[PATCH 4.9 19/66] arm64: cpufeature: __this_cpu_has_cap() shouldnt stop early

From: Greg Kroah-Hartman
Date: Tue Apr 17 2018 - 12:29:12 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Mark Rutland <mark.rutland@xxxxxxx>

From: James Morse <james.morse@xxxxxxx>

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@xxxxxxx>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> [v4.9 backport]
Tested-by: Greg Hackmann <ghackmann@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
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
@@ -1024,9 +1024,8 @@ 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;