On 05/09/22 10:24 am, Athira Rajeev wrote:
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':
<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>
---
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..a1dd37347abc 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 / __BITS_PER_LONG) >= (cpu_set_size / 8)))
return;
+
a->changed = true;
set_bit(cpu, a->sched_cpus);
/*
--
Thanks and Regards
R.Nageswara Sastry
