On Fri, Jul 13, 2018 at 03:09:07PM +0200, Marc-André Lureau wrote:
> There are variants of qemu_create_pidfile() in qemu-pr-helper and
> qemu-ga. Let's have a common implementation in libqemuutil.
>
> The code is based from pr-helper write_pidfile(), but allows the
> caller to deal with error reporting and behaviour.
>
> Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> ---
> include/qemu/osdep.h | 3 ++-
> os-posix.c | 24 -------------------
> os-win32.c | 25 --------------------
> qga/main.c | 54 ++++++++-----------------------------------
> scsi/qemu-pr-helper.c | 40 ++++----------------------------
> util/oslib-posix.c | 33 ++++++++++++++++++++++++++
> util/oslib-win32.c | 27 ++++++++++++++++++++++
> vl.c | 4 ++--
> 8 files changed, 79 insertions(+), 131 deletions(-)
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index 13b6f8d776..da1d4a3201 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -88,6 +88,39 @@ int qemu_daemon(int nochdir, int noclose)
> return daemon(nochdir, noclose);
> }
>
> +bool qemu_write_pidfile(const char *pidfile, Error **errp)
> +{
> + int pidfd;
> + char pidstr[32];
> +
> + pidfd = qemu_open(pidfile, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
> + if (pidfd == -1) {
> + error_setg_errno(errp, errno, "Cannot open pid file");
> + return false;
> + }
> +
> + if (lockf(pidfd, F_TLOCK, 0)) {
> + error_setg_errno(errp, errno, "Cannot lock pid file");
> + goto fail;
> + }
> + if (ftruncate(pidfd, 0)) {
> + error_setg_errno(errp, errno, "Failed to truncate pid file");
> + goto fail;
> + }
> +
> + snprintf(pidstr, sizeof(pidstr), "%d\n", getpid());
> + if (write(pidfd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
> + error_setg(errp, "Failed to write pid file");
> + goto fail;
> + }
> + return true;
> +
> +fail:
> + unlink(pidfile);
Danger, Will Robinson !
We can get to this fail: label if we were unable to lockf() the
pidfile. ie someone else owns the pidfile, and we've now unlinked
the pidfile they own.
> + close(pidfd);
> + return false;
> +}
> +
> void *qemu_oom_check(void *ptr)
> {
> if (ptr == NULL) {
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
