seccomp_user_notif.2: Add BUGS section describing SECCOMP_IOCTL_NOTIF_RECV bug

Tycho Andersen confirmed that this issue is present.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man2/seccomp_user_notif.2 b/man2/seccomp_user_notif.2
index 099d9b6c8530904246200fac264b019ab6d216b3..0c11abcd4adf195e7df37c812e20daf69fdb46c6 100644 (file)
--- a/man2/seccomp_user_notif.2
+++ b/man2/seccomp_user_notif.2
@@ -349,6 +349,8 @@ was being generated.
 .\" Is this expected behavior? It seems to me rather
 .\" desirable that SECCOMP_IOCTL_NOTIF_RECV should give an error
 .\" if the target process has terminated.
+.\"
+.\" For now, this behavior is documented in BUGS.
 .TP
 .B SECCOMP_IOCTL_NOTIF_ID_VALID
 This operation can be used to check that a notification ID
@@ -562,6 +564,14 @@ these interfaces indicate that the file descriptor is readable.
 .\" Interestingly, after the event had been received, the file
 .\" descriptor indicates as writable (verified from the source
 .\" code and by experiment). How is this useful?
+.SH BUGS
+If a
+.BR SECCOMP_IOCTL_NOTIF_RECV
+.BR ioctl (2)
+operation is performed after the target process terminates, then the
+.BR ioctl (2)
+call simply blocks (rather than returning an error to indicate that the
+target process no longer exists).
 .SH EXAMPLES
 The (somewhat contrived) program shown below demonstrates the use of
 the interfaces described in this page.