From: Roy Marples <roy@marples.name>
Date: Wed, 10 Jun 2020 15:32:04 +0000 (+0100)
Subject: privsep: Fix a shutdown race
X-Git-Tag: v9.1.2~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=536f64cabf24ea7ada1fa0c0fd5e59b5960391f3;p=thirdparty%2Fdhcpcd.git

privsep: Fix a shutdown race

Only test a successful stop IPC command.
By the time we shutdown the socket to be extra nice, the
process we sent stop to could have already exited, therefore
we can discard any error.
---

diff --git a/src/privsep-root.c b/src/privsep-root.c
index efafc20a..46daeb07 100644
--- a/src/privsep-root.c
+++ b/src/privsep-root.c
@@ -480,7 +480,6 @@ ps_root_recvmsgcb(void *arg, struct ps_msghdr *psm, struct msghdr *msg)
 			shutdown(psp->psp_fd, SHUT_RDWR);
 			close(psp->psp_fd);
 			psp->psp_fd = -1;
-			ps_dostop(ctx, &psp->psp_pid, &psp->psp_fd);
 			ps_freeprocess(psp);
 		}
 		return 0;
diff --git a/src/privsep.c b/src/privsep.c
index b2f3b309..d05681aa 100644
--- a/src/privsep.c
+++ b/src/privsep.c
@@ -401,17 +401,16 @@ ps_dostop(struct dhcpcd_ctx *ctx, pid_t *pid, int *fd)
 	int err = 0;
 
 #ifdef PRIVSEP_DEBUG
-	logdebugx("%s: pid %d fd %d", __func__, *pid, *fd);
+	logdebugx("%s: pid=%d fd=%d", __func__, *pid, *fd);
 #endif
 
 	if (*fd != -1) {
 		eloop_event_delete(ctx->eloop, *fd);
-		if (ps_sendcmd(ctx, *fd, PS_STOP, 0, NULL, 0) == -1 ||
-		    shutdown(*fd, SHUT_RDWR) == -1)
-		{
+		if (ps_sendcmd(ctx, *fd, PS_STOP, 0, NULL, 0) == -1) {
 			logerr(__func__);
 			err = -1;
 		}
+		(void)shutdown(*fd, SHUT_RDWR);
 		close(*fd);
 		*fd = -1;
 	}