[PATCH] x86: apic: Fix parsing of lapic cmdline option

[Mathias Krause]

Including " lapic " in the kernel cmdline on an x86-64 kernel makes it
panic while parsing early params -- e.g. with no user visible output.

Fix this bug by ensuring arg is non-NULL before passing it to strncmp().

Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Reported-by: PaX Team <pageexec@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx	# v3.8
---
 arch/x86/kernel/apic/apic.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index b994cc8..cbf5121 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -131,7 +131,7 @@ static int __init parse_lapic(char *arg)
 {
 	if (config_enabled(CONFIG_X86_32) && !arg)
 		force_enable_local_apic = 1;
-	else if (!strncmp(arg, "notscdeadline", 13))
+	else if (arg && !strncmp(arg, "notscdeadline", 13))
 		setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
 	return 0;
 }
-- 
1.7.10.4

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