On 06/15/2017 10:40 AM, Pavel Hrdina wrote: > On Thu, Jun 15, 2017 at 07:57:18AM -0400, John Ferlan wrote: >> >> >> On 06/15/2017 03:11 AM, Pavel Hrdina wrote: >>> On Tue, Jun 13, 2017 at 08:00:41PM -0400, John Ferlan wrote: >>>> >>>> >>>> On 05/29/2017 10:31 AM, Pavel Hrdina wrote: >>>>> In the case that virtlogd is used as stdio handler we pass to QEMU >>>>> only FD to a PIPE connected to virtlogd instead of the file itself. >>>>> >>>>> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1430988 >>>>> >>>>> Signed-off-by: Pavel Hrdina <phrdina@xxxxxxxxxx> >>>>> --- >>>>> >>>>> Notes: >>>>> new in v2 >>>>> >>>>> src/lxc/lxc_process.c | 6 ++--- >>>>> src/qemu/qemu_security.c | 9 +++++-- >>>>> src/security/security_apparmor.c | 7 ++++-- >>>>> src/security/security_dac.c | 54 +++++++++++++++++++++++++++++++--------- >>>>> src/security/security_driver.h | 6 +++-- >>>>> src/security/security_manager.c | 12 ++++++--- >>>>> src/security/security_manager.h | 6 +++-- >>>>> src/security/security_nop.c | 6 +++-- >>>>> src/security/security_selinux.c | 53 ++++++++++++++++++++++++++++++--------- >>>>> src/security/security_stack.c | 12 ++++++--- >>>>> tests/securityselinuxlabeltest.c | 2 +- >>>>> 11 files changed, 127 insertions(+), 46 deletions(-) >>>>> >>>> >>>> Why is it a (!chr_seclabel && chardevStdioLogd)? More to the point why >>>> is (!chr_seclabel) even matter? >>> >>> If you configure the label we shouldn't ignore it in some cases, that's >>> just wrong. If the label is set for the char device we will configure >>> it every time even if it will fail to start the guest, it's a >>> responsibility of the user to configure proper label if it is provided. >>> >> >> When email doesn't convey the question... Ugh... I'm also trying to >> speed learn an area of the code and review at the same time. >> >> If I go back to commit id 'f8b08d0e' where the original implementation >> to add labels for chardevs was done (but has been modified for patch 1 >> to change where the label is stored), I get the impression that a label >> should be added either from something specifically supplied for the >> <chardev> or to use the per domain one: >> >> "The source element may contain an optional seclabel to override the way >> that labelling is done on the socket path. If this element is not >> present, the security label is inherited from the per-domain setting." >> >> So if I look at the condition "(!chr_seclabel && chardevStdioLogd)" >> added by this patch to decide whether or not to supply the label, I'm >> left with the impression that if for this particular chardev a label >> doesn't exist *and* the configuration option chardevStdioLogd is true, >> then we're going to return happy status *and* not inherit the per-domain >> setting. >> >> So the bug is then that applying the default domain label for a chardev >> configured to use a stdio handle is incorrect? Perhaps I didn't get >> that from reading bz or the patch. > > Yes, that's the bug. If virtlogd is used to handle stdio for char > devices we shouldn't relabel the @path to the default labels, the > @path doesn't have to be accessible by the qemu process, it has to be > accessible by the virtlogd process. > >>>> IIUC, whether or not someone set the label for the chardev, for this >>>> particular issue/config where the chardev has a <log file=$path>, we >>>> don't want to set (or restore) the label. I feel like I'm missing >>>> something subtle. Maybe a bit more explanation of the adjustment would >>>> help me... >>> >>> This is not for the <log file=$path/> but for the <source path=$path/>. >>> We don't relabel $path for <log file=$path/> at all. >>> >> >> hmm.. ah, right... I kept scrolling back and forth in the bz and the >> docs, but missed this in the bz: >> >> 3) Check the virtlogd.log: >> error : virRotatingFileWriterEntryNew:113 : Unable to open file: >> /var/log/libvirt/qemu/log: Permission denied >> >> I guess I got lost in the power of suggestion of reading the docs >> regarding the "optional log file" that can be associated paragraph and >> trying to learn on the fly so that you at least get a review in a >> somewhat timely manner ;-) >> >>>> Wouldn't these changes end up selecting "any" chardev if >>>> chardevStdioLogd ended up being set regardless of whether they were >>>> actually using the log file? >>> >>> I don't know what you mean by this sentence? >>> >> >> Well let's see, chardevStdioLogd is set to true when meeting the two >> conditions a qemu.conf global "cfg->stdioLogd" && a per domain or >> emulator image capability "QEMU_CAPS_CHARDEV_FILE_APPEND". >> >> So, conceivably chardevStdioLogd could be true for *any* domain as long >> as those conditions are met, right? > > Yes, the two conditions are checked while starting a new domain in > qemuProcessPrepareDomain() and stored in the private date of that > domain. > >> If you have a domain that has chardev's which are not configured to use >> the stdio handler, then the chardevStdioLogd could still be true, right? > > No, if the @chardevStdioLogd is true all char devices for that domain > will use virtlogd. > This is the part I'm stuck on as to why - based on the previous assertion. I'm just not visualizing all those various chardev configs. Just so you know - I have to be out Friday, but will be back Monday. If you get someone else to ACK this one in the mean time - that's fine. John > The only issue I've just found out is that the code path for chardev > hot-plug isn't updated to use virtlogd when it should be so for > hot-plugged char devices we pass the path directly to QEMU. > > With this patch applied the hot-plug fails if virtlogd is used because > we don't relabel the path but we pass it directly to QEMU, this needs to > be fixed to not introduce a regression, sigh. > > Pavel > >> If that's the case and the chardev doesn't have a label associated, then >> we just return happy status and we do not inherit the per domain >> setting. Wouldn't that be incorrect? >> >> My concern is more we're making a change in a (mostly) common set of >> functions for a (very) specific problem. >> >> >>>> As an aside, I think there's an "oddity" when it comes to the Restore, >>>> but I'm not sure how to put it into words exactly. If a guest is running >>>> code prior to this set of changes, would it have successfully run a Set? >>>> If so, then after applying this change and restarting, the label >>>> wouldn't be reset, right? What happens at guest shutdown - does the >>>> label not get unset now? Of course this is all "interaction" with >>>> virtlogd restart that really throws a monkey wrench into things. >>> >>> No, that's not correct. The @chardevStdioLogd is stored in the status >>> XML (the one stored in /var/run/libvirt/qemu/$domain_name.xml). So when >>> the libvirtd is stopped and started with this patch applied the status >>> XML doesn't have the @chardevStdioLogd stored in it so it will be false >>> and we will reset the label. The @chardevStdioLogd is updated only when >>> the domain is started and we will store the value in the status XML >>> only with new libvirtd and only in that case we will not set/restore >>> the label. >>> >> >> hmmm.. Reading the bz indicates the 'virtlogd' daemon restarting... This >> is where all this gets a bit "odd" for me. Like I said it was a weird >> thing to even try and explain, but I think you talked me off the ledge >> of concern. >> >> John >> >>>> Also, why is the Smartcard chardev handling not using this >>> >>> The smartcard doesn't ever use virtlogd as stdio handler. >>> >>> Pavel >>> >> >> -- >> libvir-list mailing list >> libvir-list@xxxxxxxxxx >> https://www.redhat.com/mailman/listinfo/libvir-list -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
