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SubjectRe: [patch 5/5] arm64: compat: vdso: Use legacy syscalls as fallback
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On 7/28/19 2:12 PM, Thomas Gleixner wrote:
> The generic VDSO implementation uses the Y2038 safe clock_gettime64() and
> clock_getres_time64() syscalls as fallback for 32bit VDSO. This breaks
> seccomp setups because these syscalls might be not (yet) allowed.
>
> Implement the 32bit variants which use the legacy syscalls and select the
> variant in the core library.
>
> The 64bit time variants are not removed because they are required for the
> time64 based vdso accessors.
>

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> Reported-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Reported-by: Paul Bolle <pebolle@tiscali.nl>
> Suggested-by: Andy Lutomirski <luto@kernel.org>
> Fixes: 00b26474c2f1 ("lib/vdso: Provide generic VDSO implementation")
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> Note:
>
> The NULL pointer check in the getres/getres32() fallbacks is just wrong.
> The proper return code for a NULL pointer is -EFAULT. How did this ever
> pass any posix test? Also it just should go away because any other invalid
> pointer will be caught in the syscall anyway. The clockid check is also
> part of the syscall so no point in having it here again. Handling calls
> with invalid arguments is not really a performance critical operation.
>
> ---
> arch/arm64/include/asm/vdso/compat_gettimeofday.h | 40 ++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
>
> --- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h
> +++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
> @@ -16,6 +16,8 @@
>
> #define VDSO_HAS_CLOCK_GETRES 1
>
> +#define VDSO_HAS_32BIT_FALLBACK 1
> +
> static __always_inline
> int gettimeofday_fallback(struct __kernel_old_timeval *_tv,
> struct timezone *_tz)
> @@ -52,6 +54,23 @@ long clock_gettime_fallback(clockid_t _c
> }
>
> static __always_inline
> +long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
> +{
> + register struct old_timespec32 *ts asm("r1") = _ts;
> + register clockid_t clkid asm("r0") = _clkid;
> + register long ret asm ("r0");
> + register long nr asm("r7") = __NR_compat_clock_gettime;
> +
> + asm volatile(
> + " swi #0\n"
> + : "=r" (ret)
> + : "r" (clkid), "r" (ts), "r" (nr)
> + : "memory");
> +
> + return ret;
> +}
> +
> +static __always_inline
> int clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
> {
> register struct __kernel_timespec *ts asm("r1") = _ts;
> @@ -61,6 +80,27 @@ int clock_getres_fallback(clockid_t _clk
>
> /* The checks below are required for ABI consistency with arm */
> if ((_clkid >= MAX_CLOCKS) && (_ts == NULL))
> + return -EINVAL;
> +
> + asm volatile(
> + " swi #0\n"
> + : "=r" (ret)
> + : "r" (clkid), "r" (ts), "r" (nr)
> + : "memory");
> +
> + return ret;
> +}
> +
> +static __always_inline
> +int clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
> +{
> + register struct old_timespec32 *ts asm("r1") = _ts;
> + register clockid_t clkid asm("r0") = _clkid;
> + register long ret asm ("r0");
> + register long nr asm("r7") = __NR_compat_clock_getres;
> +
> + /* The checks below are required for ABI consistency with arm */
> + if ((_clkid >= MAX_CLOCKS) && (_ts == NULL))
> return -EINVAL;
>
> asm volatile(
>
>

--
Regards,
Vincenzo

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