[Libvir] libvirt.c: avoid a double-free upon do_open failure

With a contrived example using more than 20 (the max permitted by the testing framework) domains, I got a double-free error: ==4821== Invalid free() / delete / delete[] ==4821== at 0x4A0560B: free (vg_replace_malloc.c:233) ==4821== by 0x4167F1: virReleaseConnect (hash.c:717) ==4821== by 0x4168E7: virUnrefConnect (hash.c:746) ==4821== by 0x40FCEB: do_open (libvirt.c:621) ==4821== by 0x40FDF1: virConnectOpenAuth (libvirt.c:682) ==4821== by 0x40D5B1: vshInit (virsh.c:4464) ==4821== by 0x40E67C: main (virsh.c:4985) ==4821== Address 0x4C3BA68 is 0 bytes inside a block of size 60 free'd ==4821== at 0x4A0560B: free (vg_replace_malloc.c:233) ==4821== by 0x40FCB3: do_open (libvirt.c:618) ==4821== by 0x40FDF1: virConnectOpenAuth (libvirt.c:682) ==4821== by 0x40D5B1: vshInit (virsh.c:4464) ==4821== by 0x40E67C: main (virsh.c:4985) error: failed to connect to the hypervisor ... here's one way to fix it: diff --git a/src/libvirt.c b/src/libvirt.c index defadc1..c19565f 100644 --- a/src/libvirt.c +++ b/src/libvirt.c @@ -615,7 +615,6 @@ do_open (const char *name, return ret; failed: - free (ret->name); if (ret->driver) ret->driver->close (ret); if (uri) xmlFreeURI(uri); virUnrefConnect(ret); At first, rather than removing the offending free, I inserted this line just after it: ret->name = NULL; which avoids leaking ->name even if some driver-specific close function fails to clean up properly. But IMHO if such a function doesn't clean up properly then *it* should be fixed, not all callers.