Em Mon, Sep 05, 2022 at 07:49:28PM +0530, Athira Rajeev escreveu: > The affinity code in "affinity_set" function access array > named "sched_cpus". The size for this array is allocated in > affinity_setup function which is nothing but value from > get_cpu_set_size. This is used to contain the cpumask value > for each cpu. While setting bit for each cpu, it calls > "set_bit" function which access index in sched_cpus array. > If we provide a command-line option to -C which is more than > the number of CPU's present in the system, the set_bit could > access an array member which is out-of the array size. This > is because currently, there is no boundary check for the CPU. > This will result in seg fault:
Thanks, tested, reproduced the problem before, and the fix after, applied. - Arnaldo > <<>> > ./perf stat -C 12323431 ls > Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS > Segmentation fault (core dumped) > <<>> > > Fix this by adding boundary check for the array. > > After the fix from powerpc system: > > <<>> > ./perf stat -C 12323431 ls 1>out > Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS > > Performance counter stats for 'CPU(s) 12323431': > > <not supported> msec cpu-clock > <not supported> context-switches > <not supported> cpu-migrations > <not supported> page-faults > <not supported> cycles > <not supported> instructions > <not supported> branches > <not supported> branch-misses > > 0.001192373 seconds time elapsed > <<>> > > Reported-by: Nageswara Sastry <rnsas...@linux.ibm.com> > Tested-by: Nageswara Sastry <rnsas...@linux.ibm.com> > Signed-off-by: Athira Rajeev <atraj...@linux.vnet.ibm.com> > --- > Changelog: > From v1 -> v2: > Addressed review comment from Jiri Olsa by changing condition > check to directly use "cpu_set_size * 8" for comparing with the > cpu number. > > tools/perf/util/affinity.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/tools/perf/util/affinity.c b/tools/perf/util/affinity.c > index 4d216c0dc425..4ee96b3c755b 100644 > --- a/tools/perf/util/affinity.c > +++ b/tools/perf/util/affinity.c > @@ -49,8 +49,14 @@ void affinity__set(struct affinity *a, int cpu) > { > int cpu_set_size = get_cpu_set_size(); > > - if (cpu == -1) > + /* > + * Return: > + * - if cpu is -1 > + * - restrict out of bound access to sched_cpus > + */ > + if (cpu == -1 || ((cpu >= (cpu_set_size * 8)))) > return; > + > a->changed = true; > set_bit(cpu, a->sched_cpus); > /* > -- > 2.35.1 -- - Arnaldo