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Tsirkin" To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Cc: linux-kernel@vger.kernel.org, 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: <20180227021150-mutt-send-email-mst@kernel.org> References: <20180215213312.29234-1-marcandre.lureau@redhat.com> <20180215213312.29234-9-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180215213312.29234-9-marcandre.lureau@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Tue, 27 Feb 2018 00:20:14 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Tue, 27 Feb 2018 00:20:14 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mst@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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? > @@ -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? > -- > 2.16.1.73.g5832b7e9f2