From cf40361ede6cf9dc09349e4c049dc0d166ca2d8b Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Tue, 11 Sep 2018 11:18:12 -0700 Subject: [PATCH] x86/efi: Load fixmap GDT in efi_call_phys_epilog() before setting %cr3 Commit eeb89e2bb1ac ("x86/efi: Load fixmap GDT in efi_call_phys_epilog()") moved loading the fixmap in efi_call_phys_epilog() after load_cr3() since it was assumed to be more logical. Turns out this is incorrect: In efi_call_phys_prolog(), the gdt with its physical address is loaded first, and when the %cr3 is reloaded in _epilog from initial_page_table to swapper_pg_dir again the gdt is no longer mapped. This results in a triple fault if an interrupt occurs after load_cr3() and before load_fixmap_gdt(0). Calling load_fixmap_gdt(0) first restores the execution order prior to commit eeb89e2bb1ac and fixes the problem. Fixes: eeb89e2bb1ac ("x86/efi: Load fixmap GDT in efi_call_phys_epilog()") Signed-off-by: Guenter Roeck Signed-off-by: Thomas Gleixner Acked-by: Linus Torvalds Cc: Ard Biesheuvel Cc: linux-efi@vger.kernel.org Cc: Andy Lutomirski Cc: Joerg Roedel Link: https://lkml.kernel.org/r/1536689892-21538-1-git-send-email-linux@roeck-us.net --- arch/x86/platform/efi/efi_32.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c index 05ca14222463..9959657127f4 100644 --- a/arch/x86/platform/efi/efi_32.c +++ b/arch/x86/platform/efi/efi_32.c @@ -85,10 +85,9 @@ pgd_t * __init efi_call_phys_prolog(void) void __init efi_call_phys_epilog(pgd_t *save_pgd) { + load_fixmap_gdt(0); load_cr3(save_pgd); __flush_tlb_all(); - - load_fixmap_gdt(0); } void __init efi_runtime_update_mappings(void) -- 2.39.5