This is a note to let you know that I've just added the patch titled
[Variant 2/Spectre-v2] arm64: cpufeature: __this_cpu_has_cap() shouldn't stop early
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: arm64-cpufeature-__this_cpu_has_cap-shouldn-t-stop-early.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Tue Feb 13 17:25:10 CET 2018
From: James Morse james.morse@arm.com Date: Mon, 15 Jan 2018 19:38:54 +0000 Subject: [Variant 2/Spectre-v2] arm64: cpufeature: __this_cpu_has_cap() shouldn't stop early
From: James Morse james.morse@arm.com
Commit edf298cfce47 upstream.
this_cpu_has_cap() tests caps->desc not caps->matches, so it stops walking the list when it finds a 'silent' feature, instead of walking to the end of the list.
Prior to v4.6's 644c2ae198412 ("arm64: cpufeature: Test 'matches' pointer to find the end of the list") we always tested desc to find the end of a capability list. This was changed for dubious things like PAN_NOT_UAO. v4.7's e3661b128e53e ("arm64: Allow a capability to be checked on single CPU") added this_cpu_has_cap() using the old desc style test.
CC: Suzuki K Poulose suzuki.poulose@arm.com Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com Acked-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: James Morse james.morse@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/cpufeature.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1173,9 +1173,8 @@ static bool __this_cpu_has_cap(const str if (WARN_ON(preemptible())) return false;
- for (caps = cap_array; caps->desc; caps++) + for (caps = cap_array; caps->matches; caps++) if (caps->capability == cap && - caps->matches && caps->matches(caps, SCOPE_LOCAL_CPU)) return true; return false;
Patches currently in stable-queue which might be from james.morse@arm.com are
queue-4.15/arm64-kpti-fix-the-interaction-between-asid-switching-and-software-pan.patch queue-4.15/arm64-cpufeature-__this_cpu_has_cap-shouldn-t-stop-early.patch