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Fix malloc() deadlock in signchld handler

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This commit is contained in:
Nicolas Viennot 2016-04-26 04:05:24 -04:00
parent f28f1f99a8
commit b3c85faf3b
1 changed files with 8 additions and 7 deletions
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15
tmate-ssh-server.c
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@ -290,12 +290,20 @@ static void handle_sigchld(__unused int sig)
pid_t pid;
while ((pid = waitpid(WAIT_ANY, &status, WNOHANG)) > 0) {
/*
* It's not safe to call indirectly malloc() here, because
* of potential deadlocks with ssh_bind_accept() which also
* calls malloc(). (And we can't even block singals because
* the accept() call is blocking.
*/
#if 0
if (WIFEXITED(status))
tmate_info("Child %d exited (%d)", pid, WEXITSTATUS(status));
if (WIFSIGNALED(status))
tmate_info("Child %d killed (%d)", pid, WTERMSIG(status));
if (WIFSTOPPED(status))
tmate_info("Child %d stopped (%d)", pid, WSTOPSIG(status));
#endif
}
}
@ -309,7 +317,6 @@ static void handle_sigsegv(__unused int sig)
void tmate_ssh_server_main(struct tmate_session *session,
const char *keys_dir, int port)
{
sigset_t sigchld_set;
struct tmate_ssh_client *client = &session->ssh_client;
ssh_bind bind;
pid_t pid;
@ -317,10 +324,6 @@ void tmate_ssh_server_main(struct tmate_session *session,
signal(SIGSEGV, handle_sigsegv);
signal(SIGCHLD, handle_sigchld);
sigemptyset(&sigchld_set);
sigaddset(&sigchld_set, SIGCHLD);
sigprocmask(SIG_BLOCK, &sigchld_set, NULL);
bind = prepare_ssh(keys_dir, port);
for (;;) {
@ -332,10 +335,8 @@ void tmate_ssh_server_main(struct tmate_session *session,
if (!client->session)
tmate_fatal("Cannot initialize session");
sigprocmask(SIG_UNBLOCK, &sigchld_set, NULL);
if (ssh_bind_accept(bind, client->session) < 0)
tmate_fatal("Error accepting connection: %s", ssh_get_error(bind));
sigprocmask(SIG_BLOCK, &sigchld_set, NULL);
if (get_ip(ssh_get_fd(client->session),
client->ip_address, sizeof(client->ip_address)) < 0)