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console: exit mainloop on SIGTERM

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This allows cleanly exiting a console session without control sequences.

Relates to https://github.com/lxc/lxd/pull/4001 .

Note that the existence of a signal handler now doesn't guarantee that ts->node
is allocated. Instead, ts->node will now only be added to if stdinfd is a tty.
New checks need to take that into account.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Christian Brauner 2017-11-12 17:51:11 +01:00
parent 0519b5cce7
commit 1349e92e4d
No known key found for this signature in database
GPG Key ID: 7B3C391EFEA93624
1 changed files with 43 additions and 20 deletions
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61
src/lxc/console.c
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@ -110,21 +110,30 @@ void lxc_console_sigwinch(int sig)
int lxc_console_cb_signal_fd(int fd, uint32_t events, void *cbdata, int lxc_console_cb_signal_fd(int fd, uint32_t events, void *cbdata,
struct lxc_epoll_descr *descr) struct lxc_epoll_descr *descr)
{ {
ssize_t ret;
struct signalfd_siginfo siginfo; struct signalfd_siginfo siginfo;
struct lxc_tty_state *ts = cbdata; struct lxc_tty_state *ts = cbdata;
ssize_t ret = read(fd, &siginfo, sizeof(siginfo)); ret = read(fd, &siginfo, sizeof(siginfo));
if (ret < 0 || (size_t)ret < sizeof(siginfo)) { if (ret < 0 || (size_t)ret < sizeof(siginfo)) {
ERROR("Failed to read signal info"); ERROR("Failed to read signal info");
return -1; return -1;
} }
if (siginfo.ssi_signo == SIGTERM) {
DEBUG("Received SIGTERM. Detaching from the console");
return 1;
}
if (siginfo.ssi_signo == SIGWINCH)
lxc_console_winch(ts); lxc_console_winch(ts);
return 0; return 0;
} }
struct lxc_tty_state *lxc_console_signal_init(int srcfd, int dstfd) struct lxc_tty_state *lxc_console_signal_init(int srcfd, int dstfd)
{ {
int ret;
bool istty; bool istty;
sigset_t mask; sigset_t mask;
struct lxc_tty_state *ts; struct lxc_tty_state *ts;
@ -138,35 +147,45 @@ struct lxc_tty_state *lxc_console_signal_init(int srcfd, int dstfd)
ts->masterfd = dstfd; ts->masterfd = dstfd;
ts->sigfd = -1; ts->sigfd = -1;
sigemptyset(&mask);
istty = isatty(srcfd) == 1; istty = isatty(srcfd) == 1;
if (!istty) { if (!istty) {
INFO("fd %d does not refer to a tty device", srcfd); INFO("fd %d does not refer to a tty device", srcfd);
return ts; } else {
} /* Add tty to list to be scanned at SIGWINCH time. */
/* add tty to list to be scanned at SIGWINCH time */
lxc_list_add_elem(&ts->node, ts); lxc_list_add_elem(&ts->node, ts);
lxc_list_add_tail(&lxc_ttys, &ts->node); lxc_list_add_tail(&lxc_ttys, &ts->node);
sigemptyset(&mask);
sigaddset(&mask, SIGWINCH); sigaddset(&mask, SIGWINCH);
if (sigprocmask(SIG_BLOCK, &mask, &ts->oldmask)) { }
SYSERROR("Failed to block SIGWINCH signal");
ts->sigfd = -1; /* Exit the mainloop cleanly on SIGTERM. */
lxc_list_del(&ts->node); sigaddset(&mask, SIGTERM);
return ts;
ret = sigprocmask(SIG_BLOCK, &mask, &ts->oldmask);
if (ret < 0) {
WARN("Failed to block signals");
goto on_error;
} }
ts->sigfd = signalfd(-1, &mask, 0); ts->sigfd = signalfd(-1, &mask, 0);
if (ts->sigfd < 0) { if (ts->sigfd < 0) {
SYSERROR("Failed to create signal fd"); WARN("Failed to create signal fd");
sigprocmask(SIG_SETMASK, &ts->oldmask, NULL); sigprocmask(SIG_SETMASK, &ts->oldmask, NULL);
ts->sigfd = -1; goto on_error;
lxc_list_del(&ts->node);
return ts;
} }
DEBUG("Process %d created signal fd %d", getpid(), ts->sigfd); DEBUG("Created signal fd %d", ts->sigfd);
return ts;
on_error:
ERROR("Failed to create signal fd");
if (ts->sigfd >= 0) {
close(ts->sigfd);
ts->sigfd = -1;
}
if (istty)
lxc_list_del(&ts->node);
return ts; return ts;
} }
@ -174,10 +193,14 @@ void lxc_console_signal_fini(struct lxc_tty_state *ts)
{ {
if (ts->sigfd >= 0) { if (ts->sigfd >= 0) {
close(ts->sigfd); close(ts->sigfd);
lxc_list_del(&ts->node);
sigprocmask(SIG_SETMASK, &ts->oldmask, NULL); if (sigprocmask(SIG_SETMASK, &ts->oldmask, NULL) < 0)
WARN("%s - Failed to restore signal mask", strerror(errno));
} }
if (isatty(ts->stdinfd))
lxc_list_del(&ts->node);
free(ts); free(ts);
} }