Re: [libvirt] [PATCH v2] qemu: Fix crash in virDomainMemoryStats with old qemu

If virDomainMemoryStats was run on a domain with virtio balloon driver running on an old qemu which supports QMP but does not support qom-list QMP command, libvirtd would crash. The reason is we did not check if qemuMonitorJSONGetObjectListPaths failed and moreover we even stored its result in an unsigned integer type. Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; --- Notes: version 2: - use signed type for i and j to avoid comparison between signed and unsigned types; gcc-- for not complaining about it src/qemu/qemu_monitor.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c index a968901..a2769db 100644 --- a/src/qemu/qemu_monitor.c +++ b/src/qemu/qemu_monitor.c @@ -1019,7 +1019,7 @@ qemuMonitorFindBalloonObjectPath(qemuMonitorPtr mon, virDomainObjPtr vm, const char *curpath) { - size_t i, j, npaths = 0, nprops = 0; + ssize_t i, j, npaths = 0, nprops = 0; int ret = 0; char *nextpath = NULL; qemuMonitorJSONListPathPtr *paths = NULL; @@ -1045,6 +1045,8 @@ qemuMonitorFindBalloonObjectPath(qemuMonitorPtr mon, VIR_DEBUG("Searching for Balloon Object Path starting at %s", curpath); npaths = qemuMonitorJSONGetObjectListPaths(mon, curpath, &paths); + if (npaths < 0) + return -1; for (i = 0; i < npaths && ret == 0; i++) { @@ -1061,6 +1063,11 @@ qemuMonitorFindBalloonObjectPath(qemuMonitorPtr mon, * then this version of qemu/kvm does not support the feature. */ nprops = qemuMonitorJSONGetObjectListPaths(mon, nextpath, &bprops); + if (nprops < 0) { + ret = -1; + goto cleanup; + } + for (j = 0; j < nprops; j++) { if (STREQ(bprops[j]->name, "guest-stats-polling-interval")) { VIR_DEBUG("Found Balloon Object Path %s", nextpath);