linux-kernel - Re: [PATCH] lib/vdso: Make clock

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Date:   Mon, 21 Oct 2019 17:23:42 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Andreas Schwab <schwab@...ux-m68k.org>
Cc:     Nathan Lynch <nathanl@...ux.ibm.com>,
        "linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] lib/vdso: Make clock_getres() POSIX compliant again



Le 21/10/2019 à 12:07, Thomas Gleixner a écrit :
> A recent commit removed the NULL pointer check from the clock_getres()
> implementation causing a test case to fault.
> 
> POSIX requires an explicit NULL pointer check for clock_getres() aside of
> the validity check of the clock_id argument for obscure reasons.
> 
> Add it back for both 32bit and 64bit.
> 
> Note, this is only a partial revert of the offending commit which does not
> bring back the broken fallback invocation in the the 32bit compat
> implementations of clock_getres() and clock_gettime().
> 
> Fixes: a9446a906f52 ("lib/vdso/32: Remove inconsistent NULL pointer checks")
> Reported-by: Andreas Schwab <schwab@...ux-m68k.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Tested-by: Christophe Leroy <christophe.leroy@....fr>

> Cc: stable@...r.kernel.org
> ---
>   lib/vdso/gettimeofday.c |    9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> --- a/lib/vdso/gettimeofday.c
> +++ b/lib/vdso/gettimeofday.c
> @@ -214,9 +214,10 @@ int __cvdso_clock_getres_common(clockid_
>   		return -1;
>   	}
>   
> -	res->tv_sec = 0;
> -	res->tv_nsec = ns;
> -
> +	if (likely(res)) {
> +		res->tv_sec = 0;
> +		res->tv_nsec = ns;
> +	}
>   	return 0;
>   }
>   
> @@ -245,7 +246,7 @@ static __maybe_unused int
>   		ret = clock_getres_fallback(clock, &ts);
>   #endif
>   
> -	if (likely(!ret)) {
> +	if (likely(!ret && res)) {
>   		res->tv_sec = ts.tv_sec;
>   		res->tv_nsec = ts.tv_nsec;
>   	}
>