From mboxrd@z Thu Jan  1 00:00:00 1970
From: bp@alien8.de (Borislav Petkov)
Date: Thu, 9 Mar 2017 09:42:08 +0100
Subject: [PATCH v2 1/4] syscalls: Restore address limit after a syscall
In-Reply-To: <20170309012456.5631-1-thgarnie@google.com>
References: <20170309012456.5631-1-thgarnie@google.com>
Message-ID: <20170309084208.ims3ehcnieo7uqew@pd.tnic>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wed, Mar 08, 2017 at 05:24:53PM -0800, Thomas Garnier wrote:
> @@ -191,6 +191,22 @@ extern struct trace_event_functions exit_syscall_print_funcs;
>  	SYSCALL_METADATA(sname, x, __VA_ARGS__)			\
>  	__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
>  
> +asmlinkage void verify_pre_usermode_state(void);
> +
> +#ifndef CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> +static inline bool has_user_ds(void) {
> +	bool ret = segment_eq(get_fs(), USER_DS);
> +	// Prevent re-ordering the call

This is not the kernel comments style. Use /* */ instead.

> +	barrier();
> +	return ret;
> +}
> +#else
> +static inline bool has_user_ds(void) {
> +	return false;
> +}
> +#endif

... and then you could slim down the ifdeffery a bit:

static inline bool has_user_ds(void) {
	bool ret = false;

#ifndef CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
	ret = segment_eq(get_fs(), USER_DS);
	/* Prevent re-ordering the call. */
	barrier();
#endif

	return ret;
}

-- 
Regards/Gruss,
    Boris.

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