Commit-ID: f508a5ba7a4570418df6cfd68fe663ffdef2be63
Gitweb: http://git.kernel.org/tip/f508a5ba7a4570418df6cfd68fe663ffdef2be63
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Fri, 18 Mar 2016 08:35:29 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Fri, 18 Mar 2016 14:51:06 +0100
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@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1603180843270.3978@nanos
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
arch/x86/kernel/tsc.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 5e19d25..c9c4c7c 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;
--
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