git: 8cf005884326 - stable/15 - syslogd: reap pipe children on config reload

The branch stable/15 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=8cf005884326fd15324bc484867c0a947607cb45

commit 8cf005884326fd15324bc484867c0a947607cb45
Author:     Baptiste Daroussin <bapt@FreeBSD.org>
AuthorDate: 2026-09-02 08:51:42 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2026-09-09 08:34:33 +0000

    syslogd: reap pipe children on config reload
    
    On SIGHUP reload, closelogfiles() frees each F_PIPE filed even when its
    pipe process is still running.  close_filed() sets f_type to F_UNUSED
    before the check, so the condition f_type != F_PIPE is always true and
    the filed is freed while its process descriptor is still on the dead
    queue and registered in the kqueue.  When the child later exits, the
    NOTE_EXIT handler dereferences the freed filed (use-after-free) and
    never closes the process descriptor, leaving the pipe child as a
    persistent zombie.
    
    Capture whether the filed is a pipe with an active process descriptor
    before calling close_filed(), and defer the free in that case so the
    NOTE_EXIT handler can reap the child and free the filed.
    
    Reviewed by:    markj
    Fixes:  95381c0139d6 (syslogd: Use process descriptors)
    Differential Revision:  https://reviews.freebsd.org/D59319
    
    (cherry picked from commit 1a669b66ddb4748c24116e32dcb51eabaf4859ed)
---
 usr.sbin/syslogd/syslogd.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/usr.sbin/syslogd/syslogd.c b/usr.sbin/syslogd/syslogd.c
index 8589f3ae9a12..13626eff44cb 100644
--- a/usr.sbin/syslogd/syslogd.c
+++ b/usr.sbin/syslogd/syslogd.c
@@ -2547,6 +2547,7 @@ void
 closelogfiles(void)
 {
 	struct filed *f;
+	bool defer_free;
 
 	while (!STAILQ_EMPTY(&fhead)) {
 		f = STAILQ_FIRST(&fhead);
@@ -2556,6 +2557,13 @@ closelogfiles(void)
 		if (f->f_prevcount)
 			fprintlog_successive(f, 0);
 
+		/*
+		 * If a piped process is running, then defer the filed
+		 * cleanup until it exits.  close_filed() below sets
+		 * f_type to F_UNUSED, so capture this before calling it.
+		 */
+		defer_free = (f->f_type == F_PIPE && f->f_procdesc != -1);
+
 		switch (f->f_type) {
 		case F_FILE:
 		case F_FORW:
@@ -2583,11 +2591,7 @@ closelogfiles(void)
 			free(f->f_prop_filter);
 		}
 
-		/*
-		 * If a piped process is running, then defer the filed
-		 * cleanup until it exits.
-		 */
-		if (f->f_type != F_PIPE || f->f_procdesc == -1)
+		if (!defer_free)
 			free(f);
 	}
 }