From ee6a7924124b2a9030da55c94a27829e410b3b64 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Mon, 9 Oct 2023 17:05:47 -0400 Subject: commit-graph: bounds-check generation overflow chunk If the generation entry in a commit-graph doesn't fit, we instead insert an offset into a generation overflow chunk. But since we don't record the size of the chunk, we may read outside the chunk if the offset we find on disk is malicious or corrupted. We can't check the size of the chunk up-front; it will vary based on how many entries need overflow. So instead, we'll do a bounds-check before accessing the chunk memory. Unfortunately there is no error-return from this function, so we'll just have to die(), which is what it does for other forms of corruption. As with other cases, we can drop the st_mult() call, since we know our bounds-checked value will fit within a size_t. Before this patch, the test here actually "works" because we read garbage data from the next chunk. And since that garbage data happens not to provide a generation number which changes the output, it appears to work. We could construct a case that actually segfaults or produces wrong output, but it would be a bit tricky. For our purposes its sufficient to check that we've detected the bounds error. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- commit-graph.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'commit-graph.c') diff --git a/commit-graph.c b/commit-graph.c index ca26870d1b..f446e76c28 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -451,8 +451,9 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s, if (s->commit_graph_generation_version >= 2) { read_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA, graph_read_generation_data, graph); - pair_chunk_unsafe(cf, GRAPH_CHUNKID_GENERATION_DATA_OVERFLOW, - &graph->chunk_generation_data_overflow); + pair_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA_OVERFLOW, + &graph->chunk_generation_data_overflow, + &graph->chunk_generation_data_overflow_size); if (graph->chunk_generation_data) graph->read_generation_data = 1; @@ -896,7 +897,10 @@ static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, die(_("commit-graph requires overflow generation data but has none")); offset_pos = offset ^ CORRECTED_COMMIT_DATE_OFFSET_OVERFLOW; - graph_data->generation = item->date + get_be64(g->chunk_generation_data_overflow + st_mult(8, offset_pos)); + if (g->chunk_generation_data_overflow_size / sizeof(uint64_t) <= offset_pos) + die(_("commit-graph overflow generation data is too small")); + graph_data->generation = item->date + + get_be64(g->chunk_generation_data_overflow + sizeof(uint64_t) * offset_pos); } else graph_data->generation = item->date + offset; } else -- cgit v1.2.3