Hi Stefan, I created a simple DMG file from MacOS to reproduce the problem: https://bugs.launchpad.net/qemu/+bug/1809304
Em qua, 2 de jan de 2019 às 08:47, Stefan Hajnoczi <stefa...@redhat.com> escreveu: > On Fri, Dec 21, 2018 at 09:58:03PM +0800, yuchenlin wrote: > > There is a possible hang in original binary searsh implemtation. That is > > if chunk1 = 4, chunk2 = 5, chunk3 = 4, and we go else case. > > > > The chunk1 will be still 4, and so on. > > > > Signed-off-by: yuchenlin <npes87...@gmail.com> > > --- > > block/dmg.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > Do you have an example dmg file that triggers this bug? > > > diff --git a/block/dmg.c b/block/dmg.c > > index 50e91aef6d..0e05702f5d 100644 > > --- a/block/dmg.c > > +++ b/block/dmg.c > > @@ -572,14 +572,14 @@ static inline uint32_t search_chunk(BDRVDMGState > *s, uint64_t sector_num) > > { > > /* binary search */ > > uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3; > > - while (chunk1 != chunk2) { > > + while (chunk1 <= chunk2) { > > chunk3 = (chunk1 + chunk2) / 2; > > if (s->sectors[chunk3] > sector_num) { > > - chunk2 = chunk3; > > + chunk2 = chunk3 - 1; > > What if chunk1 = 0 and chunk2 = 1? chunk3 = 0 and the new chunk2 value > would be 0xffffffff so the loop continues with out-of-bounds sectors[] > accesses! >