From aff6fe17f52815e6ebdbf82b69f3edf669808eb6 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Wed, 13 Jun 2018 15:48:25 -0700 Subject: [PATCH] x86/speculation/l1tf: Make sure the first page is always reserved commit 10a70416e1f067f6c4efda6ffd8ea96002ac4223 upstream The L1TF workaround doesn't make any attempt to mitigate speculate accesses to the first physical page for zeroed PTEs. Normally it only contains some data from the early real mode BIOS. It's not entirely clear that the first page is reserved in all configurations, so add an extra reservation call to make sure it is really reserved. In most configurations (e.g. with the standard reservations) it's likely a nop. Signed-off-by: Andi Kleen Signed-off-by: Thomas Gleixner Reviewed-by: Josh Poimboeuf Acked-by: Dave Hansen Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/setup.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index efbcf5283520..dcb00acb6583 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -852,6 +852,12 @@ void __init setup_arch(char **cmdline_p) memblock_reserve(__pa_symbol(_text), (unsigned long)__bss_stop - (unsigned long)_text); + /* + * Make sure page 0 is always reserved because on systems with + * L1TF its contents can be leaked to user processes. + */ + memblock_reserve(0, PAGE_SIZE); + early_reserve_initrd(); /* -- 2.20.1