set useBinarySpecificLabel = true when calling qemuSecurityCommandRun
for the passt process, so that the new process context will include
the binary-specific label that should be used for passt (passt_t)
rather than svirt_t (as would happen if useBinarySpecificLabel was
false). (The MCS part of the label, which is common to all child
processes related to a particular qemu domain instance, is also set).
Resolves: https://bugzilla.redhat.com/2172267
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Normally when a child process is started by libvirt, the SELinux label
of that process is set to virtd_t (plus an MCS range). In at least one
case (passt) we need for the SELinux label of a child process label to
match the label that the binary would have transitioned to
automatically if it had been run standalone (in the case of passt,
that label is passt_t).
This patch modifies virSecuritySELinuxSetChildProcessLabel() (and all
the functions above it in the call chain) so that the toplevel
function can set a new argument "useBinarySpecificLabel" to true. If
it is true, then virSecuritySELinuxSetChildProcessLabel() will call
the new function virSecuritySELinuxContextSetFromFile(), which uses
the selinux library function security_compute_create() to determine
what would be the label of the new process if it had been run
standalone (rather than being run by libvirt) - the MCS range from the
normally-used label is added to this newly derived label, and that is
what is used for the new process rather than whatever is in the
domain's security label (which will usually be virtd_t).
In order to easily verify that nothing was broken by these changes to
the call chain, all callers currently set useBinarySpecificPath =
false, so all behavior should be completely unchanged. (The next
patch will set it to true only for the case of running passt.)
https://bugzilla.redhat.com/2172267
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
When starting (some) external helpers, callers of
qemuSecurityCommandRun() pass &exitstatus variable, to learn the
exit code of helper process (with qemuTPMEmulatorStart() being
the only exception). Then, if the status wasn't zero they produce
a generic error message, like:
"Starting of helper process failed. exitstatus=%d"
or, in case of qemuPasstStart():
"Could not start 'passt': %s"
This is needless as virCommandRun() (that's called under the
hood), can do both for us, if NULL was passed instead of
@exitstatus. Not only it appends exit status, it also reads
stderr of failed command producing comprehensive error message:
Child process (${args}) unexpected exit status ${exitstatus}: ${stderr}
Therefore, pass NULL everywhere. But in contrast with one of
previous commits which removed @cmdret argument, there could be a
sensible caller which might want to process exit code. So keep
the argument for now and just pass NULL.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Every single caller of qemuSecurityCommandRun() calls the
function as:
if (qemuSecurityCommandRun(..., &cmdret) < 0)
goto cleanup;
if (cmdret < 0)
goto cleanup;
(modulo @exitstatus shenanigans)
Well, there's no need for such complication. There isn't a single
caller (and probably will never be (TM)), that would need to
distinguish the reason for the failure. Therefore,
qemuSecurityCommandRun() can be made to pass the retval of
virCommandRun() called under the hood.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
The usual pattern when starting a helper daemon is:
if (qemuSecurityCommandRun(..., &exitstatus, &cmdret) < 0)
goto cleanup;
if (cmdret < 0 || exitstatus != 0) {
virReportError();
goto cleanup;
}
The only problem with this pattern is that if virCommandRun()
fails (i.e. cmdret < 0), then proper error was already reported.
But in this pattern we overwrite it (usually with less specific)
error.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
QEMU's "reconnect" option of "-netdev stream" tells QEMU to
periodically (period is given in seconds as an argument to the option)
attempt to reconnect to the same passt socket to which it had
originally connected to. This is useful in cases where the passt
process terminates, and libvirtd starts a new passt process in its
place (which doesn't happen yet, but will happen automatically after
an upcoming patch in this series).
Since there is no real hueristic for determining the "best" value of
the reconnect interval, rather than clutter up config with a knob that
nobody knows how to properly twiddle, we just set the reconnect timer
to 5 seconds.
"-netdev stream" first appeared in QEMU 7.2.0, but the reconnect
option won't be available until QEMU 8.0.0, so we need to check QEMU
capabilities just in case someone is using QEMU 7.2.0 (and thus can
support passt backend, but not reconnect)
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Just like it can't remove its own PID files, passt can't unlink its
own socket upon exit (unless the initialisation fails), because it
has no access to the filesystem at runtime.
Remove the socket file in qemuPasstKill().
