From: Michal Koutný Date: Mon, 6 Mar 2023 19:31:44 +0000 (+0100) Subject: x86/mm: Do not shuffle CPU entry areas without KASLR X-Git-Tag: v6.6.7~3220^2~2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a3f547addcaa10df5a226526bc9e2d9a94542344;p=platform%2Fkernel%2Flinux-starfive.git x86/mm: Do not shuffle CPU entry areas without KASLR The commit 97e3d26b5e5f ("x86/mm: Randomize per-cpu entry area") fixed an omission of KASLR on CPU entry areas. It doesn't take into account KASLR switches though, which may result in unintended non-determinism when a user wants to avoid it (e.g. debugging, benchmarking). Generate only a single combination of CPU entry areas offsets -- the linear array that existed prior randomization when KASLR is turned off. Since we have 3f148f331814 ("x86/kasan: Map shadow for percpu pages on demand") and followups, we can use the more relaxed guard kasrl_enabled() (in contrast to kaslr_memory_enabled()). Fixes: 97e3d26b5e5f ("x86/mm: Randomize per-cpu entry area") Signed-off-by: Michal Koutný Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20230306193144.24605-1-mkoutny%40suse.com --- diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c index 7316a82..e91500a 100644 --- a/arch/x86/mm/cpu_entry_area.c +++ b/arch/x86/mm/cpu_entry_area.c @@ -10,6 +10,7 @@ #include #include #include +#include static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage); @@ -29,6 +30,12 @@ static __init void init_cea_offsets(void) unsigned int max_cea; unsigned int i, j; + if (!kaslr_enabled()) { + for_each_possible_cpu(i) + per_cpu(_cea_offset, i) = i; + return; + } + max_cea = (CPU_ENTRY_AREA_MAP_SIZE - PAGE_SIZE) / CPU_ENTRY_AREA_SIZE; /* O(sodding terrible) */