Re: [libvirt] [PATCH 1/3] conf: Properly truncate wide character names in virDomainObjGetShortName

On 08/23/2017 07:47 AM, Martin Kletzander wrote: > We always truncated the name at 20 bytes instead of characters. In > case 20 bytes were in the middle of a multi-byte character, then the > string became invalid and various parts of the code would error > out (e.g. XML parsing of that string). Let's instead properly > truncate it after 20 characters instead. > > In some cases the truncation didn't even work (as can be seen from the > modified tests), which is fixed by this as well. Didn't work as well? Try at all... As a test I changed the name of pcie-expander-bus to 80 characters and all 80 were printed. I think this goes against your original intention of a shortname... > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1448766 > > Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com&gt; > --- > src/conf/domain_conf.c | 30 +++++++++++++++++++--- > .../qemuxml2argv-aarch64-virt-default-nic.args | 2 +- > .../qemuxml2argv-hugepages-pages2.args | 4 +-- > .../qemuxml2argv-hugepages-pages3.args | 5 ++-- > .../qemuxml2argv-hugepages-pages5.args | 4 +-- > .../qemuxml2argv-hugepages-pages6.args | 2 +- > .../qemuxml2argv-pcie-expander-bus.args | 2 +- > 7 files changed, 37 insertions(+), 12 deletions(-) > Can we add a multibyte name test? These just modify existing tests (I think wrongly too).

> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c > index 47eba4dbb315..9a46ceece2d6 100644 > --- a/src/conf/domain_conf.c > +++ b/src/conf/domain_conf.c > @@ -27131,6 +27131,8 @@ virDomainDefHasMemballoon(const virDomainDef *def) > } > > > +#define VIR_DOMAIN_SHORT_NAME_MAX 20 > + > /** > * virDomainObjGetShortName: > * @vm: Machine for which to get a name > @@ -27141,15 +27143,37 @@ virDomainDefHasMemballoon(const virDomainDef *def) > char * > virDomainObjGetShortName(const virDomainDef *def) > { > - const int dommaxlen = 20; > + wchar_t wshortname[VIR_DOMAIN_SHORT_NAME_MAX + 1] = {0}; > + size_t len = 0; > + char *shortname = NULL; > char *ret = NULL; > It would seem that we could figure there were multibyte chars in the name "if strlen(def->name) != mbstowcs(NULL, def->name, 0)" and not do any conversion, leaving the old code "as is" (mostly) and then implementing something for these wide characters.

Of course I'm not getting anything other than -1 returned for the mbstowcs and I didn't really want to dig any further, so I leave it up to you!

I tried to modify the same test and change the name to "ÄèÎØÛ", but the mbstowcs kept returning -1, until I added: if (setlocale(LC_ALL, "en_US.UTF-8") == NULL) {

But how does one know which locale to use? From my quick read of the mbstowcs man page it seems a locale needs to be set first. I also tried the man page example of "Grüße!" and that worked with UTF-8.

> - ignore_value(virAsprintf(&ret, "%d-%.*s", > - def->id, dommaxlen, def->name)); > + if (mbstowcs(wshortname, def->name, VIR_DOMAIN_SHORT_NAME_MAX) == (size_t) -1) { > + virReportError(VIR_ERR_INVALID_ARG, "%s", > + _("Cannot convert domain name to wide character string")); > + return NULL; > + } > + > + len = wcstombs(NULL, wshortname, 0); > + if (len == (size_t) -1) > + return NULL; > > + if (VIR_ALLOC_N(shortname, len + 1) < 0) > + return NULL; > + > + if (wcstombs(shortname, wshortname, len) == (size_t) -1) { > + virReportError(VIR_ERR_INVALID_ARG, "%s", > + _("Cannot convert domain name from wide character string")); > + goto cleanup; > + } > + > + ignore_value(virAsprintf(&ret, "%d-%s", def->id, def->name)); You go through all this trouble and still write def->name! I didn't realize that at first either - kept wondering why the whole damn name was being printed!