Re: [libvirt] [PATCH] Don't use O_TRUNC when opening QEMU logfiles

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; SELinux wants all log files opened with O_APPEND. When running non-root though, libvirtd likes to use O_TRUNC to avoid log files growing in size indefinitely. Instead of using O_TRUNC though, we can use O_APPEND and then call ftruncate() which keeps SELinux happier. Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- src/qemu/qemu_domain.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index 0ae30b7..e67c247 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -1446,12 +1446,22 @@ qemuDomainOpenLogHelper(struct qemud_driver *driver, { char *logfile; int fd = -1; + bool trunc = false; if (virAsprintf(&logfile, "%s/%s.log", driver->logDir, vm->def->name) < 0) { virReportOOMError(); return -1; } + /* To make SELinux happy we always need to open in append mode. + * So we fake O_TRUNC by calling ftruncate after open instead + */ + if (oflags & O_TRUNC) { + oflags &= ~O_TRUNC; + oflags |= O_APPEND; + trunc = true; + } + if ((fd = open(logfile, oflags, mode)) < 0) { virReportSystemError(errno, _("failed to create logfile %s"), logfile); @@ -1463,6 +1473,13 @@ qemuDomainOpenLogHelper(struct qemud_driver *driver, VIR_FORCE_CLOSE(fd); goto cleanup; } + if (trunc && + ftruncate(fd, 0) < 0) { + virReportSystemError(errno, _("failed to truncate %s"), + logfile); + VIR_FORCE_CLOSE(fd); + goto cleanup; + }