pe: Fix PF in GRUB after memattrs call

The call to update_mem_attrs() takes an aligned pointer within an
allocated region but passes the entire size of the allocated region. The
result is that Shim may remove execute permission from some pages
belonging to GRUB causing a page fault upon returning from the LoadImage
call.

Signed-off-by: Ross Lagerwall <[email protected]>

Author: rosslagerwall

pe.c

@@ -717,7 +717,7 @@ handle_image (void *data, unsigned int datasize,
 	dprint(L"Loading 0x%llx bytes at 0x%llx\n",
 	       (unsigned long long)context.ImageSize,
 	       (unsigned long long)(uintptr_t)buffer);
-	update_mem_attrs((uintptr_t)buffer, alloc_size, MEM_ATTR_R|MEM_ATTR_W,
+	update_mem_attrs((uintptr_t)buffer, context.ImageSize, MEM_ATTR_R|MEM_ATTR_W,
 			 MEM_ATTR_X);
 
 	CopyMem(buffer, data, context.SizeOfHeaders);