[PATCH v16 06/11] fw_cfg: handle fw_cfg_read_blob() error

Marc-André Lureau
2018-02-28T15:13:16Z

fw_cfg_read_blob() may fail, but does not return error. This may lead
to surprising behaviours, like populating zero file entries (in
register_file() or during read). 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 <marcandre.lureau@redhat.com>
---
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 0cc71d028ae3..45bfc389b226 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -77,8 +77,8 @@ 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;
@@ -91,7 +91,7 @@ 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);
@@ -102,6 +102,7 @@ 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 */
@@ -183,8 +184,9 @@ 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;
}
@@ -344,8 +346,7 @@ 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 = {
@@ -501,7 +502,11 @@ 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);

@@ -509,7 +514,10 @@ 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]);
@@ -517,6 +525,7 @@ static int fw_cfg_register_dir_entries(void)
break;
}

+end:
kfree(dir);
return ret;
}
@@ -557,7 +566,10 @@ 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)
--
2.16.1.73.g5832b7e9f2