On 4/26/22 6:25 AM, Colin Ian King wrote:

Currently if opening /dev/null fails to open then file pointer fp is null and further access to fp via fprintf will cause a null pointer dereference. Fix this by returning a negative error value when a null fp is detected.

Detected using cppcheck static analysis: tools/testing/selftests/resctrl/fill_buf.c:124:6: note: Assuming that condition '!fp' is not redundant if (!fp) ^ tools/testing/selftests/resctrl/fill_buf.c:126:10: note: Null pointer dereference fprintf(fp, "Sum: %d ", ret);

Fixes: a2561b12fe39 ("selftests/resctrl: Add built in benchmark") Signed-off-by: Colin Ian King colin.i.king@gmail.com

---

V2: Add cppcheck analysis information

---

tools/testing/selftests/resctrl/fill_buf.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c index 51e5cf22632f..56ccbeae0638 100644 --- a/tools/testing/selftests/resctrl/fill_buf.c +++ b/tools/testing/selftests/resctrl/fill_buf.c @@ -121,8 +121,10 @@ static int fill_cache_read(unsigned char *start_ptr, unsigned char *end_ptr, /* Consume read result so that reading memory is not optimized out. */ fp = fopen("/dev/null", "w");

• if (!fp)

• if (!fp) { perror("Unable to write to /dev/null");

• return -1;
  

• } fprintf(fp, "Sum: %d ", ret); fclose(fp);

Thank you. Applied to linux-kselftest next for Linux 5.19-rc1

thanks, -- Shuah