Re: [PATCH v3 5/5] x86/sgx: Remove redundant if conditions in sgx_encl_create

From: Greg KH <gregkh@linuxfoundation.org>
To: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Cc: Jarkko Sakkinen <jarkko@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Sean Christopherson <seanjc@google.com>,
	Shuah Khan <shuah@kernel.org>,
	x86@kernel.org, linux-sgx@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jia Zhang <zhang.jia@linux.alibaba.com>
Subject: Re: [PATCH v3 5/5] x86/sgx: Remove redundant if conditions in sgx_encl_create
Date: Sun, 24 Jan 2021 09:20:12 +0100	[thread overview]
Message-ID: <YA0tvOGp/shchVhu@kroah.com> (raw)
In-Reply-To: <20210124062907.88229-6-tianjia.zhang@linux.alibaba.com>

On Sun, Jan 24, 2021 at 02:29:07PM +0800, Tianjia Zhang wrote:
> In this scenario, there is no case where va_page is NULL, and
> the error has been checked. The if condition statement here is
> redundant, so remove the condition detection.
> 
> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> ---
>  arch/x86/kernel/cpu/sgx/ioctl.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index 1c6ecf9fbeff..b0b829f1b761 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -66,9 +66,11 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
>  	va_page = sgx_encl_grow(encl);
>  	if (IS_ERR(va_page))
>  		return PTR_ERR(va_page);
> -	else if (va_page)
> -		list_add(&va_page->list, &encl->va_pages);
> -	/* else the tail page of the VA page list had free slots. */
> +
> +	if (WARN_ONCE(!va_page, "non-empty VA page list before ECREATE"))
> +		return -EIO;

So you just crashed machines that have panic-on-warn enabled.  Don't do
that for no reason, just handle the error and move on.

thanks,

greg k-h