXWN9VwHn8+MXj3P=G09qD6=atwrcJ8WA@mail.gmail.com>

Lukas,

On Fri, Aug 20 2021 at 13:17, Lukas Bulwahn wrote:
> in commit dc7109aaa233 ("futex: Validate waiter correctly in
> futex_proxy_trylock_atomic()") visible on next-20210819, you add:
>
> +    /*
> +     * Ensure that this is a waiter sitting in futex_wait_requeue_pi()
> +     * and waiting on the 'waitqueue' futex which is always !PI.
> +     */
> +    if (!top_waiter->rt_waiter || top_waiter->pi_state)
> +        ret = -EINVAL;
>
> However, ret is unconditionally reassigned later and erases any
> intended effect of this assignment. This is making that assignment
> above a Dead Store, which clang-analyzer correctly warns about and
> which motivates me to write you an email.
>
> Did you intend to return -EINVAL here? So:
>
> +       if (!top_waiter->rt_waiter || top_waiter->pi_state)
> +               return -EINVAL;

Duh, yes.

> Static analysis tools are as foolish as they are... but every dog has its day...

IOW: Even a blind hen sometimes finds a grain of corn :)

Care to send a patch?

Thanks,

        tglx

  reply	other threads:[~2021-08-30 23:29 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20 11:17 Question on commit dc7109aaa233 ("futex: Validate waiter correctly in futex_proxy_trylock_atomic()") Lukas Bulwahn
2021-08-30 23:29 ` Thomas Gleixner [this message]
2021-09-01 18:28   ` André Almeida
2021-09-01 19:19     ` Thomas Gleixner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87a6kyfr4r.ffs@tglx \
    --to=tglx@linutronix.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lukas.bulwahn@gmail.com \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=sudipm.mukherjee@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).