Fixes: a56f0168d576 ("qemu: hook up passt config to qemu domains")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
The way we start passt currently is: we use
virCommandSetPidFile() to use our virCommand machinery to acquire
the PID file and leak opened FD into passt. Then, we use
virPidFile*() APIs to read the PID file (which is needed when
placing it into CGroups or killing it). But this does not fly
really because passt daemonizes itself. Thus the process we
started dies soon and thus the PID file is closed and unlocked.
We could work around this by passing '--foreground' argument, but
that weakens passt as it can't create new PID namespace (because
it doesn't fork()).
The solution is to let passt write the PID file, but since it
does not lock the file and closes it as soon as it is written, we
have to switch to those virPidFile APIs which don't expect PID
file to be locked.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
There are two places where we kill passt:
1) qemuPasstStop() - called transitively from qemuProcessStop(),
2) qemuPasstStart() - after failed start.
Now, the code from 2) lack error preservation (so if there's
another error during cleanup we might overwrite the original
error). Therefore, move the internals of qemuPasstStop() into a
separate function and call it from both places.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
When starting passt, it may write something onto its stderr
(convincing it to print even more is addressed later). Pass this
string we read to user.
Since we're not daemonizing passt anymore (see previous commit),
we can let virCommand module do all the heavy lifting and switch
to virCommandSetErrorBuffer() instead of reading error from an
FD.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
When passt is started, it daemonizes itself by default. There's
no point in having our virCommand module daemonize it too.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
If qemuPasstGetPid() fails, or the passt's PID is -1 then
qemuPasstSetupCgroup() returns early without any error message
set. Report an appropriate error.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
This reverts commit 0c4e716835eaf2a575bd063fde074c0fc7c4e4d4.
This patch was pushed by my mistake. Even though it got ACKed on
the list, I've raised couple of issues with it. They will be
fixed in next commits.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
I initially had the passt process being started in an identical
fashion to the slirp-helper - libvirt was daemonizing the new process
and recording its pid in a pidfile. The problem with this is that,
since it is daemonized immediately, any startup error in passt happens
after the daemonization, and thus isn't seen by libvirt - libvirt
believes that the process has started successfully and continues on
its merry way. The result was that sometimes a guest would be started,
but there would be no passt process for qemu to use for network
traffic.
Instead, we should be starting passt in the same manner we start
dnsmasq - we just exec it as normal (along with a request that passt
create the pidfile, which is just another option on the passt
commandline) and wait for the child process to exit; passt then has a
chance to parse its commandline and complete all the setup prior to
daemonizing itself; if it encounters an error and exits with a non-0
code, libvirt will see the code and know about the failure. We can
then grab the output from stderr, log that so the "user" has some idea
of what went wrong, and then fail the guest startup.
Signed-off-by: Laine Stump <laine@redhat.com>
This commented-out option was pointed out by jtomko during review, but
I missed taking it out when addressing his comments.
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
This attribute was added to support setting the --interface option for
passt, but in a post-push/pre-9.0-release review, danpb pointed out
that it would be better to use the existing <source dev='xxx'/>
attribute to set --interface rather than creating a new attribute (in
the wrong place). So we remove backend/upstream, and change the passt
commandline creation to grab the name for --interface from source/dev.
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Jumping to the error label and reading the pidfile does not make sense
until we reached qemuSecurityCommandRun which creates the pidfile.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
The pidfile is guaranteed to be non-NULL (thanks to glib allocation
functions) and it's dereferenced two lines above anyway.
Reported by coverity:
/src/qemu/qemu_passt.c: 278 in qemuPasstStart()
272 return 0;
273
274 error:
275 ignore_value(virPidFileReadPathIfLocked(pidfile, &pid));
276 if (pid != -1)
277 virProcessKillPainfully(pid, true);
>>> CID 404360: Null pointer dereferences (REVERSE_INULL)
>>> Null-checking "pidfile" suggests that it may be null, but it
>>> has already been dereferenced on all paths leading to the check.
278 if (pidfile)
279 unlink(pidfile);
280
281 return -1;
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
This consists of (1) adding the necessary args to the qemu commandline
netdev option, and (2) starting a passt process prior to starting
qemu, and making sure that it is terminated when it's no longer
needed. Under normal circumstances, passt will terminate itself as
soon as qemu closes its socket, but in case of some error where qemu
is never started, or fails to startup completely, we need to terminate
passt manually.
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
