From: Jeff King <peff@peff.net>
To: git@vger.kernel.org
Cc: Christian Couder <chriscool@tuxfamily.org>,
Derrick Stolee <dstolee@microsoft.com>
Subject: [PATCH 1/3] pack-objects: fix tree_depth and layer invariants
Date: Tue, 20 Nov 2018 04:46:38 -0500 [thread overview]
Message-ID: <20181120094638.GA22742@sigill.intra.peff.net> (raw)
In-Reply-To: <20181120094451.GA21725@sigill.intra.peff.net>
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 <peff@peff.net>
---
pack-objects.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/pack-objects.h b/pack-objects.h
index feb6a6a05e..f31ac1c81c 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -412,7 +412,7 @@ 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;
}
@@ -429,7 +429,7 @@ 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;
}
--
2.20.0.rc0.715.gf6b01ab3e1
next prev parent reply other threads:[~2018-11-20 9:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-20 9:44 [PATCH 0/3] delta-island fixes Jeff King
2018-11-20 9:46 ` Jeff King [this message]
2018-11-20 16:37 ` [PATCH 1/3] pack-objects: fix tree_depth and layer invariants Duy Nguyen
2018-11-22 16:50 ` Jeff King
2018-11-21 4:52 ` Junio C Hamano
2018-11-20 9:48 ` [PATCH 2/3] pack-objects: zero-initialize tree_depth/layer arrays Jeff King
2018-11-20 9:50 ` [PATCH 3/3] pack-objects: fix off-by-one in delta-island tree-depth computation Jeff King
2018-11-20 15:06 ` [PATCH 0/3] delta-island fixes Derrick Stolee
2018-11-22 16:43 ` Jeff King
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