[glibc] tst-pidfd.c: UNSUPPORTED if we get EPERM on valid pidfd_getfd call

[Mark Wielaard <mark@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=325ba824b0611e14e96b38dbc486acf255f9e568

commit 325ba824b0611e14e96b38dbc486acf255f9e568
Author: Mark Wielaard <mark@klomp.org>
Date:   Sun Jun 26 22:17:17 2022 +0200

    tst-pidfd.c: UNSUPPORTED if we get EPERM on valid pidfd_getfd call
    
    pidfd_getfd can fail for a valid pidfd with errno EPERM for various
    reasons in a restricted environment. Use FAIL_UNSUPPORTED in that case.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>

Diff:
---
 sysdeps/unix/sysv/linux/tst-pidfd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sysdeps/unix/sysv/linux/tst-pidfd.c b/sysdeps/unix/sysv/linux/tst-pidfd.c
index d93b6faa6f..037af22290 100644
--- a/sysdeps/unix/sysv/linux/tst-pidfd.c
+++ b/sysdeps/unix/sysv/linux/tst-pidfd.c
@@ -142,6 +142,13 @@ do_test (void)
     xrecvfrom (sockets[0], &remote_fd, sizeof (remote_fd), 0, NULL, 0);
 
     int fd = pidfd_getfd (pidfd, remote_fd, 0);
+    /* pidfd_getfd may fail with EPERM if the process does not have
+       PTRACE_MODE_ATTACH_REALCREDS permissions. This means the call
+       may be denied if the process doesn't have CAP_SYS_PTRACE or
+       if a LSM security_ptrace_access_check denies access.  */
+    if (fd == -1 && errno == EPERM)
+      FAIL_UNSUPPORTED ("don't have permission to use pidfd_getfd on pidfd, "
+			"skipping test");
     TEST_VERIFY (fd > 0);
 
     char *path = xasprintf ("/proc/%d/fd/%d", pid, remote_fd);