Re: [libvirt] [PATCH 5/5] qemu: add support for sending QEMU stdout/stderr to virtlogd

Currently the QEMU stdout/stderr streams are written directly to a regular file (eg /var/log/libvirt/qemu/$GUEST.log). While those can be rotated by logrotate (using copytruncate option) this is not very efficient. It also leaves open a window of opportunity for a compromised/broken QEMU to DOS the host filesystem by writing lots of text to stdout/stderr. This makes it possible to connect the stdout/stderr file handles to a pipe that is provided by virtlogd. The virtlogd daemon will read from this pipe and write data to the log file, performing file rotation whenever a pre-determined size limit is reached. Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- cfg.mk | 2 +- src/qemu/libvirtd_qemu.aug | 1 + src/qemu/qemu.conf | 15 +++++++++++++ src/qemu/qemu_conf.c | 18 ++++++++++++++++ src/qemu/qemu_conf.h | 1 + src/qemu/qemu_domain.c | 43 +++++++++++++++++++++++++++++++------- src/qemu/qemu_process.c | 42 +++++++++++++++++++++---------------- src/qemu/test_libvirtd_qemu.aug.in | 1 + 8 files changed, 96 insertions(+), 27 deletions(-)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index f744419..e72ca20 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -4774,7 +4774,10 @@ int qemuProcessStart(virConnectPtr conn, qemuDomainObjCheckTaint(driver, vm, logfile); - if ((pos = lseek(logfile, 0, SEEK_END)) < 0) + /* When using logd, the logfile FD is a pipe which is + * not seekable... */ + if (!cfg->stdioLogD && + (pos = lseek(logfile, 0, SEEK_END)) < 0) VIR_WARN("Unable to seek to end of logfile: %s", virStrerror(errno, ebuf, sizeof(ebuf)));