daemon: avoid memleak when ListAll returns nothing
authorEric Blake <eblake@redhat.com>
Fri, 13 Mar 2015 23:01:43 +0000 (17:01 -0600)
committerEric Blake <eblake@redhat.com>
Mon, 16 Mar 2015 16:21:06 +0000 (10:21 -0600)
commit117f60ca53eb36aa7751573ac274850bd96a4799
treed00aee87e67a023aa32f01eea65754f3c6d5f26d
parenta4613757145ad7d4b87fb5a13f250ca77a4ab57f
daemon: avoid memleak when ListAll returns nothing

Commit 4f25146 (v1.2.8) managed to silence Coverity, but at the
cost of a memory leak detected by valgrind:
==24129== 40 bytes in 5 blocks are definitely lost in loss record 355 of 637
==24129==    at 0x4A08B1C: realloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==24129==    by 0x5084B8E: virReallocN (viralloc.c:245)
==24129==    by 0x514D5AA: virDomainObjListExport (domain_conf.c:22200)
==24129==    by 0x201227DB: qemuConnectListAllDomains (qemu_driver.c:18042)
==24129==    by 0x51CC1B6: virConnectListAllDomains (libvirt-domain.c:6797)
==24129==    by 0x14173D: remoteDispatchConnectListAllDomains (remote.c:1580)
==24129==    by 0x121BE1: remoteDispatchConnectListAllDomainsHelper (remote_dispatch.h:1072)

In short, every time a client calls a ListAll variant and asks
for the resulting list, but there are 0 elements to return, we
end up leaking the 1-entry array that holds the NULL terminator.

What's worse, a read-only client can access these functions in a
tight loop to cause libvirtd to eventually run out of memory; and
this can be considered a denial of service attack against more
privileged clients.  Thankfully, the leak is so small (8 bytes per
call) that you would already have some other denial of service with
any guest calling the API that frequently, so an out-of-memory
crash is unlikely enough that this did not warrant a CVE.

* daemon/remote.c (remoteDispatchConnectListAllDomains)
(remoteDispatchDomainListAllSnapshots)
(remoteDispatchDomainSnapshotListAllChildren)
(remoteDispatchConnectListAllStoragePools)
(remoteDispatchStoragePoolListAllVolumes)
(remoteDispatchConnectListAllNetworks)
(remoteDispatchConnectListAllInterfaces)
(remoteDispatchConnectListAllNodeDevices)
(remoteDispatchConnectListAllNWFilters)
(remoteDispatchConnectListAllSecrets)
(remoteDispatchNetworkGetDHCPLeases): Plug leak.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 3c2ff5029b83c9b33be0f1607a3c61f4f5850612)
daemon/remote.c