From 10e45654cff221ca60fd35ee069df67208fcf415 Mon Sep 17 00:00:00 2001
From: Darren Tucker <dtucker@dtucker.net>
Date: Fri, 20 Aug 2021 08:30:42 +1000
Subject: [PATCH] Fix race in pselect replacement code.
On the second and subsequent calls to pselect the notify_pipe was not
added to the select readset, opening up a race that om G. Christensen
discovered on multiprocessor Solaris <=9 systems.
Also reinitialize notify_pipe if the pid changes. This will prevent a
parent and child from using the same FD, although this is not an issue
in the current structure it might be in future.
---
openbsd-compat/bsd-pselect.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/openbsd-compat/bsd-pselect.c b/openbsd-compat/bsd-pselect.c
index da34b41d8..983427aae 100644
--- a/openbsd-compat/bsd-pselect.c
+++ b/openbsd-compat/bsd-pselect.c
@@ -73,6 +73,7 @@ notify_setup_fd(int *fd)
* we write to this pipe if a SIGCHLD is caught in order to avoid
* the race between select() and child_terminated
*/
+static pid_t notify_pid;
static int notify_pipe[2];
static void
notify_setup(void)
@@ -81,6 +82,15 @@ notify_setup(void)
if (initialized)
return;
+ if (notify_pid == 0)
+ debug3_f("initializing");
+ else {
+ debug3_f("pid changed, reinitializing");
+ if (notify_pipe[0] != -1)
+ close(notify_pipe[0]);
+ if (notify_pipe[1] != -1)
+ close(notify_pipe[1]);
+ }
if (pipe(notify_pipe) == -1) {
error("pipe(notify_pipe) failed %s", strerror(errno));
} else if (notify_setup_fd(¬ify_pipe[0]) == -1 ||
@@ -91,6 +101,9 @@ notify_setup(void)
} else {
set_nonblock(notify_pipe[0]);
set_nonblock(notify_pipe[1]);
+ notify_pid = getpid();
+ debug3_f("pid %d saved %d pipe0 %d pipe1 %d", getpid(),
+ notify_pid, notify_pipe[0], notify_pipe[1]);
initialized = 1;
return;
}
@@ -159,15 +172,16 @@ pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
if (sig == SIGKILL || sig == SIGSTOP || sigismember(mask, sig))
continue;
if (sigaction(sig, NULL, &sa) == 0 &&
- sa.sa_handler != SIG_IGN && sa.sa_handler != SIG_DFL &&
- sa.sa_handler != sig_handler) {
+ sa.sa_handler != SIG_IGN && sa.sa_handler != SIG_DFL) {
+ unmasked = 1;
+ if (sa.sa_handler == sig_handler)
+ continue;
sa.sa_handler = sig_handler;
if (sigaction(sig, &sa, &osa) == 0) {
debug3_f("installing signal handler for %s, "
"previous %p", strsignal(sig),
osa.sa_handler);
saved_sighandler[sig] = osa.sa_handler;
- unmasked = 1;
}
}
}
@@ -183,7 +197,8 @@ pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
saved_errno = errno;
sigprocmask(SIG_SETMASK, &osig, NULL);
- notify_done(readfds);
+ if (unmasked)
+ notify_done(readfds);
errno = saved_errno;
return ret;
}