avoid possible overflow in delta size filtering computation

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> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Nicolas Pitre committed Mar 24, 2009 at 15:56 UTC 720fe22d50a58e3308124ec7f5b0fa6c17be3d22

1 file changed +1 -1

builtin-pack-objects.c

+1 -1

@@ -1265,7 +1265,7 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,

1265 max_size = trg_entry->delta_size;

1266 ref_depth = trg->depth;

1267 }

1268 - max_size = max_size * (max_depth - src->depth) /

1268 + max_size = (uint64_t)max_size * (max_depth - src->depth) /

1269 (max_depth - ref_depth + 1);

1270 if (max_size == 0)

1271 return 0;