If the code jump to the cleanup before assagin value to xml pointer, libvirtd may get crashed when try to free an uninitialized pointer. backtrace: 0 0x00007ffff428d59c in free () from /lib64/libc.so.6 1 0x00007ffff721314a in virFree (ptrptr=ptrptr@entry=0x7fffc67f1b00) at util/viralloc.c:582 2 0x00007ffff7345ac4 in virDomainConfNWFilterInstantiate (vmname=<optimized out>, vmuuid=vmuuid@entry=0x7fffc0181ca8 "߉\237\\۔H\262\206z\340\302f\265\233z", net=<optimized out>, ignoreExists=ignoreExists@entry=true) at conf/domain_nwfilter.c:122 3 0x00007fffca5a77f6 in qemuProcessFiltersInstantiate (ignoreExists=true, def=0x7fffc0181ca0) at qemu/qemu_process.c:3028 4 qemuProcessReconnect (opaque=<optimized out>) at qemu/qemu_process.c:7653 5 0x00007ffff72c4895 in virThreadHelper (data=<optimized out>) at util/virthread.c:206 6 0x00007ffff45dcdd5 in start_thread () from /lib64/libpthread.so.0 7 0x00007ffff4305ead in clone () from /lib64/libc.so.6 Signed-off-by: Luyao Huang <lhuang(a)redhat.com&gt; --- src/conf/domain_nwfilter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/conf/domain_nwfilter.c b/src/conf/domain_nwfilter.c index 948b324..24b5f42 100644 --- a/src/conf/domain_nwfilter.c +++ b/src/conf/domain_nwfilter.c @@ -90,7 +90,7 @@ virDomainConfNWFilterInstantiate(const char *vmname, virConnectPtr conn = virGetConnectNWFilter(); virNWFilterBindingDefPtr def = NULL; virNWFilterBindingPtr binding = NULL; - char *xml; + char *xml = NULL; int ret = -1; VIR_DEBUG("vmname=%s portdev=%s filter=%s ignoreExists=%d",