From 209250ef38f353f174ee9e90e55f5a4605449f70 Mon Sep 17 00:00:00 2001 From: Taylor Blau Date: Wed, 12 Jul 2023 19:37:57 -0400 Subject: [PATCH] commit-graph.c: prevent overflow in add_graph_to_chain() The commit-graph uses a fanout table with 4-byte entries to store the number of commits at each shard of the commit-graph. So it is OK to have a commit graph with as many as 2^32-1 stored commits. But we risk overflowing any computation which may exceed the 32-bit (unsigned) maximum when those computations are (incorrectly) performed using 32-bit operands. There are a couple of spots in `add_graph_to_chain()` where we could potentially overflow the result: - First, when comparing the list of existing entries in the commit-graph chain. It is unlikely that this should ever overflow, since it would require having roughly 2^32-1/g->hash_len commit-graphs in the chain. But let's guard that computation with a `st_mult()` just to be safe. - Second, when computing the number of commits in the graph added to the front of the chain. This value is also a 32-bit unsigned, but we should make sure that it does not grow beyond the maximum value. Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano --- commit-graph.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/commit-graph.c b/commit-graph.c index 86c76bd2f8..17ab3e8029 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -482,7 +482,7 @@ static int add_graph_to_chain(struct commit_graph *g, if (!cur_g || !oideq(&oids[n], &cur_g->oid) || - !hasheq(oids[n].hash, g->chunk_base_graphs + g->hash_len * n)) { + !hasheq(oids[n].hash, g->chunk_base_graphs + st_mult(g->hash_len, n))) { warning(_("commit-graph chain does not match")); return 0; } @@ -492,8 +492,15 @@ static int add_graph_to_chain(struct commit_graph *g, g->base_graph = chain; - if (chain) + if (chain) { + if (unsigned_add_overflows(chain->num_commits, + chain->num_commits_in_base)) { + warning(_("commit count in base graph too high: %"PRIuMAX), + (uintmax_t)chain->num_commits_in_base); + return 0; + } g->num_commits_in_base = chain->num_commits + chain->num_commits_in_base; + } return 1; }