diff options
| author | Darren Tucker <dtucker@dtucker.net> | 2021-08-20 08:30:42 +1000 |
|---|---|---|
| committer | Darren Tucker <dtucker@dtucker.net> | 2021-08-20 08:30:42 +1000 |
| commit | 10e45654cff221ca60fd35ee069df67208fcf415 (patch) | |
| tree | aeebc10bfd44872acf4072e4d418046ccd9a74d1 | |
| parent | 464ba22f1e38d25402e5ec79a9b8d34a32df5a3f (diff) | |
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.
| -rw-r--r-- | openbsd-compat/bsd-pselect.c | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/openbsd-compat/bsd-pselect.c b/openbsd-compat/bsd-pselect.c index da34b41d..983427aa 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; } |