linux-kernel - Re: [PATCH v4 18/26] arm64: vdso32: Replace TASK_SIZE

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Message-ID: <20200317143834.GC632169@arrakis.emea.arm.com>
Date:   Tue, 17 Mar 2020 14:38:34 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        linux-mips@...r.kernel.org, x86@...nel.org,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Paul Burton <paul.burton@...s.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...nvz.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <Mark.Rutland@....com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v4 18/26] arm64: vdso32: Replace TASK_SIZE_32 check in
 vgettimeofday

On Tue, Mar 17, 2020 at 12:22:12PM +0000, Vincenzo Frascino wrote:
> diff --git a/arch/arm64/kernel/vdso32/vgettimeofday.c b/arch/arm64/kernel/vdso32/vgettimeofday.c
> index 54fc1c2ce93f..91138077b073 100644
> --- a/arch/arm64/kernel/vdso32/vgettimeofday.c
> +++ b/arch/arm64/kernel/vdso32/vgettimeofday.c
> @@ -8,11 +8,14 @@
>  #include <linux/time.h>
>  #include <linux/types.h>
>  
> +#define VALID_CLOCK_ID(x) \
> +	((x >= 0) && (x < VDSO_BASES))
> +
>  int __vdso_clock_gettime(clockid_t clock,
>  			 struct old_timespec32 *ts)
>  {
>  	/* The checks below are required for ABI consistency with arm */
> -	if ((u32)ts >= TASK_SIZE_32)
> +	if ((u32)ts > UINTPTR_MAX - sizeof(*ts) + 1)
>  		return -EFAULT;
>  
>  	return __cvdso_clock_gettime32(clock, ts);

I probably miss something but I can't find the TASK_SIZE check in the
arch/arm/vdso/vgettimeofday.c code. Is this done elsewhere?

> @@ -22,7 +25,7 @@ int __vdso_clock_gettime64(clockid_t clock,
>  			   struct __kernel_timespec *ts)
>  {
>  	/* The checks below are required for ABI consistency with arm */
> -	if ((u32)ts >= TASK_SIZE_32)
> +	if ((u32)ts > UINTPTR_MAX - sizeof(*ts) + 1)
>  		return -EFAULT;
>  
>  	return __cvdso_clock_gettime(clock, ts);
> @@ -38,9 +41,12 @@ int __vdso_clock_getres(clockid_t clock_id,
>  			struct old_timespec32 *res)
>  {
>  	/* The checks below are required for ABI consistency with arm */
> -	if ((u32)res >= TASK_SIZE_32)
> +	if ((u32)res > UINTPTR_MAX - sizeof(res) + 1)
>  		return -EFAULT;
>  
> +	if (!VALID_CLOCK_ID(clock_id) && res == NULL)
> +		return -EINVAL;

This last check needs an explanation. If the clock_id is invalid but res
is not NULL, we allow it. I don't see where the compatibility issue is,
arm32 doesn't have such check.

-- 
Catalin