linux-kernel - Re: [PATCH 29/29] x86/fpu: Defer FPU state load until return to userspace

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Message-ID: <20181210144158.46sbqy5b3lkhcra5@linutronix.de>
Date:   Mon, 10 Dec 2018 15:41:58 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 29/29] x86/fpu: Defer FPU state load until return to
 userspace

On 2018-11-28 23:20:35 [+0100], To linux-kernel@...r.kernel.org wrote:
> --- a/arch/x86/kernel/fpu/signal.c
> +++ b/arch/x86/kernel/fpu/signal.c
> @@ -228,13 +228,12 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
>  	struct task_struct *tsk = current;
>  	struct fpu *fpu = &tsk->thread.fpu;
>  	int state_size = fpu_kernel_xstate_size;
> -	union fpregs_state *state;
> -	void *tmp;
>  	struct user_i387_ia32_struct env;
>  	struct user_i387_ia32_struct *envp = NULL;
>  	int ret = 0;
>  	u64 xfeatures = 0;
>  	int fx_only = 0;
> +	int err;
>  
…
>  	} else if (use_fxsr()) {
> -		ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
> -		if (ret)
> +		ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
> +		if (ret) {
> +			err = -EFAULT;
>  			goto err_out;
> +		}

After reworking the series after addressing the comments for 08/29 I
noticed that `err' should have been `ret'. 

Sebastian