x86/mm: Do not shuffle CPU entry areas without KASLR

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commit a3f547addc upstream.

The commit 97e3d26b5e ("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 3f148f3318 ("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: 97e3d26b5e ("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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Michal Koutný 2023-03-06 20:31:44 +01:00 • committed by Greg Kroah-Hartman

parent 11222d9f5a

commit 7730c3102f

1 changed files with 7 additions and 0 deletions

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arch/x86/mm/cpu_entry_area.c

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