From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932984AbeB1Pc7 (ORCPT ); Wed, 28 Feb 2018 10:32:59 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:52800 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932170AbeB1Pc4 (ORCPT ); Wed, 28 Feb 2018 10:32:56 -0500 Date: Wed, 28 Feb 2018 17:32:52 +0200 From: "Michael S. Tsirkin" To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Cc: open list , slp@redhat.com, bhe@redhat.com, somlo@cmu.edu, xiaolong.ye@intel.com Subject: Re: [PATCH v15 08/11] fw_cfg: handle fw_cfg_read_blob() error Message-ID: <20180228173014-mutt-send-email-mst@kernel.org> References: <20180215213312.29234-1-marcandre.lureau@redhat.com> <20180215213312.29234-9-marcandre.lureau@redhat.com> <20180227021150-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: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 28, 2018 at 12:49:35PM +0100, Marc-André 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-André 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-André 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? > -- > Marc-André Lureau