Author: kib
Date: Wed Oct 28 22:12:47 2020
New Revision: 367120
URL: https://svnweb.freebsd.org/changeset/base/367120
Log:
Check for process group change in tty_wait_background().
The calling process's process group can change between PROC_UNLOCK(p)
and PGRP_LOCK(pg) in tty_wait_background(), e.g. by a setpgid() call
from another process. If that happens, the signal is not sent to the
calling process, even if the prior checks determine that one should be
sent. Re-check that the process group hasn't changed after acquiring
the pgrp lock, and if it has, redo the checks.
PR: 250701
Submitted by: Jakub Piecuch <j.piecuc...@gmail.com>
MFC after: 2 weeks
Modified:
head/sys/kern/tty.c
Modified: head/sys/kern/tty.c
==============================================================================
--- head/sys/kern/tty.c Wed Oct 28 21:18:04 2020 (r367119)
+++ head/sys/kern/tty.c Wed Oct 28 22:12:47 2020 (r367120)
@@ -474,6 +474,19 @@ tty_wait_background(struct tty *tp, struct thread *td,
sig = 0;
}
PGRP_LOCK(pg);
+
+ /*
+ * pg may no longer be our process group.
+ * Re-check after locking process group.
+ */
+ PROC_LOCK(p);
+ if (p->p_pgrp != pg) {
+ PROC_UNLOCK(p);
+ PGRP_UNLOCK(pg);
+ continue;
+ }
+
+ PROC_UNLOCK(p);
pgsignal(pg, ksi.ksi_signo, 1, &ksi);
PGRP_UNLOCK(pg);
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