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Date: Thu, 9 Mar 2017 07:48:03 -0800
From: Thomas Garnier <thgarnie@...gle.com>
To: Borislav Petkov <bp@...en8.de>
Cc: David Howells <dhowells@...hat.com>, Dave Hansen <dave.hansen@...el.com>, 
	Arnd Bergmann <arnd@...db.de>, Al Viro <viro@...iv.linux.org.uk>, 
	René Nyffenegger <mail@...enyffenegger.ch>, 
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	Andy Lutomirski <luto@...nel.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, 
	Nicolas Pitre <nicolas.pitre@...aro.org>, Petr Mladek <pmladek@...e.com>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, 
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	Will Deacon <will.deacon@....com>, Catalin Marinas <catalin.marinas@....com>, 
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	Pratyush Anand <panand@...hat.com>, Vladimir Murzin <vladimir.murzin@....com>, 
	Chris Metcalf <cmetcalf@...lanox.com>, Andre Przywara <andre.przywara@....com>, 
	Linux API <linux-api@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	"the arch/x86 maintainers" <x86@...nel.org>, linux-arm-kernel@...ts.infradead.org, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v2 1/4] syscalls: Restore address limit after a syscall

On Thu, Mar 9, 2017 at 12:42 AM, Borislav Petkov <bp@...en8.de> wrote:
> 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;
> }
>

I agree, cleaner. I will look to do this change on next iteration.

> --
> Regards/Gruss,
>     Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.



-- 
Thomas

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