From bc35ac1a6a844fc3484833afee41260e1d47042e Mon Sep 17 00:00:00 2001 From: Jeff King Date: Tue, 20 Nov 2018 04:46:38 -0500 Subject: [PATCH] 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 --- pack-objects.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/pack-objects.h b/pack-objects.h index ad3c208764..741e6f862d 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; }