From ff18c65862ff8453aa0fb51aafd3482caf2f9ec6 Mon Sep 17 00:00:00 2001
From: "Todd C. Miller" <Todd.Miller@courtesan.com>
Date: Sat, 12 Oct 2013 05:39:02 -0600
Subject: [PATCH] Use SOCK_STREAM for socketpair, not SOCK_DGRAM so we get
 consistent semantics when the other end closes.  This should make the
 conversion to poll() less problematic.

---
 src/exec.c     | 34 ++++++++++++++--------------------
 src/exec_pty.c | 15 ++++++++++-----
 2 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/src/exec.c b/src/exec.c
index f70ad77f8..2d966ca28 100644
--- a/src/exec.c
+++ b/src/exec.c
@@ -255,7 +255,7 @@ sudo_execute(struct command_details *details, struct command_status *cstat)
      * We communicate with the child over a bi-directional pair of sockets.
      * Parent sends signal info to child and child sends back wait status.
      */
-    if (socketpair(PF_UNIX, SOCK_DGRAM, 0, sv) == -1)
+    if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1)
 	fatal(_("unable to create sockets"));
 
     /*
@@ -374,12 +374,7 @@ sudo_execute(struct command_details *details, struct command_status *cstat)
 		if (n == -1) {
 		    if (errno == EINTR)
 			continue;
-		    /*
-		     * If not logging I/O we may receive ECONNRESET when
-		     * the command is executed and sv is closed.
-		     * It is safe to ignore this.
-		     */
-		    if (log_io && errno != EAGAIN) {
+		    if (errno != EAGAIN) {
 			cstat->type = CMD_ERRNO;
 			cstat->val = errno;
 			break;
@@ -391,8 +386,16 @@ sudo_execute(struct command_details *details, struct command_status *cstat)
 		    sudo_debug_printf(SUDO_DEBUG_ERROR,
 			"failed to read child status: %s",
 			n ? "short read" : "EOF");
-		    /* XXX - should set cstat */
-		    break;
+		    /*
+		     * If not logging I/O we may get EOF when the command is
+		     * executed and sv is closed.  It is safe to ignore this.
+		     */
+		    if (log_io || n != 0) {
+			/* XXX - need new CMD_ type for monitor errors. */
+			cstat->type = CMD_ERRNO;
+			cstat->val = n ? EIO : ECONNRESET;
+			break;
+		    }
 		}
 	    }
 	    if (cstat->type == CMD_PID) {
@@ -505,17 +508,8 @@ dispatch_signals(int sv[2], pid_t child, int log_io, struct command_status *csta
 	    do {
 		pid = waitpid(child, &status, WUNTRACED|WNOHANG);
 	    } while (pid == -1 && errno == EINTR);
-	    if (pid == child) {
-		if (log_io) {
-		    /*
-		     * On BSD we get ECONNRESET on sv[0] if monitor dies
-		     * and select() will return with sv[0] readable.
-		     * On Linux that doesn't appear to happen so if the
-		     * monitor dies, shut down the socketpair to force a
-		     * select() notification.
-		     */
-		    (void) shutdown(sv[0], SHUT_WR);
-		} else if (WIFSTOPPED(status)) {
+	    if (pid == child && !log_io) {
+		if (WIFSTOPPED(status)) {
 		    /*
 		     * Save the controlling terminal's process group
 		     * so we can restore it after we resume, if needed.
diff --git a/src/exec_pty.c b/src/exec_pty.c
index f8940e5be..286fe4e5b 100644
--- a/src/exec_pty.c
+++ b/src/exec_pty.c
@@ -1170,11 +1170,16 @@ exec_monitor(struct command_details *details, int backchannel)
 
 	    /* read command from backchannel, should be a signal */
 	    n = recv(backchannel, &cstmp, sizeof(cstmp), 0);
-	    if (n == -1) {
-		if (errno == EINTR)
-		    continue;
-		warning(_("error reading from socketpair"));
-		goto done;
+	    if (n != sizeof(cstmp)) {
+		if (n == -1) {
+		    if (errno == EINTR)
+			continue;
+		    warning(_("error reading from socketpair"));
+		    goto done;
+		} else {
+		    /* /* short read or EOF, parent process died? */
+		    goto done;
+		}
 	    }
 	    if (cstmp.type != CMD_SIGNO) {
 		warningx(_("unexpected reply type on backchannel: %d"),
-- 
2.49.0