From 10a70416e1f067f6c4efda6ffd8ea96002ac4223 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 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 --- 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 2f86d883dd95..74b4472ba0a6 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -823,6 +823,12 @@ 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(); /* -- GitLab