[15/20] commit-graph.c: prevent overflow in `fill_commit_in_graph()`

Commit Message

Taylor Blau July 12, 2023, 11:38 p.m. UTC

In a similar spirit as previous commits, ensure that we don't overflow
when the lex_index of the commit we are trying to fill out exceeds
2^32-1/(g->hash_len+16).

The other hunk touched in this patch is not susceptible to overflow,
since an explicit cast is made to a 64-bit unsigned value. For clarity
and consistency with the rest of the commits in this series, avoid a
tricky to reason about cast, and use `st_mult()` directly.

Signed-off-by: Taylor Blau <[e-mail]>
---
 commit-graph.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

diff --git a/commit-graph.c b/commit-graph.c
index ceaeb8b785..ca1d997516 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -837,7 +837,7 @@  static int fill_commit_in_graph(struct repository *r,
 	fill_commit_graph_info(item, g, pos);
 
 	lex_index = pos - g->num_commits_in_base;
-	commit_data = g->chunk_commit_data + (g->hash_len + 16) * lex_index;
+	commit_data = g->chunk_commit_data + st_mult(g->hash_len + 16, lex_index);
 
 	item->object.parsed = 1;
 
@@ -859,7 +859,7 @@  static int fill_commit_in_graph(struct repository *r,
 	}
 
 	parent_data_ptr = (uint32_t*)(g->chunk_extra_edges +
-			  4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
+			  st_mult(4, edge_value & GRAPH_EDGE_LAST_MASK));
 	do {
 		edge_value = get_be32(parent_data_ptr);
 		pptr = insert_parent_or_die(r, g,