Hi,
On 01-05-18 16:36, Mimi Zohar wrote:
[Cc'ing linux-security]
On Sun, 2018-04-29 at 11:35 +0200, Hans de Goede wrote:
[...]
diff --git a/drivers/base/firmware_loader/fallback_efi.c b/drivers/base/firmware_loader/fallback_efi.c
new file mode 100644
index 000000000000..82ba82f48a79
--- /dev/null
+++ b/drivers/base/firmware_loader/fallback_efi.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi_embedded_fw.h>
+#include <linux/property.h>
+#include <linux/security.h>
+#include <linux/vmalloc.h>
+
+#include "fallback.h"
+#include "firmware.h"
+
+int fw_get_efi_embedded_fw(struct device *dev, struct fw_priv *fw_priv,
+ enum fw_opt *opt_flags, int ret)
+{
+ enum kernel_read_file_id id = READING_FIRMWARE;
Please define a new kernel_read_file_id for this (eg.
READING_FIRMWARE_EFI_EMBEDDED).
Are you sure, I wonder how useful it is to add a new
kernel_read_file_id every time a new way to get firmware
comes up?
I especially wonder about the sense in adding a new id
given that the quite old FIRMWARE_PREALLOC_BUFFER is
still not supported / checked properly by the security code.
Anyways I can add a new id if you want me to, what about
when fw_get_efi_embedded_fw is reading into a driver allocated
buffer, do you want a separate EADING_FIRMWARE_EFI_EMBEDDED_PREALLOC_BUFFER
for that ?
+ size_t size, max = INT_MAX;
+ int rc;
+
+ if (!dev)
+ return ret;
+
+ if (!device_property_read_bool(dev, "efi-embedded-firmware"))
+ return ret;
Instead of calling security_kernel_post_read_file(), either in
device_property_read_bool() or here call security_kernel_read_file().
The pre read call is for deciding whether to allow this call
independent of the firmware being loaded, whereas the post security
call is currently being used by IMA-appraisal for verifying a
signature. There might be other LSMs using the post hook as well. As
there is no kernel signature associated with this firmware, use the
security pre read_file hook.
Only the pre hook? I believe the post-hook should still be called too,
right? So that we've hashes of all loaded firmwares in the IMA core.
Regards,
Hans
thanks,
Mimi
+
+ *opt_flags |= FW_OPT_NO_WARN | FW_OPT_NOCACHE | FW_OPT_NOFALLBACK;
+
+ /* Already populated data member means we're loading into a buffer */
+ if (fw_priv->data) {
+ id = READING_FIRMWARE_PREALLOC_BUFFER;
+ max = fw_priv->allocated_size;
+ }
+
+ rc = efi_get_embedded_fw(fw_priv->fw_name, &fw_priv->data, &size, max);
+ if (rc) {
+ dev_warn(dev, "Firmware %s not in EFI\n", fw_priv->fw_name);
+ return ret;
+ }
+
+ rc = security_kernel_post_read_file(NULL, fw_priv->data, size, id);
+ if (rc) {
+ if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
+ vfree(fw_priv->data);
+ fw_priv->data = NULL;
+ }
+ return rc;
+ }
+
+ dev_dbg(dev, "using efi-embedded fw %s\n", fw_priv->fw_name);
+ fw_priv->size = size;
+ fw_state_done(fw_priv);
+ return 0;
+}
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