linux-kernel - [PATCH 4.9 19/66] arm64: cpufeature: __this_cpu_has

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Date:   Tue, 17 Apr 2018 17:58:52 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        James Morse <james.morse@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Greg Hackmann <ghackmann@...gle.com>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 4.9 19/66] arm64: cpufeature: __this_cpu_has_cap() shouldnt stop early

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

------------------

From: Mark Rutland <mark.rutland@....com>


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