Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932195AbdHYKlB (ORCPT ); Fri, 25 Aug 2017 06:41:01 -0400 Received: from mx02-sz.bfs.de ([194.94.69.103]:8497 "EHLO mx02-sz.bfs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754518AbdHYKk7 (ORCPT ); Fri, 25 Aug 2017 06:40:59 -0400 Message-ID: <599FFEB6.4070707@bfs.de> Date: Fri, 25 Aug 2017 12:40:54 +0200 From: walter harms Reply-To: wharms@bfs.de User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; de; rv:1.9.1.16) Gecko/20101125 SUSE/3.0.11 Thunderbird/3.0.11 MIME-Version: 1.0 To: Borislav Petkov CC: x86-ml , Dan Carpenter , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] x86/microcode/intel: Improve microcode patches saving flow References: <20170822211335.r7wcfcisdlq2xwgz@pd.tnic> <20170824201557.ev4ebslf6sg6xmne@mwanda> <20170824204714.jedeaphwmou5qafd@pd.tnic> <20170824205510.zy574qloxb4tsokq@mwanda> <20170824205844.3wkrq6vb7kv45vnv@pd.tnic> <20170824210847.hypvvpzf5pjhppyt@mwanda> <20170824211205.jpvmzzrm72vcb4xf@pd.tnic> <20170825090626.okc6reqltb5k4hip@pd.tnic> <20170825091228.acxl2pizbqe7ijnf@mwanda> <20170825091406.zytkd2pb5v6zxzrz@pd.tnic> <20170825100456.n236w3jebteokfd6@pd.tnic> In-Reply-To: <20170825100456.n236w3jebteokfd6@pd.tnic> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3258 Lines: 110 Am 25.08.2017 12:04, schrieb Borislav Petkov: > From: Borislav Petkov > > Avoid potentially dereferencing a NULL pointer when saving a microcode > patch for early loading on the application processors. > > While at it, drop the IS_ERR() checking in favor of simpler, NULL-ptr > checks which are sufficient and rename __alloc_microcode_buf() to > memdup_patch() to more precisely denote what it does. > > No functionality change. > > Reported-by: Dan Carpenter > Signed-off-by: Borislav Petkov > --- > arch/x86/kernel/cpu/microcode/intel.c | 27 ++++++++++++++------------- > 1 file changed, 14 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c > index 59edbe9d4ccb..8f7a9bbad514 100644 > --- a/arch/x86/kernel/cpu/microcode/intel.c > +++ b/arch/x86/kernel/cpu/microcode/intel.c > @@ -146,18 +146,18 @@ static bool microcode_matches(struct microcode_header_intel *mc_header, > return false; > } > > -static struct ucode_patch *__alloc_microcode_buf(void *data, unsigned int size) > +static struct ucode_patch *memdup_patch(void *data, unsigned int size) > { > struct ucode_patch *p; > > p = kzalloc(sizeof(struct ucode_patch), GFP_KERNEL); > if (!p) > - return ERR_PTR(-ENOMEM); > + return NULL; > > p->data = kmemdup(data, size, GFP_KERNEL); > if (!p->data) { > kfree(p); > - return ERR_PTR(-ENOMEM); > + return NULL; > } > > return p; > @@ -183,8 +183,8 @@ static void save_microcode_patch(void *data, unsigned int size) > if (mc_hdr->rev <= mc_saved_hdr->rev) > continue; > > - p = __alloc_microcode_buf(data, size); > - if (IS_ERR(p)) > + p = memdup_patch(data, size); > + if (!p) > pr_err("Error allocating buffer %p\n", data); > else > list_replace(&iter->plist, &p->plist); > @@ -196,24 +196,25 @@ static void save_microcode_patch(void *data, unsigned int size) > * newly found. > */ > if (!prev_found) { > - p = __alloc_microcode_buf(data, size); > - if (IS_ERR(p)) > + p = memdup_patch(data, size); > + if (!p) > pr_err("Error allocating buffer for %p\n", data); > else > list_add_tail(&p->plist, µcode_cache); > } > > + if (!p) > + return; > + just a bit nitpicking, i would expect something like that: p = memdup_patch(data, size); if (!p) { pr_err("Error allocating buffer for %p\n", data); return; } list_add_tail(&p->plist, µcode_cache); ... because this is a normal pattern for OOF conditions and everyone will ask "Why continue when there is no memory" just my 2 cents re, wh > /* > * Save for early loading. On 32-bit, that needs to be a physical > * address as the APs are running from physical addresses, before > * paging has been enabled. > */ > - if (p) { > - if (IS_ENABLED(CONFIG_X86_32)) > - intel_ucode_patch = (struct microcode_intel *)__pa_nodebug(p->data); > - else > - intel_ucode_patch = p->data; > - } > + if (IS_ENABLED(CONFIG_X86_32)) > + intel_ucode_patch = (struct microcode_intel *)__pa_nodebug(p->data); > + else > + intel_ucode_patch = p->data; > } > > static int microcode_sanity_check(void *mc, int print_err)