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| author | Thomas Gleixner <tglx@linutronix.de> | 2016-03-18 08:35:29 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-03-18 14:51:06 +0100 |
| commit | f508a5ba7a4570418df6cfd68fe663ffdef2be63 (patch) | |
| tree | 2434d09f8cfadd8022470464529dae59483a214a | |
| parent | 7834c10313fb823e538f2772be78edcdeed2e6e3 (diff) | |
| download | linux-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.c | 6 |
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; |