Hi On Tue, Feb 27, 2018 at 1:20 AM, Michael S. Tsirkin <[email protected]> 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 <[email protected]> >> --- >> 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
