From: Ard Biesheuvel <ardb@kernel.org>
Date: Sun, 8 Mar 2020 09:08:45 +0100
Subject: efi/libstub/x86: Deal with exit() boot service returning
Patch-mainline: v5.7-rc1
Git-commit: f3fa0efce2e765f24356b70bd0786f290d84328c
References: jsc#SLE-16407

Even though it is uncommon, there are cases where the Exit() EFI boot
service might return, e.g., when we were booted via the EFI handover
protocol from OVMF and the kernel image was specified on the command
line, in which case Exit() attempts to terminate the boot manager,
which is not an EFI application itself.

So let's drop into an infinite loop instead of randomly executing code
that isn't expecting it.

Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
[ardb: put 'hlt' in deadloop]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200303080648.21427-1-ardb@kernel.org
Link: https://lore.kernel.org/r/20200308080859.21568-15-ardb@kernel.org
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 drivers/firmware/efi/libstub/x86-stub.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -344,7 +344,8 @@ static void setup_graphics(struct boot_p
 static void __noreturn efi_exit(efi_handle_t handle, efi_status_t status)
 {
 	efi_bs_call(exit, handle, status, 0, NULL);
-	unreachable();
+	for(;;)
+		asm("hlt");
 }
 
 void startup_32(struct boot_params *boot_params);