diff options
| author | Michal Koutný <mkoutny@suse.com> | 2023-03-06 20:31:44 +0100 |
|---|---|---|
| committer | Dave Hansen <dave.hansen@linux.intel.com> | 2023-03-22 10:42:47 -0700 |
| commit | a3f547addcaa10df5a226526bc9e2d9a94542344 (patch) | |
| tree | 94654c004b82a932ea4a5348fd545d6008e13182 | |
| parent | cbebd68f59f03633469f3ecf9bea99cd6cce3854 (diff) | |
| download | linux-a3f547addcaa10df5a226526bc9e2d9a94542344.tar.gz | |
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 <mkoutny@suse.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20230306193144.24605-1-mkoutny%40suse.com
| -rw-r--r-- | arch/x86/mm/cpu_entry_area.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c index 7316a822425992..e91500a8096394 100644 --- a/arch/x86/mm/cpu_entry_area.c +++ b/arch/x86/mm/cpu_entry_area.c @@ -10,6 +10,7 @@ #include <asm/fixmap.h> #include <asm/desc.h> #include <asm/kasan.h> +#include <asm/setup.h> 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) */ |