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!
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