efi/libstub: Avoid returning uninitialized data from setup_graphics()

Currently, setup_graphics() ignores the return value of efi_setup_gop(). As
AllocatePool() does not zero out memory, the screen information table will
contain uninitialized data in this case.

We should free the screen information table if efi_setup_gop() returns an
error code.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/20200426194946.112768-1-xypron.glpk@gmx.de
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 99a5cde7c2d8fc52e914e4c7f2e38a8dc91c4f58..48161b1dd098f2694f8d5baf02403b6291928ea8 100644 (file)
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -60,7 +60,11 @@ static struct screen_info *setup_graphics(void)
                si = alloc_screen_info();
                if (!si)
                        return NULL;
-               efi_setup_gop(si, &gop_proto, size);
+               status = efi_setup_gop(si, &gop_proto, size);
+               if (status != EFI_SUCCESS) {
+                       free_screen_info(si);
+                       return NULL;
+               }
        }
        return si;
 }