Messages in this thread Patch in this message | | | Date | Fri, 18 Mar 2016 06:54:58 -0700 | From | tip-bot for Thomas Gleixner <> | Subject | [tip:x86/urgent] x86/tsc: Prevent NULL pointer deref in calibrate_delay_is_known() |
| |
Commit-ID: f508a5ba7a4570418df6cfd68fe663ffdef2be63 Gitweb: http://git.kernel.org/tip/f508a5ba7a4570418df6cfd68fe663ffdef2be63 Author: Thomas Gleixner <tglx@linutronix.de> AuthorDate: Fri, 18 Mar 2016 08:35:29 +0100 Committer: Thomas Gleixner <tglx@linutronix.de> 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@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>
--- 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;
| |