On Tue, Nov 03, 2015 at 16:04:24 +0000, Daniel Berrange wrote:
> 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@xxxxxxxxxx>
> ---
> 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)));
This will break the code that is in place to read the qemu log file in
case of a early qemu startup failure so that we can report a semi-useful
error message.
Additionally in case where you don't use QMP and qemu does not support
chardev info retrieval, this will also break the lookup of the PTYs for
serials/parallels/channels. As a solution here I'd rather see that we
drop support for such old qemus finally and not have to care about it
any more.
We probably need a set of APIs here, that will allow you to mark a place
in the logfile and a second API that will allow to retrieve the data
between the marker and the end.
Peter
Attachment:
signature.asc
Description: Digital signature
-- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list