From 72cd652b73dd77df6f26bd450e804ee29232669f Mon Sep 17 00:00:00 2001 From: Athira Rajeev Date: Mon, 5 Sep 2022 19:49:28 +0530 Subject: [PATCH] perf affinity: Fix out of bound access to "sched_cpus" mask 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: <<>> ./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': msec cpu-clock context-switches cpu-migrations page-faults cycles instructions branches branch-misses 0.001192373 seconds time elapsed <<>> Reported-by: Nageswara R Sastry Signed-off-by: Athira Jajeev Tested-by: Arnaldo Carvalho de Melo Tested-by: Nageswara R Sastry Cc: Jiri Olsa Cc: Kajol Jain Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org Link: https://lore.kernel.org/r/20220905141929.7171-1-atrajeev@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo --- 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); /*