Re: [libvirt] [PATCH 3/3] util: storage: Improve error message when requesting image above 'start'

On Wed, Apr 22, 2015 at 14:09:18 +0200, Martin Kletzander wrote: > On Tue, Apr 21, 2015 at 05:52:14PM +0200, Peter Krempa wrote: > >When a user would specify a backing chain index that is above the start > >point libvirt would report a rather unhelpful error: > > > >invalid argument: could not find backing store 1 in chain for 'sub/link2' > > > >This patch adds an explicit check that the index is below start point in > >the backing store and reports the following error if not: > > > >invalid argument: requested backing store index 1 is above 'sub/../qcow2' in chain for 'sub/link2' > > > >Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1177062 > >--- > > src/util/virstoragefile.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > >diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c > >index c9d3977..2a2f238 100644 > >--- a/src/util/virstoragefile.c > >+++ b/src/util/virstoragefile.c > >@@ -1341,6 +1341,15 @@ virStorageFileChainLookup(virStorageSourcePtr chain, > > *parent = startFrom; > > } > > > >+ if (idx && idx < i) { > >+ virReportError(VIR_ERR_INVALID_ARG, > >+ _("requested backing store index %u is above '%s' " > >+ "in chain for '%s'"), > >+ idx, NULLSTR(startFrom->path), NULLSTR(start)); > > Possible crasher: startFrom can be NULL here, rather move the check > into the previous block where the parent is being set when found (idx > can't be < i when there is no startFrom anyway). You can then avoid > cleaning up the *parent here -+ > | > +-----------+ > | > v Actually right at the beginning of the function @parent gets filled by a pointer to a local virStorageSource pointer (stack allocated) in case the caller passed NULL as @parent. This allows to use the variable since it is used in the lookup loop even if the user doesn't pass it.

Don't worry, I had the same thought when I wrote the condition :)