[PATCH 1/2] efi: loader: in-place patch the runtime services on ExitBootServices

[Ahmad Fatoum <a.fatoum@barebox.org>]

ExitBootServices() repoints systab->runtime at a separate table with the
detached runtime services. If an EFI application caches RT, it may end
up calling into the stale boot-time runtime services object.

Fix this by keeping the systab->runtime pointer the same and do a
"deep copy" by rewriting the object including its callbacks instead.

Cc: Johannes Schauer Marin Rodrigues <josch@debian.org>
Fixes: 699145f1cb22 ("efi: runtime: add runtime service support after ExitBootServices")
Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
 efi/loader/boot.c      | 5 ++++-
 efi/loader/runtime.c   | 2 +-
 efi/loader/watchdog.c  | 4 ++--
 efi/runtime/services.c | 3 ++-
 include/efi/loader.h   | 2 +-
 5 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/efi/loader/boot.c b/efi/loader/boot.c
index 2d98c95b5c34..ddfbf33bff69 100644
--- a/efi/loader/boot.c
+++ b/efi/loader/boot.c
@@ -3879,6 +3879,8 @@ static struct efi_boot_services efi_boot_services = {
 
 static __efi_runtime_data u16 firmware_vendor[] = L"barebox";
 
+static __efi_runtime_data struct efi_runtime_services efi_runtime_services;
+
 __efi_runtime_data struct efi_system_table systab = {
 	.hdr = {
 		.signature = EFI_SYSTEM_TABLE_SIGNATURE,
@@ -3925,8 +3927,9 @@ efi_status_t efi_initialize_system_table(void)
 	systab.boottime = &efi_boot_services;
 
 	/*
-	 * This will be overwritten dynamically at detach time.
+	 * This must be overwritten dynamically at detach time.
 	 */
+	efi_runtime_services = efi_runtime_services_boot;
 	systab.runtime = &efi_runtime_services;
 
 	/* Set CRC32 field in table headers */
diff --git a/efi/loader/runtime.c b/efi/loader/runtime.c
index a8f872f23b48..329e1077889f 100644
--- a/efi/loader/runtime.c
+++ b/efi/loader/runtime.c
@@ -293,7 +293,7 @@ static efi_status_t EFIAPI efi_set_time_boottime(struct efi_time *time)
  * the runtime services will be replaced by the detached implementation,
  * so we need not take any special consideration here.
  */
-struct efi_runtime_services efi_runtime_services = {
+struct efi_runtime_services efi_runtime_services_boot = {
 	.hdr = {
 		.signature = EFI_RUNTIME_SERVICES_SIGNATURE,
 		.revision = EFI_SPECIFICATION_VERSION,
diff --git a/efi/loader/watchdog.c b/efi/loader/watchdog.c
index a4715c149add..c29f91a0aa07 100644
--- a/efi/loader/watchdog.c
+++ b/efi/loader/watchdog.c
@@ -35,8 +35,8 @@ static void EFIAPI efi_watchdog_timer_notify(struct efi_event *event,
 	EFI_ENTRY("%p, %p", event, context);
 
 	pr_emerg("\nEFI: Watchdog timeout\n");
-	EFI_CALL_VOID(efi_runtime_services.reset_system(EFI_RESET_COLD,
-							EFI_SUCCESS, 0, NULL));
+	EFI_CALL_VOID(systab.runtime->reset_system(EFI_RESET_COLD,
+						   EFI_SUCCESS, 0, NULL));
 
 	EFI_EXIT(EFI_UNSUPPORTED);
 }
diff --git a/efi/runtime/services.c b/efi/runtime/services.c
index 5044e16c7c5c..dc4960ac4763 100644
--- a/efi/runtime/services.c
+++ b/efi/runtime/services.c
@@ -293,7 +293,8 @@ void efi_runtime_detach(struct efi_system_table *systab)
 	systab->std_err = NULL;
 	systab->boottime = NULL;
 
-	systab->runtime = &efi_runtime_services_detached;
+	/* Payloads may have cached systab->runtime, so patch it in place */
+	*systab->runtime = efi_runtime_services_detached;
 
 	/* Recalculate CRC32 */
 	efi_update_table_header_crc32(&systab->hdr);
diff --git a/include/efi/loader.h b/include/efi/loader.h
index 4dcd15854560..0ccc0a720a90 100644
--- a/include/efi/loader.h
+++ b/include/efi/loader.h
@@ -19,7 +19,7 @@ struct efi_table_hdr;
 /* Key identifying current memory map */
 extern efi_uintn_t efi_memory_map_key;
 
-extern struct efi_runtime_services efi_runtime_services;
+extern struct efi_runtime_services efi_runtime_services_boot;
 extern struct efi_system_table systab;
 
 extern struct efi_simple_text_output_protocol efi_con_out;
-- 
2.47.3