From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752248AbeB1Ltj (ORCPT ); Wed, 28 Feb 2018 06:49:39 -0500 Received: from mail-wr0-f194.google.com ([209.85.128.194]:41116 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752147AbeB1Lti (ORCPT ); Wed, 28 Feb 2018 06:49:38 -0500 X-Google-Smtp-Source: AG47ELu87JonoRvbWwd5JpH10dwo+9XMKjgdUDdtwIDqNWJWPOU+yXiMkD4tCCjPtdSoyR/rZDhzQdCBrfOQ5D7ov1g= MIME-Version: 1.0 In-Reply-To: <20180227021150-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> From: =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= Date: Wed, 28 Feb 2018 12:49:35 +0100 Message-ID: Subject: Re: [PATCH v15 08/11] fw_cfg: handle fw_cfg_read_blob() error To: "Michael S. Tsirkin" Cc: open list , slp@redhat.com, bhe@redhat.com, somlo@cmu.edu, xiaolong.ye@intel.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id w1SBnijR032030 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. -- Marc-André Lureau