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[209.132.180.67]) by mx.google.com with ESMTP id y5si1597541pgb.43.2018.02.28.15.26.55; Wed, 28 Feb 2018 15:27:10 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=cmu.edu Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964978AbeB1X0O (ORCPT + 99 others); Wed, 28 Feb 2018 18:26:14 -0500 Received: from SMTP.ANDREW.CMU.EDU ([128.2.105.203]:55900 "EHLO smtp.andrew.cmu.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964903AbeB1X0M (ORCPT ); Wed, 28 Feb 2018 18:26:12 -0500 Received: from crash.ini.cmu.edu (205.153.92.177.IPYX-135073-ZYO.above.net [205.153.92.177] (may be forged)) (user=somlo mech=LOGIN (0 bits)) by smtp.andrew.cmu.edu (8.15.2/8.15.2) with ESMTPSA id w1SNPw0b040763 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 28 Feb 2018 18:26:04 -0500 Date: Wed, 28 Feb 2018 18:25:58 -0500 From: Gabriel Somlo To: "Michael S. Tsirkin" Cc: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , open list , slp@redhat.com, bhe@redhat.com, xiaolong.ye@intel.com Subject: Re: [PATCH v15 08/11] fw_cfg: handle fw_cfg_read_blob() error Message-ID: <20180228232551.GA23743@crash.ini.cmu.edu> References: <20180215213312.29234-1-marcandre.lureau@redhat.com> <20180215213312.29234-9-marcandre.lureau@redhat.com> <20180227021150-mutt-send-email-mst@kernel.org> <20180228173014-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180228173014-mutt-send-email-mst@kernel.org> X-Clacks-Overhead: GNU Terry Pratchett User-Agent: Mutt/1.9.2 (2017-12-15) X-PMX-Version: 6.3.0.2556906, Antispam-Engine: 2.7.2.2107409, Antispam-Data: 2018.2.28.231816 X-SMTP-Spam-Clean: 8% ( MULTIPLE_RCPTS 0.1, HTML_00_01 0.05, HTML_00_10 0.05, BODY_SIZE_6000_6999 0, BODY_SIZE_7000_LESS 0, DATE_TZ_NA 0, FROM_EDU_TLD 0, IN_REP_TO 0, LEGITIMATE_SIGNS 0, MSG_THREAD 0, MULTIPLE_REAL_RCPTS 0, NO_URI_HTTPS 0, RDNS_GENERIC_POOLED 0, RDNS_SUSP 0, RDNS_SUSP_GENERIC 0, REFERENCES 0, __ANY_URI 0, __BOUNCE_CHALLENGE_SUBJ 0, __BOUNCE_NDR_SUBJ_EXEMPT 0, __CC_NAME 0, __CC_NAME_DIFF_FROM_ACC 0, __CC_REAL_NAMES 0, __CD 0, __CT 0, __CTE 0, __CT_TEXT_PLAIN 0, __FORWARDED_MSG 0, __HAS_CC_HDR 0, __HAS_FROM 0, __HAS_MSGID 0, __INVOICE_MULTILINGUAL 0, __IN_REP_TO 0, __MIME_TEXT_ONLY 0, __MIME_TEXT_P 0, __MIME_TEXT_P1 0, __MIME_VERSION 0, __MULTIPLE_RCPTS_CC_X2 0, __NO_HTML_TAG_RAW 0, __PHISH_SPEAR_STRUCTURE_1 0, __REFERENCES 0, __SANE_MSGID 0, __SUBJ_ALPHA_END 0, __SUBJ_ALPHA_NEGATE 0, __TO_MALFORMED_2 0, __TO_NAME 0, __TO_NAME_DIFF_FROM_ACC 0, __TO_REAL_NAMES 0, __URI_NO_WWW 0, __URI_NS , __USER_AGENT 0) X-SMTP-Spam-Score: 8% X-Scanned-By: MIMEDefang 2.78 on 128.2.105.203 X-Scanned-By: MIMEDefang 2.78 on 128.2.105.203 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 28, 2018 at 05:32:52PM +0200, Michael S. Tsirkin wrote: > On Wed, Feb 28, 2018 at 12:49:35PM +0100, Marc-Andr? Lureau wrote: > > Hi > > > > On Tue, Feb 27, 2018 at 1:20 AM, Michael S. Tsirkin wrote: > > > On Thu, Feb 15, 2018 at 10:33:09PM +0100, Marc-Andr? Lureau wrote: > > >> fw_cfg_read_blob() may fail, but does not return error. This may lead > > >> to undefined behaviours, such as a memcmp(sig, "QEMU") on uninitilized > > >> memory. > > > > > > I don't think that's true - there's a memset there that > > > will initialize the memory. probe is likely the only > > > case where it returns a slightly incorrect data. > > > > Right, I'll update the commit message. > > > > >> Return an error if ACPI locking failed. Also, the following > > >> DMA read/write extension will add more error paths that should be > > >> handled appropriately. > > >> > > >> Signed-off-by: Marc-Andr? Lureau > > >> --- > > >> drivers/firmware/qemu_fw_cfg.c | 32 ++++++++++++++++++++++---------- > > >> 1 file changed, 22 insertions(+), 10 deletions(-) > > >> > > >> diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c > > >> index f6f90bef604c..5e6e5ac71dab 100644 > > >> --- a/drivers/firmware/qemu_fw_cfg.c > > >> +++ b/drivers/firmware/qemu_fw_cfg.c > > >> @@ -59,8 +59,8 @@ static void fw_cfg_sel_endianness(u16 key) > > >> } > > >> > > >> /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */ > > >> -static void fw_cfg_read_blob(u16 key, > > >> - void *buf, loff_t pos, size_t count) > > >> +static ssize_t fw_cfg_read_blob(u16 key, > > >> + void *buf, loff_t pos, size_t count) > > >> { > > >> u32 glk = -1U; > > >> acpi_status status; > > >> @@ -73,7 +73,7 @@ static void fw_cfg_read_blob(u16 key, > > >> /* Should never get here */ > > >> WARN(1, "fw_cfg_read_blob: Failed to lock ACPI!