[PATCH] avoid possible overflow in delta size filtering computation
- From
Nicolas Pitre <nico@cam.org>
- Date
- Mar 24, 2009, 19:56 UTC
- Message-ID
- <alpine.LFD.2.00.0903241535010.26337@xanadu.home>
On a 32-bit system, the maximum possible size for an object is less than 4GB, while 64-bit systems may cope with larger objects. Due to this limitation, variables holding object sizes are using an unsigned long type (32 bits on 32-bit systems, or 64 bits on 64-bit systems).
When large objects are encountered, and/or people play with large delta depth values, it is possible for the maximum allowed delta size computation to overflow, especially on a 32-bit system. When this occurs, surviving result bits may represent a value much smaller than what it is supposed to be, or even zero. This prevents some objects from being deltified although they do get deltified when a smaller depth limit is used. Fix this by always performing a 64-bit multiplication.
Signed-off-by: Nicolas Pitre <nico@cam.org>
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c index 3a4bdbb..9fc3b35 100644 --- a/builtin-pack-objects.c +++ b/builtin-pack-objects.c @@ -1293,7 +1293,7 @@ static int try_delta(struct unpacked *trg, struct unpacked *src, max_size = trg_entry->delta_size; ref_depth = trg->depth; } - max_size = max_size * (max_depth - src->depth) / + max_size = (uint64_t)max_size * (max_depth - src->depth) / (max_depth - ref_depth + 1); if (max_size == 0) return 0;