Re: [libvirt] [PATCH 2/5] conf: fix detection of infinite backing loop

While trying to refactor the backing file chain, I noticed that if you have a self-referential qcow2 file via a relative name: qemu-img create -f qcow2 loop 10M qemu-img rebase -u -f qcow2 -F qcow2 -b loop loop then libvirt was creating a chain 2 deep before realizing it had hit a loop; furthermore, virStorageFileChainCheckBroken was not identifying the chain as broken. With this patch, the loop is detected when the chain is only 1 deep; still enough for storage volume XML to display the file, but now with a proper error report about where the loop was found. * src/util/virstoragefile.c (virStorageFileGetMetadataRecurse): Mark chain broken if OOM or infinite loop occurs. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- src/util/virstoragefile.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c index 017717c..39e4c19 100644 --- a/src/util/virstoragefile.c +++ b/src/util/virstoragefile.c @@ -1074,15 +1074,21 @@ virStorageFileGetMetadataRecurse(const char *path, const char *directory,

path, format, (int)uid, (int)gid, allow_probe); virStorageFileMetadataPtr ret = NULL; + char *canonical = canonicalize_file_name(path);

- if (virHashLookup(cycle, path)) { + /* Hash by canonical name */ + if (!canonical) { + virReportOOMError(); + goto cleanup; + } + if (virHashLookup(cycle, canonical)) { virReportError(VIR_ERR_INTERNAL_ERROR, _("backing store for %s is self-referential"), path); - return NULL; + goto cleanup; } - if (virHashAddEntry(cycle, path, (void *)1) < 0) - return NULL; + if (virHashAddEntry(cycle, canonical, (void *)1) < 0) + goto cleanup; if ((fd = virFileOpenAs(path, O_RDONLY, 0, uid, gid, 0)) < 0) { virReportSystemError(-fd, _("Failed to open file '%s'"), path);