[v4.9.y,11/42] arm64: cpufeature: __this_cpu_has_cap() shouldn't stop early

Message ID 20180412111138.40990-12-mark.rutland@arm.com
State New
Headers show
  • arm64 spectre patches
Related show

Commit Message

Mark Rutland April 12, 2018, 11:11 a.m.
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]

 arch/arm64/kernel/cpufeature.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)



diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 5056fc597ae9..cf000fd694fa 100644
--- 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;