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qemu-ga: guest-shutdown: use only async-signal-safe functions

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POSIX mandates[1] that a child process of a multi-thread program uses
only async-signal-safe functions before exec(). We consider qemu-ga
to be multi-thread, because it uses glib.

However, qmp_guest_shutdown() uses functions that are not
async-signal-safe. Fix it the following way:

- fclose() -> reopen_fd_to_null()
- execl() -> execle()
- exit() -> _exit()
- drop slog() usage (which is not safe)

  [1] http://pubs.opengroup.org/onlinepubs/009695399/functions/fork.html

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
This commit is contained in:
Luiz Capitulino 2012-05-14 15:25:20 -03:00 committed by Michael Roth
parent d5dd3498eb
commit 3674838cd0
2 changed files with 8 additions and 12 deletions
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3
qapi-schema-guest.json
View File

@ -126,8 +126,7 @@
# @guest-shutdown:
#
# Initiate guest-activated shutdown. Note: this is an asynchronous
# shutdown request, with no guaruntee of successful shutdown. Errors
# will be logged to guest's syslog.
# shutdown request, with no guarantee of successful shutdown.
#
# @mode: #optional "halt", "powerdown" (default), or "reboot"
#

17
qga/commands-posix.c
View File

@ -37,8 +37,8 @@
void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err)
{
const char *shutdown_flag;
int ret, status;
pid_t rpid, pid;
int status;
slog("guest-shutdown called, mode: %s", mode);
if (!has_mode || strcmp(mode, "powerdown") == 0) {
@ -57,16 +57,13 @@ void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err)
if (pid == 0) {
/* child, start the shutdown */
setsid();
fclose(stdin);
fclose(stdout);
fclose(stderr);
reopen_fd_to_null(0);
reopen_fd_to_null(1);
reopen_fd_to_null(2);
ret = execl("/sbin/shutdown", "shutdown", shutdown_flag, "+0",
"hypervisor initiated shutdown", (char*)NULL);
if (ret) {
slog("guest-shutdown failed: %s", strerror(errno));
}
exit(!!ret);
execle("/sbin/shutdown", "shutdown", shutdown_flag, "+0",
"hypervisor initiated shutdown", (char*)NULL, environ);
_exit(EXIT_FAILURE);
} else if (pid < 0) {
goto exit_err;
}