Merge tag 'core-process-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull pidfd/waitid updates from Christian Brauner:
 "This contains two features and various tests.

  First, it adds support for waiting on process through pidfds by adding
  the P_PIDFD type to the waitid() syscall. This completes the basic
  functionality of the pidfd api (cf. [1]). In the meantime we also have
  a new adition to the userspace projects that make use of the pidfd
  api. The qt project was nice enough to send a mail pointing out that
  they have a pr up to switch to the pidfd api (cf. [2]).

  Second, this tag contains an extension to the waitid() syscall to make
  it possible to wait on the current process group in a race free manner
  (even though the actual problem is very unlikely) by specifing 0
  together with the P_PGID type. This extension traces back to a
  discussion on the glibc development mailing list.

  There are also a range of tests for the features above. Additionally,
  the test-suite which detected the pidfd-polling race we fixed in [3]
  is included in this tag"

[1] https://lwn.net/Articles/794707/
[2] https://codereview.qt-project.org/c/qt/qtbase/+/108456
[3] commit b191d6491be6 ("pidfd: fix a poll race when setting exit_state")

* tag 'core-process-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  waitid: Add support for waiting for the current process group
  tests: add pidfd poll tests
  tests: move common definitions and functions into pidfd.h
  pidfd: add pidfd_wait tests
  pidfd: add P_PIDFD to waitid()

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 534fec266a33..c4da1ef56fdf 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3678,8 +3678,11 @@ static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo, siginfo_t *info)
 
 static struct pid *pidfd_to_pid(const struct file *file)
 {
-	if (file->f_op == &pidfd_fops)
-		return file->private_data;
+	struct pid *pid;
+
+	pid = pidfd_pid(file);
+	if (!IS_ERR(pid))
+		return pid;
 
 	return tgid_pidfd_to_pid(file);
 }