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qemu: Prevent crash of libvirtd without guest agent configuration

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If users haven't configured guest agent then qemuAgentCommand() will
dereference a NULL 'mon' pointer, which causes crash of libvirtd when
using agent based cpu (un)plug.

With the patch, when the qemu-ga service isn't running in the guest,
a expected error "error: Guest agent is not responding: Guest agent
not available for now" will be raised, and the error "error: argument
unsupported: QEMU guest agent is not configured" is raised when the
guest hasn't configured guest agent.

GDB backtrace:

 (gdb) bt
 #0  virNetServerFatalSignal (sig=11, siginfo=<value optimized out>, context=<value optimized out>) at rpc/virnetserver.c:326
 #1  <signal handler called>
 #2  qemuAgentCommand (mon=0x0, cmd=0x7f39300017b0, reply=0x7f394b090910, seconds=-2) at qemu/qemu_agent.c:975
 #3  0x00007f39429507f6 in qemuAgentGetVCPUs (mon=0x0, info=0x7f394b0909b8) at qemu/qemu_agent.c:1475
 #4  0x00007f39429d9857 in qemuDomainGetVcpusFlags (dom=<value optimized out>, flags=9) at qemu/qemu_driver.c:4849
 #5  0x00007f3957dffd8d in virDomainGetVcpusFlags (domain=0x7f39300009c0, flags=8) at libvirt.c:9843

How to reproduce?

 # To start a guest without guest agent configuration
 # then run the following cmdline

 # virsh vcpucount foobar --guest
 error: End of file while reading data: Input/output error
 error: One or more references were leaked after disconnect from the hypervisor
 error: Failed to reconnect to the hypervisor

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=984821

Signed-off-by: Alex Jia <ajia@redhat.com>
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
This commit is contained in:
Alex Jia 2013-07-16 17:30:20 +08:00 committed by Peter Krempa
parent efab27afbf
commit 96518d4316
1 changed files with 26 additions and 0 deletions
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26
src/qemu/qemu_driver.c
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@ -4122,6 +4122,19 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
goto endjob;
}
if (priv->agentError) {
virReportError(VIR_ERR_AGENT_UNRESPONSIVE, "%s",
_("QEMU guest agent is not "
"available due to an error"));
goto endjob;
}
if (!priv->agent) {
virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
_("QEMU guest agent is not configured"));
goto endjob;
}
qemuDomainObjEnterAgent(vm);
ncpuinfo = qemuAgentGetVCPUs(priv->agent, &cpuinfo);
qemuDomainObjExitAgent(vm);
@ -4839,6 +4852,19 @@ qemuDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_QUERY) < 0)
goto cleanup;
if (priv->agentError) {
virReportError(VIR_ERR_AGENT_UNRESPONSIVE, "%s",
_("QEMU guest agent is not "
"available due to an error"));
goto endjob;
}
if (!priv->agent) {
virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
_("QEMU guest agent is not configured"));
goto endjob;
}
if (!virDomainObjIsActive(vm)) {
virReportError(VIR_ERR_OPERATION_INVALID, "%s",
_("domain is not running"));