tools/perf: Fix out of bound access to cpu mask array

tools/perf: Fix out of bound access to cpu mask array

The cpu mask init code in "record__mmap_cpu_mask_init" function access
"bits" array part of "struct mmap_cpu_mask".  The size of this array is
the value from cpu__max_cpu().cpu.  This array 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 "bits" array.

If we provide a command line option to -C which is greater 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 record -C 12341234 ls
  Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS
  Segmentation fault (core dumped)
<<>>

Debugging with gdb, points to function flow as below:

<<>>
  set_bit
  record__mmap_cpu_mask_init
  record__init_thread_default_masks
  record__init_thread_masks
  cmd_record
<<>>

Fix this by adding boundary check for the array.

After the patch:

<<>>
./perf record -C 12341234 ls
  Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS
  Failed to initialize parallel data streaming masks
<<>>

With this fix, if -C is given a non-exsiting CPU, perf
record will fail with:

<<>>
  ./perf record -C 50 ls
  Failed to initialize parallel data streaming masks
<<>>

Reported-by: Nageswara R Sastry <[email protected]>
Signed-off-by: Athira Jajeev <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Tested-by: Nageswara R Sastry <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kajol Jain <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>