Current code fails to check for an error case when reading events
from final event log to calculate offsets.  Check the error case,
and break early because all subsequent calls will also fail.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
 drivers/firmware/efi/libstub/tpm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
index f194e43f00ad..8e04aaf428d0 100644
--- a/drivers/firmware/efi/libstub/tpm.c
+++ b/drivers/firmware/efi/libstub/tpm.c
@@ -124,6 +124,9 @@ static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_loca
 			event_size = __calc_tpm2_event_size(header,
 						   (void *)(long)log_location,
 						   false);
+			/* If calc fails this is a malformed log */
+			if (!event_size)
+				break;
 			final_events_size += event_size;
 			i--;
 		}
-- 
2.43.0