qemu/util/systemd.c
Eric Blake 474a6e64f2 tools: Fix use of fcntl(F_SETFD) during socket activation
Blindly setting FD_CLOEXEC without a read-modify-write will
inadvertently clear any other intentionally-set bits, such as a
proposed new bit for designating a fd that must behave in 32-bit mode.
However, we cannot use our wrapper qemu_set_cloexec(), because that
wrapper intentionally abort()s on failure, whereas the probe here
intentionally tolerates failure to deal with incorrect socket
activation gracefully.  Instead, fix the code to do the proper
read-modify-write.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200420175309.75894-3-eblake@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
2020-05-04 14:54:35 -05:00

80 lines
1.9 KiB
C

/*
* systemd socket activation support
*
* Copyright 2017 Red Hat, Inc. and/or its affiliates
*
* Authors:
* Richard W.M. Jones <rjones@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qemu/systemd.h"
#include "qemu/cutils.h"
#include "qemu/error-report.h"
#ifndef _WIN32
unsigned int check_socket_activation(void)
{
const char *s;
unsigned long pid;
unsigned long nr_fds;
unsigned int i;
int fd;
int f;
int err;
s = getenv("LISTEN_PID");
if (s == NULL) {
return 0;
}
err = qemu_strtoul(s, NULL, 10, &pid);
if (err) {
return 0;
}
if (pid != getpid()) {
return 0;
}
s = getenv("LISTEN_FDS");
if (s == NULL) {
return 0;
}
err = qemu_strtoul(s, NULL, 10, &nr_fds);
if (err) {
return 0;
}
assert(nr_fds <= UINT_MAX);
/* So these are not passed to any child processes we might start. */
unsetenv("LISTEN_FDS");
unsetenv("LISTEN_PID");
/* So the file descriptors don't leak into child processes. */
for (i = 0; i < nr_fds; ++i) {
fd = FIRST_SOCKET_ACTIVATION_FD + i;
f = fcntl(fd, F_GETFD);
if (f == -1 || fcntl(fd, F_SETFD, f | FD_CLOEXEC) == -1) {
/* If we cannot set FD_CLOEXEC then it probably means the file
* descriptor is invalid, so socket activation has gone wrong
* and we should exit.
*/
error_report("Socket activation failed: "
"invalid file descriptor fd = %d: %s",
fd, g_strerror(errno));
exit(EXIT_FAILURE);
}
}
return (unsigned int) nr_fds;
}
#else /* !_WIN32 */
unsigned int check_socket_activation(void)
{
return 0;
}
#endif