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Message-ID: <202211171513.28D070E@keescook>
Date: Thu, 17 Nov 2022 15:14:31 -0800
From: Kees Cook <keescook@...omium.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: linux-kernel@...r.kernel.org,
Marc Kleine-Budde <mkl@...gutronix.de>,
Paolo Abeni <pabeni@...hat.com>,
Stefano Garzarella <sgarzare@...hat.com>,
Jakub Kicinski <kuba@...nel.org>,
Nikolay Aleksandrov <nikolay@...dia.com>,
"David S. Miller" <davem@...emloft.net>,
Florian Fainelli <f.fainelli@...il.com>,
netdev@...r.kernel.org,
"Gustavo A. R. Silva" <gustavo@...eddedor.com>,
linux-next@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: Coverity: __sock_gen_cookie(): Error handling issues
On Thu, Nov 17, 2022 at 02:49:55PM -0800, Eric Dumazet wrote:
> On Thu, Nov 17, 2022 at 2:22 PM coverity-bot <keescook@...omium.org> wrote:
> >
> > Hello!
> >
> > This is an experimental semi-automated report about issues detected by
> > Coverity from a scan of next-20221117 as part of the linux-next scan project:
> > https://scan.coverity.com/projects/linux-next-weekly-scan
> >
> > You're getting this email because you were associated with the identified
> > lines of code (noted below) that were touched by commits:
> >
> > Wed Nov 16 12:42:01 2022 +0000
> > 4ebf802cf1c6 ("net: __sock_gen_cookie() cleanup")
> >
> > Coverity reported the following:
> >
> > *** CID 1527347: Error handling issues (CHECKED_RETURN)
> > net/core/sock_diag.c:33 in __sock_gen_cookie()
> > 27 {
> > 28 u64 res = atomic64_read(&sk->sk_cookie);
> > 29
> > 30 if (!res) {
> > 31 u64 new = gen_cookie_next(&sock_cookie);
> > 32
> > vvv CID 1527347: Error handling issues (CHECKED_RETURN)
> > vvv Calling "atomic64_try_cmpxchg" without checking return value (as is done elsewhere 8 out of 9 times).
> > 33 atomic64_try_cmpxchg(&sk->sk_cookie, &res, new);
>
>
> Hmmm. for some reason I thought @res was always updated...
>
> A fix would be to read sk->sk_cookie, but I guess your tool will still
> complain we do not care
> of atomic64_try_cmpxchg() return value ?
>
> diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
> index b11593cae5a09b15a10d6ba35bccc22263cb8fc8..58efb9c1c8dd4f8e5a3009a0176e1b96487daaff
> 100644
> --- a/net/core/sock_diag.c
> +++ b/net/core/sock_diag.c
> @@ -31,6 +31,10 @@ u64 __sock_gen_cookie(struct sock *sk)
> u64 new = gen_cookie_next(&sock_cookie);
>
> atomic64_try_cmpxchg(&sk->sk_cookie, &res, new);
> + /* Another cpu/thread might have won the race,
> + * reload the final value.
> + */
> + res = atomic64_read(&sk->sk_cookie);
> }
> return res;
> }
I think it's saying it was expecting an update loop -- i.e. to make sure
the value actually got swapped (the "try" part...)?
--
Kees Cook
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