qemu/util/event_notifier-posix.c
Frediano Ziglio 105e1023a8 event_notifier: avoid dandling file descriptor in event_notifier_cleanup
If rfd is equal to wfd the file descriptor is closed but
rfd will still have the closed value.
The EventNotifier structure should not be used again after calling
event_notifier_cleanup or should be initialized again but make
sure to not have dandling file descriptors around.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20191023122652.2999-2-fziglio@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2019-10-24 19:26:52 +02:00

125 lines
2.4 KiB
C

/*
* event notifier support
*
* Copyright Red Hat, Inc. 2010
*
* Authors:
* Michael S. Tsirkin <mst@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-common.h"
#include "qemu/cutils.h"
#include "qemu/event_notifier.h"
#include "qemu/main-loop.h"
#ifdef CONFIG_EVENTFD
#include <sys/eventfd.h>
#endif
#ifdef CONFIG_EVENTFD
/*
* Initialize @e with existing file descriptor @fd.
* @fd must be a genuine eventfd object, emulation with pipe won't do.
*/
void event_notifier_init_fd(EventNotifier *e, int fd)
{
e->rfd = fd;
e->wfd = fd;
}
#endif
int event_notifier_init(EventNotifier *e, int active)
{
int fds[2];
int ret;
#ifdef CONFIG_EVENTFD
ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
#else
ret = -1;
errno = ENOSYS;
#endif
if (ret >= 0) {
e->rfd = e->wfd = ret;
} else {
if (errno != ENOSYS) {
return -errno;
}
if (qemu_pipe(fds) < 0) {
return -errno;
}
ret = fcntl_setfl(fds[0], O_NONBLOCK);
if (ret < 0) {
ret = -errno;
goto fail;
}
ret = fcntl_setfl(fds[1], O_NONBLOCK);
if (ret < 0) {
ret = -errno;
goto fail;
}
e->rfd = fds[0];
e->wfd = fds[1];
}
if (active) {
event_notifier_set(e);
}
return 0;
fail:
close(fds[0]);
close(fds[1]);
return ret;
}
void event_notifier_cleanup(EventNotifier *e)
{
if (e->rfd != e->wfd) {
close(e->rfd);
}
e->rfd = -1;
close(e->wfd);
e->wfd = -1;
}
int event_notifier_get_fd(const EventNotifier *e)
{
return e->rfd;
}
int event_notifier_set(EventNotifier *e)
{
static const uint64_t value = 1;
ssize_t ret;
do {
ret = write(e->wfd, &value, sizeof(value));
} while (ret < 0 && errno == EINTR);
/* EAGAIN is fine, a read must be pending. */
if (ret < 0 && errno != EAGAIN) {
return -errno;
}
return 0;
}
int event_notifier_test_and_clear(EventNotifier *e)
{
int value;
ssize_t len;
char buffer[512];
/* Drain the notify pipe. For eventfd, only 8 bytes will be read. */
value = 0;
do {
len = read(e->rfd, buffer, sizeof(buffer));
value |= (len > 0);
} while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
return value;
}