Re: [Libguestfs] [PATCH v2 1/2] lib: change how hbin sections are read.

On Tue, Feb 14, 2017 at 12:05:20PM -0500, Dawid Zamirski wrote: > * hivex_open: when looping over hbin sections (aka pages), handle a >   case where following hbin section may not begin at exactly at the > end >   of previous one. If this happens, scan the page section until > next >   one is found and validate it by checking declared offset with > actual >   one - if they match, all is good and we can safely move on. > > Rationale: there are registry hives there is some garbage data > between > hbin section but the hive is still perfectly usable as long as the > offsets stated in hbin headers are correct. > --- >  lib/handle.c | 39 ++++++++++++++++++++++++++++++++++----- >  1 file changed, 34 insertions(+), 5 deletions(-) > > diff --git a/lib/handle.c b/lib/handle.c > index 4565d7d..e183ff2 100644 > --- a/lib/handle.c > +++ b/lib/handle.c > @@ -226,11 +226,30 @@ hivex_open (const char *filename, int flags) >          page->magic[1] != 'b' || >          page->magic[2] != 'i' || >          page->magic[3] != 'n') { > -      SET_ERRNO (ENOTSUP, > -                 "%s: trailing garbage at end of file " > -                 "(at 0x%zx, after %zu pages)", > -                 filename, off, pages); > -      goto error; > + > +      DEBUG (2, > +             "page not found at expected offset 0x%zx, " > +             "seeking until one is found or EOF is reached", > +             off); > + > +      int found = 0; > +      while (off < h->endpages) { GCC 7 warns: handle.c: In function 'hivex_open': handle.c:236:13: error: missed loop optimization, the loop counter may overflow [-Werror=unsafe-loop-optimizations]        while (off < h->endpages) {              ^ I suspect this means that GCC might try to turn this into an infinite loop. There are actually a few more of these in the existing code - I'm going to push a patch to fix these in a minute. Rich.