[tip:x86/urgent] x86/apic: Fix parsing of the 'lapic' cmdline option

From: tip-bot for Mathias Krause
Date: Wed Feb 20 2013 - 09:00:53 EST


Commit-ID: 27cf929845b10043f2257693c7d179a9e0b1980e
Gitweb: http://git.kernel.org/tip/27cf929845b10043f2257693c7d179a9e0b1980e
Author: Mathias Krause <minipli@xxxxxxxxxxxxxx>
AuthorDate: Tue, 19 Feb 2013 20:47:07 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 20 Feb 2013 11:24:36 +0100

x86/apic: Fix parsing of the 'lapic' cmdline option

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().

Reported-by: PaX Team <pageexec@xxxxxxxxxxx>
Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1361303227-13174-1-git-send-email-minipli@xxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # v3.8
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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 a5b4dce..904611b 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;
}
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