path: root/pack-objects.h
diff options
authorJeff King <>2018-11-20 09:46:38 (GMT)
committerJunio C Hamano <>2018-11-21 04:50:16 (GMT)
commitbc35ac1a6a844fc3484833afee41260e1d47042e (patch)
tree674f023deee0b15b16cb004e8db54ad3d7f6658d /pack-objects.h
parentfe0ac2fb7f8e87d37ef83dcee2d93901d58d8277 (diff)
pack-objects: fix tree_depth and layer invariants
Commit 108f530385 (pack-objects: move tree_depth into 'struct packing_data', 2018-08-16) dynamically manages a tree_depth array in packing_data that maintains one of these invariants: 1. tree_depth is NULL (i.e., the requested options don't require us to track tree depths) 2. tree_depth is non-NULL and has as many entries as the "objects" array We maintain (2) by: a. When the objects array grows, grow tree_depth to the same size (unless it's NULL, in which case we can leave it). b. When a caller asks to set a depth via oe_set_tree_depth(), if tree_depth is NULL we allocate it. But in (b), we use the number of stored objects, _not_ the allocated size of the objects array. So we can run into a situation like this: 1. packlist_alloc() needs to store the Nth object, so it grows the objects array to M, where M > N. 2. oe_set_tree_depth() wants to store a depth, so it allocates an array of length N. Now we've violated our invariant. 3. packlist_alloc() needs to store the N+1th object. But it _doesn't_ grow the objects array, since N <= M still holds. We try to assign to tree_depth[N+1], which is out of bounds. That doesn't happen in our test scripts, because the repositories they use are so small, but it's easy to trigger by running: echo HEAD | git pack-objects --revs --delta-islands --stdout >/dev/null in any reasonably-sized repo (like git.git). We can fix it by always growing the array to match pack->nr_alloc, not pack->nr_objects. Likewise for the "layer" array from fe0ac2fb7f (pack-objects: move 'layer' into 'struct packing_data', 2018-08-16), which has the same bug. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'pack-objects.h')
1 files changed, 2 insertions, 2 deletions
diff --git a/pack-objects.h b/pack-objects.h
index ad3c208..741e6f8 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -364,7 +364,7 @@ static inline void oe_set_tree_depth(struct packing_data *pack,
unsigned int tree_depth)
if (!pack->tree_depth)
- ALLOC_ARRAY(pack->tree_depth, pack->nr_objects);
+ ALLOC_ARRAY(pack->tree_depth, pack->nr_alloc);
pack->tree_depth[e - pack->objects] = tree_depth;
@@ -381,7 +381,7 @@ static inline void oe_set_layer(struct packing_data *pack,
unsigned char layer)
if (!pack->layer)
- ALLOC_ARRAY(pack->layer, pack->nr_objects);
+ ALLOC_ARRAY(pack->layer, pack->nr_alloc);
pack->layer[e - pack->objects] = layer;