Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752024AbcDNVt4 (ORCPT ); Thu, 14 Apr 2016 17:49:56 -0400 Received: from mail-pf0-f181.google.com ([209.85.192.181]:35209 "EHLO mail-pf0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751498AbcDNVty (ORCPT ); Thu, 14 Apr 2016 17:49:54 -0400 Date: Thu, 14 Apr 2016 22:49:49 +0100 From: Matt Fleming To: Vaishali Thakkar Cc: linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, Julia Lawall , Saurabh Sengar Subject: Re: [PATCH] efi: Use GFP_ATOMIC instead of GFP_KERNEL Message-ID: <20160414214949.GS2829@codeblueprint.co.uk> References: <1460372009-10785-1-git-send-email-vaishali.thakkar@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1460372009-10785-1-git-send-email-vaishali.thakkar@oracle.com> User-Agent: Mutt/1.5.24+41 (02bc14ed1569) (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1356 Lines: 39 On Mon, 11 Apr, at 04:23:29PM, Vaishali Thakkar wrote: > Function dup_variable_bug is called inside the spinlock. > This may lead to issues when kzalloc sleeps, so it is > better to use GFP_ATOMIC in this spinlocked context. > > Problem found using Coccinelle. Dang it, I broke coccinelle ;) > Signed-off-by: Vaishali Thakkar > --- > drivers/firmware/efi/vars.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c > index 0ac594c..d5e2f28 100644 > --- a/drivers/firmware/efi/vars.c > +++ b/drivers/firmware/efi/vars.c > @@ -411,7 +411,7 @@ static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid, > */ > efivar_wq_enabled = false; > > - str8 = kzalloc(len8, GFP_KERNEL); > + str8 = kzalloc(len8, GFP_ATOMIC); > if (!str8) > return; > This was brought up by Saurabh last year, https://lkml.kernel.org/r/1446003747-3760-1-git-send-email-saurabh.truth@gmail.com dup_variable_bug() is never called while holding the spinlock in practice, and I'm guessing Coccinelle cannot understand that because it'd need to look at program control flow, across multiple compilation units. If anyone wants to send a patch to clean up the EFI code so that it's easier for coccinelle to check it, I'd be happy to review it.