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authorThomas Gleixner <tglx@linutronix.de>2016-03-18 08:35:29 +0100
committerThomas Gleixner <tglx@linutronix.de>2016-03-18 14:51:06 +0100
commitf508a5ba7a4570418df6cfd68fe663ffdef2be63 (patch)
tree2434d09f8cfadd8022470464529dae59483a214a
parent7834c10313fb823e538f2772be78edcdeed2e6e3 (diff)
downloadlinux-f508a5ba7a4570418df6cfd68fe663ffdef2be63.tar.bz2
x86/tsc: Prevent NULL pointer deref in calibrate_delay_is_known()
The topology_core_cpumask is used to find a neighbour cpu in calibrate_delay_is_known(). It might not be allocated at the first invocation of that function on the boot cpu, when CONFIG_CPUMASK_OFFSTACK is set. The mask is allocated later in native_smp_prepare_cpus. As a consequence the underlying find_next_bit() call dereferences a NULL pointer. Add a proper check to prevent this. Fixes: c25323c07345 "x86/tsc: Use topology functions" Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Josh Boyer <jwboyer@fedoraproject.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1603180843270.3978@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--arch/x86/kernel/tsc.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 5e19d2587cc5..c9c4c7ce3eb2 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1306,11 +1306,15 @@ void __init tsc_init(void)
unsigned long calibrate_delay_is_known(void)
{
int sibling, cpu = smp_processor_id();
+ struct cpumask *mask = topology_core_cpumask(cpu);
if (!tsc_disabled && !cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC))
return 0;
- sibling = cpumask_any_but(topology_core_cpumask(cpu), cpu);
+ if (!mask)
+ return 0;
+
+ sibling = cpumask_any_but(mask, cpu);
if (sibling < nr_cpu_ids)
return cpu_data(sibling).loops_per_jiffy;
return 0;