\n"); > > >> memset(buf, 0, count); > > >> - return; > > >> + return -EINVAL; > > >> } > > >> > > >> mutex_lock(&fw_cfg_dev_lock); > > > > > > Wouldn't something like -EBUSY be more appropriate? > > > > In theory, it would be a general failure right? I don't think we want > > the caller to retry. I think in EINVAL fits better, but I don't think > > it matters much this or EBUSY. > > > > >> @@ -84,6 +84,7 @@ static void fw_cfg_read_blob(u16 key, > > >> mutex_unlock(&fw_cfg_dev_lock); > > >> > > >> acpi_release_global_lock(glk); > > >> + return count; > > >> } > > >> > > >> /* clean up fw_cfg device i/o */ > > >> @@ -165,8 +166,9 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev) > > >> } > > >> > > >> /* verify fw_cfg device signature */ > > >> - fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE); > > >> - if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) { > > >> + if (fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, > > >> + 0, FW_CFG_SIG_SIZE) < 0 || > > >> + memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) { > > >> fw_cfg_io_cleanup(); > > >> return -ENODEV; > > >> } > > >> @@ -326,8 +328,7 @@ static ssize_t fw_cfg_sysfs_read_raw(struct file *filp, struct kobject *kobj, > > >> if (count > entry->size - pos) > > >> count = entry->size - pos; > > >> > > >> - fw_cfg_read_blob(entry->select, buf, pos, count); > > >> - return count; > > >> + return fw_cfg_read_blob(entry->select, buf, pos, count); > > >> } > > >> > > >> static struct bin_attribute fw_cfg_sysfs_attr_raw = { > > >> @@ -483,7 +484,11 @@ static int fw_cfg_register_dir_entries(void) > > >> struct fw_cfg_file *dir; > > >> size_t dir_size; > > >> > > >> - fw_cfg_read_blob(FW_CFG_FILE_DIR, &files_count, 0, sizeof(files_count)); > > >> + ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, &files_count, > > >> + 0, sizeof(files_count)); > > >> + if (ret < 0) > > >> + return ret; > > >> + > > >> count = be32_to_cpu(files_count); > > >> dir_size = count * sizeof(struct fw_cfg_file); > > >> > > >> @@ -491,7 +496,10 @@ static int fw_cfg_register_dir_entries(void) > > >> if (!dir) > > >> return -ENOMEM; > > >> > > >> - fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, sizeof(files_count), dir_size); > > >> + ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, > > >> + sizeof(files_count), dir_size); > > >> + if (ret < 0) > > >> + goto end; > > >> > > >> for (i = 0; i < count; i++) { > > >> ret = fw_cfg_register_file(&dir[i]); > > >> @@ -499,6 +507,7 @@ static int fw_cfg_register_dir_entries(void) > > >> break; > > >> } > > >> > > >> +end: > > >> kfree(dir); > > >> return ret; > > >> } > > >> @@ -539,7 +548,10 @@ static int fw_cfg_sysfs_probe(struct platform_device *pdev) > > >> goto err_probe; > > >> > > >> /* get revision number, add matching top-level attribute */ > > >> - fw_cfg_read_blob(FW_CFG_ID, &rev, 0, sizeof(rev)); > > >> + err = fw_cfg_read_blob(FW_CFG_ID, &rev, 0, sizeof(rev)); > > >> + if (err < 0) > > >> + goto err_probe; > > >> + > > >> fw_cfg_rev = le32_to_cpu(rev); > > >> err = sysfs_create_file(fw_cfg_top_ko, &fw_cfg_rev_attr.attr); > > >> if (err) > > > > > > I think that this is the only case where it's not doing the right thing right now in > > > that it shows 0 as the revision to the users. Is it worth failing probe > > > here? We could just skip the attribute, could we not? > > > > I think it's best to fail the probe if we have a read failure at that time. > > I'd rather we just dropped this attribute completely. > Why is it there? > Does any userspace actually need it? > Gabriel? I'd recommend keeping it: `cat /sys/firmware/qemu_fw_cfg/rev` is how you can easily tell if, e.g., dma is supported :) If you end up with a '0' there, it's because locking ACPI with WAIT_FOREVER failed with something other than AE_NOT_CONFIGURED, which should never happen, so we're off the reservation, having morally failed the equivalent of an assertion. Perhaps memset to something other than 0 (all-Fs, so we'd get a -1 for rev)? Thanks, --Gabriel > > > -- > > Marc-Andr? Lureau