Re: [PATCH] selftests/proc: Fix proc-pid-vm for vsyscall=xonly.

On 6/16/22 3:10 PM, Dylan Hatch wrote:

This test would erroneously fail the /proc/$PID/maps case if vsyscall=xonly since the existing probe of the vsyscall page only succeeds if the process has read permissions. Fix this by checking for either no vsyscall mapping OR an execute-only vsyscall mapping in the case were probing the vsyscall page segfaults.

Does this fix include skipping the test with a clear message that says why test is skipped?

Signed-off-by: Dylan Hatch dylanbhatch@google.com

tools/testing/selftests/proc/proc-pid-vm.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/proc/proc-pid-vm.c b/tools/testing/selftests/proc/proc-pid-vm.c index 28604c9f805c..5ca85520131f 100644 --- a/tools/testing/selftests/proc/proc-pid-vm.c +++ b/tools/testing/selftests/proc/proc-pid-vm.c @@ -213,9 +213,12 @@ static int make_exe(const uint8_t *payload, size_t len) static bool g_vsyscall = false; -static const char str_vsyscall[] = +static const char str_vsyscall_rx[] = "ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n"; +static const char str_vsyscall_x[] = +"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n";

• #ifdef __x86_64__ static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___) {

@@ -261,6 +264,7 @@ int main(void) int exec_fd; vsyscall();

• const char *str_vsyscall = g_vsyscall ? str_vsyscall_rx : str_vsyscall_x;

atexit(ate); @@ -314,7 +318,8 @@ int main(void) /* Test /proc/$PID/maps */ {

• const size_t len = strlen(buf0) + (g_vsyscall ? strlen(str_vsyscall) : 0);
  

• const size_t len_buf0 = strlen(buf0);
  

• const size_t len_vsys = strlen(str_vsyscall);
  

  char buf[256]; ssize_t rv; int fd;

@@ -325,11 +330,16 @@ int main(void) return 1; } rv = read(fd, buf, sizeof(buf));

• assert(rv == len);
  

• assert(memcmp(buf, buf0, strlen(buf0)) == 0);
  

  if (g_vsyscall) {

• 	assert(memcmp(buf + strlen(buf0), str_vsyscall, strlen(str_vsyscall)) == 0);
  

• 	assert(rv == len_buf0 + len_vsys);
  

• } else {
  

• 	/* If vsyscall isn't readable, it's either x-only or not mapped at all */
  

• 	assert(rv == len_buf0 + len_vsys || rv == len_buf0);
  

  }

• assert(memcmp(buf, buf0, len_buf0) == 0);
  

• /* Check for vsyscall mapping if buf is long enough */
  

• if (rv == len_buf0 + len_vsys)
  

• 	assert(memcmp(buf + len_buf0, str_vsyscall, len_vsys) == 0);
  

  }

/* Test /proc/$PID/smaps */

The change looks good to me. Doesn't look like it skips the test though?

thanks, -- Shuah