From ac610fe45491deccaab2c4ee689cbbdac117930a Mon Sep 17 00:00:00 2001

From: Javier Martinez Canillas <javierm@redhat.com>

Date: Tue, 8 Sep 2020 12:26:45 +0200

Subject: [PATCH] Fix buffer overrun due DEFAULT_LOADER length miscalculation

The DEFAULT_LOADER is a UCS-2 string and the StrLen() function returns the

number of UCS-2 encoded characters in the string. But the allocated memory

is in bytes, so only half of the needed memory to store it is allocated.

This leads to a buffer overrun when the StrCpy() function attempts to copy

the DEFAULT_LOADER to the allocated buffer.

Fixes: 354bd9b1931 ("Actually check for errors from set_second_stage()")

Reported-by: Stuart Hayes <stuart_hayes@dell.com>

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

---

 shim.c | 3 ++-

 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/shim.c b/shim.c

index 34dce25c330..82913c934f6 100644

--- a/shim.c

+++ b/shim.c

@@ -2096,8 +2096,9 @@ EFI_STATUS set_second_stage (EFI_HANDLE image_handle)

 	unsigned int i;

 	UINTN second_stage_len;

-	second_stage_len = StrLen(DEFAULT_LOADER) + 1;

+	second_stage_len = (StrLen(DEFAULT_LOADER) + 1) * sizeof(CHAR16);

 	second_stage = AllocatePool(second_stage_len);

+

 	if (!second_stage) {

 		perror(L"Could not allocate %lu bytes\n", second_stage_len);

 		return EFI_OUT_OF_RESOURCES;

-- 

2.28.0