[PATCH v2] efi_loader: Don't stop EFI subsystem init if installing TCG2 fails

Ilias Apalodimas ilias.apalodimas at linaro.org
Tue May 11 23:03:41 CEST 2021

Up to now we are stopping the EFI subsystem if a TPMv2 exists but the
protocol fails to install.  Now that we've switched the config to 'default
y' the sandbox TPM fails, since it doesn't support all the required
capabilities of the protocol.

Not installing the protocol is not catastrophic.  If the protocol fails
to install the PCRs will never be extended to the expected values, so
some other entity later in the boot flow will eventually figure it out
and take the necessary actions.

While at it fix a corner case were the user can see an invalid error
message when the protocol failed to install.  We do have a tcg2_uninit()
which we call when the protocol installation fails.  There are cases though
that this might be called before the configuration table is installed (e.g
probing the TPM for capabilities failed).  In that case the user will see
"Failed to delete final events config table".  So stop printing it since it's
not an actual failure , simply because the config table was never installed 
in the first place.

In order to stop printing it make efi_init_event_log() and create_final_event()
cleanup themselves and only call tcg2_uninit() when the protocol installation 

Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
changes since v1:
- stop printing a warning when tcg2_uninit was called before installing
  the final events config table
 lib/efi_loader/efi_tcg2.c | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index 8f8a26e7b7ae..31343e47678f 100644
--- a/lib/efi_loader/efi_tcg2.c
+++ b/lib/efi_loader/efi_tcg2.c
@@ -999,6 +999,11 @@ static efi_status_t create_final_event(void)
 	event_log.final_pos = sizeof(*final_event);
 	ret = efi_install_configuration_table(&efi_guid_final_events,
+	if (ret != EFI_SUCCESS) {
+		efi_free_pool(event_log.final_buffer);
+		event_log.final_buffer = NULL;
+	}
 	return ret;
@@ -1047,15 +1052,22 @@ static efi_status_t efi_init_event_log(void)
 	ret = create_specid_event(dev, (void *)((uintptr_t)event_log.buffer + sizeof(*event_header)),
 	if (ret != EFI_SUCCESS)
-		goto out;
+		goto free_pool;
 	put_unaligned_le32(spec_event_size, &event_header->event_size);
 	event_log.pos = spec_event_size + sizeof(*event_header);
 	event_log.last_event_size = event_log.pos;
 	ret = create_final_event();
+	if (ret != EFI_SUCCESS)
+		goto free_pool;
 	return ret;
+	efi_free_pool(event_log.buffer);
+	event_log.buffer = NULL;
+	return ret;
@@ -1112,19 +1124,30 @@ efi_status_t efi_tcg2_register(void)
 		goto fail;
 	ret = efi_append_scrtm_version(dev);
-	if (ret != EFI_SUCCESS)
+	if (ret != EFI_SUCCESS) {
+		tcg2_uninit();
 		goto fail;
+	}
 	ret = efi_add_protocol(efi_root, &efi_guid_tcg2_protocol,
 			       (void *)&efi_tcg2_protocol);
 	if (ret != EFI_SUCCESS) {
-		log_err("Cannot install EFI_TCG2_PROTOCOL\n");
+		tcg2_uninit();
 		goto fail;
 	return ret;
-	tcg2_uninit();
-	return ret;
+	log_err("Cannot install EFI_TCG2_PROTOCOL\n");
+	/*
+	 * Return EFI_SUCCESS and don't stop the EFI subsystem.
+	 * That's done for 2 reasons
+	 * - If the protocol is not installed the PCRs won't be extended.  So
+	 *   someone later in the boot flow will notice that and take the
+	 *   necessary actions.
+	 * - The TPM sandbox is limited and we won't be able to run any efi
+	 *   related tests with TCG2 enabled
+	 */
+	return EFI_SUCCESS;

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