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djm pushed a commit to branch master
in repository openssh.

commit a612b93de5d86e955bfb6e24278f621118eea500
Author: djm@openbsd.org <djm@openbsd.org>
Date: Thu Oct 12 02:12:53 2023 +0000

upstream: mask SIGINT/TERM/QUIT/HUP before checking quit_pending

and use ppoll() to unmask them in the mainloop. Avoids race condition between
signaling ssh to exit and polling. bz3531; ok dtucker

OpenBSD-Commit-ID: 5c14e1aabcddedb95cdf972283d9c0d5083229e7
---
clientloop.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/clientloop.c b/clientloop.c
index e8131637..8e323a60 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.399 2023/10/11 22:42:26 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.400 2023/10/12 02:12:53 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -681,7 +681,7 @@ obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout,
static void
client_wait_until_can_do_something(struct ssh *ssh, struct pollfd **pfdp,
u_int *npfd_allocp, u_int *npfd_activep, int channel_did_enqueue,
- int *conn_in_readyp, int *conn_out_readyp)
+ sigset_t *sigsetp, int *conn_in_readyp, int *conn_out_readyp)
{
struct timespec timeout;
int ret, oready;
@@ -728,7 +728,7 @@ client_wait_until_can_do_something(struct ssh *ssh, struct pollfd **pfdp,
ssh_packet_get_rekey_timeout(ssh));
}

- ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), NULL);
+ ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp);

if (ret == -1) {
/*
@@ -1448,6 +1448,7 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
int channel_did_enqueue = 0, r, len;
u_int64_t ibytes, obytes;
int conn_in_ready, conn_out_ready;
+ sigset_t bsigset, osigset;

debug("Entering interactive session.");
session_ident = ssh2_chan_id;
@@ -1533,6 +1534,13 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,

schedule_server_alive_check();

+ if (sigemptyset(&bsigset) == -1 ||
+ sigaddset(&bsigset, SIGHUP) == -1 ||
+ sigaddset(&bsigset, SIGINT) == -1 ||
+ sigaddset(&bsigset, SIGQUIT) == -1 ||
+ sigaddset(&bsigset, SIGTERM) == -1)
+ error_f("bsigset setup: %s", strerror(errno));
+
/* Main loop of the client for the interactive session mode. */
while (!quit_pending) {
channel_did_enqueue = 0;
@@ -1564,17 +1572,20 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
* message about it to the server if so.
*/
client_check_window_change(ssh);
-
- if (quit_pending)
- break;
}
/*
* Wait until we have something to do (something becomes
* available on one of the descriptors).
*/
+ if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1)
+ error_f("bsigset sigprocmask: %s", strerror(errno));
+ if (quit_pending)
+ break;
client_wait_until_can_do_something(ssh, &pfd, &npfd_alloc,
- &npfd_active, channel_did_enqueue,
+ &npfd_active, channel_did_enqueue, &osigset,
&conn_in_ready, &conn_out_ready);
+ if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1)
+ error_f("osigset sigprocmask: %s", strerror(errno));

if (quit_pending)
break;

--
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