linux-kernel - Re: [PATCH v4] x86/fsgsbase/64: Fix the base write helper functions

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Message-ID: <7A9F766D-333A-4ED5-8C3C-AE3BEBE39C69@intel.com>
Date:   Fri, 16 Nov 2018 23:27:27 +0000
From:   "Bae, Chang Seok" <chang.seok.bae@...el.com>
To:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/fsgsbase/64: Fix the base write helper functions

> On Nov 14, 2018, at 13:46, Bae, Chang Seok <chang.seok.bae@...el.com> wrote:
> 
> int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> @@ -758,11 +720,45 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
> 
> 	switch (option) {
> 	case ARCH_SET_GS: {
> -		ret = x86_gsbase_write_task(task, arg2);
> +		preempt_disable();
> +		if (unlikely(arg2 >= TASK_SIZE_MAX))
> +			return -EPERM;

Sorry, preempt_disabled() should go after this.
Chang