[PATCH v4 4/8] firmware: add call to LSM hook before firmware sysfs fallback

[Mimi Zohar]

Add an LSM hook prior to allowing firmware sysfs fallback loading.

Signed-off-by: Mimi Zohar <zo...@linux.vnet.ibm.com>
Cc: Luis R. Rodriguez <mcg...@suse.com>
Cc: David Howells <dhowe...@redhat.com>
Cc: Kees Cook <keesc...@chromium.org>

Changelog v4:
- call new LSM security_kernel_arg hook

Changelog v2:
- call security_kernel_read_blob()
- rename the READING_FIRMWARE_FALLBACK kernel_read_file_id enumeration to
READING_FIRMWARE_FALLBACK_SYSFS.
---
 drivers/base/firmware_loader/fallback.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/base/firmware_loader/fallback.c 
b/drivers/base/firmware_loader/fallback.c
index 358354148dec..2443bda81631 100644
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -651,6 +651,8 @@ static bool fw_force_sysfs_fallback(unsigned int opt_flags)
 
 static bool fw_run_sysfs_fallback(unsigned int opt_flags)
 {
+       int ret;
+
        if (fw_fallback_config.ignore_sysfs_fallback) {
                pr_info_once("Ignoring firmware sysfs fallback due to sysctl 
knob\n");
                return false;
@@ -659,6 +661,11 @@ static bool fw_run_sysfs_fallback(unsigned int opt_flags)
        if ((opt_flags & FW_OPT_NOFALLBACK))
                return false;
 
+       /* Also permit LSMs and IMA to fail firmware sysfs fallback */
+       ret = security_kernel_load_data(LOADING_FIRMWARE);
+       if (ret < 0)
+               return ret;
+
        return fw_force_sysfs_fallback(opt_flags);
 }
 
-- 
2.7.5