util: storage: Fix crash of libvirtd on network backed guest block-pull

For guests backed by gluster volumes (or other network storage) we don't
fill the backing chain (see qemuDomainDetermineDiskChain). This leaves
the "relPath" field of the top image NULL. This causes a crash in
virStorageFileChainLookup() when looking up a backing element for such a
disk.

Since I'm working on adding support for network storage and one of the
steps will make the "relPath" field optional let's use STREQ_NULLABLE
instead of STREQ in virStorageFileChainLookup() to avoid the problem.

diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 2feda67699e9d5437b950c0689d9d5b4826a7fe0..c9b6187fc724e5e5222d0750a0033ea6187def64 100644 (file)
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -1591,7 +1591,7 @@ virStorageFileChainLookup(virStorageSourcePtr chain,
             if (idx == i)
                 break;
         } else {
-            if (STREQ(name, chain->relPath))
+            if (STREQ_NULLABLE(name, chain->relPath))
                 break;
             if (nameIsFile && (chain->type == VIR_STORAGE_TYPE_FILE ||
                                chain->type == VIR_STORAGE_TYPE_BLOCK)) {