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Message-ID: <1516848563.8378.60.camel@perches.com>
Subject: Re: [PATCH] x86: efi: Replace GFP_ATOMIC with GFP_KERNEL in
 efi_query_variable_store
From:   Joe Perches <joe@perches.com>
To:     Jia-Ju Bai <baijiaju1990@gmail.com>, matt@codeblueprint.co.uk,
        ard.biesheuvel@linaro.org, tglx@linutronix.de, mingo@redhat.com,
        hpa@zytor.com
Cc:     x86@kernel.org, linux-efi@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Wed, 24 Jan 2018 18:49:23 -0800
In-Reply-To: <1516847386-5291-1-git-send-email-baijiaju1990@gmail.com>
References: <1516847386-5291-1-git-send-email-baijiaju1990@gmail.com>
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On Thu, 2018-01-25 at 10:29 +0800, Jia-Ju Bai wrote:
> The function kzalloc here is not called in atomic context.
> If nonblocking in efi_query_variable_store is true, 
> namely it is in atomic context, efi_query_variable_store will return before
> this kzalloc is called.
> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.
> 
> This is found by a static analysis tool named DCNS written by myself.
[]
> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
[]
> @@ -177,7 +177,7 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size,
>  		 * that by attempting to use more space than is available.
>  		 */
>  		unsigned long dummy_size = remaining_size + 1024;
> -		void *dummy = kzalloc(dummy_size, GFP_ATOMIC);
> +		void *dummy = kzalloc(dummy_size, GFP_KERNEL);

trivially, kzalloc takes a size_t not an unsigned long
and this _could_, though probably doesn't, lose precision.

It might be nicer to convert to size_t where appropriate.