arm64: cpufeature: __this_cpu_has_cap() shouldn't stop early

From: James Morse <james.morse@arm.com>

commit edf298cfce47ab7279d03b5203ae2ef3a58e49db 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: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]
Tested-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 5056fc597ae9614d1ee26d3416af3977ed445134..cf000fd694fafc89c4839725db39724a302cccc5 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1024,9 +1024,8 @@ static bool __this_cpu_has_cap(const struct arm64_cpu_capabilities *cap_array,
        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;