Thread (8 messages) flat view 8 messages, 5 authors, 2023-08-11

Re: leak in jt/path-filter-fix, was Re: What's cooking in git.git (Aug 2023, #01; Wed, 2)

From: Jeff King <hidden>
Date: 2023-08-08 20:20:22
Subsystem: the rest · Maintainer: Linus Torvalds 

On Tue, Aug 08, 2023 at 03:22:41PM -0400, Jeff King wrote:

Subject: [PATCH] commit-graph: fix small leak with invalid changedPathsVersion

When writing a commit graph, we sanity-check the value of
commitgraph.changedPathsVersion and return early if it's invalid. But we
only do so after allocating the write_commit_graph_context, meaing we
leak it. We could "goto cleanup" to fix this, but instead let's push
this check to the top of the function with the other early checks which
return before doing any work.
I am tempted to do this on top, but maybe it is just churn. I dunno.

-- >8 --
Subject: [PATCH] commit-graph: store write context on stack rather than heap

In write_commit_graph(), we allocate our context struct on the heap.
But there's no reason to do so, since it's small and we always free it
when exiting the function. Converting it to a stack variable is slightly
more efficient, but also can prevent some leaks (such as the one fixed
in the previous commit, though to be fair this only helps for such a
limited leak; once any sub-fields of the struct require allocation, it
has to be cleaned up).

Signed-off-by: Jeff King <redacted>
---
 commit-graph.c | 140 ++++++++++++++++++++++++-------------------------
 1 file changed, 69 insertions(+), 71 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index ccc21c6708..b8db056f37 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -2358,7 +2358,7 @@ int write_commit_graph(struct object_directory *odb,
 		       const struct commit_graph_opts *opts)
 {
 	struct repository *r = the_repository;
-	struct write_commit_graph_context *ctx;
+	struct write_commit_graph_context ctx;
 	uint32_t i;
 	int res = 0;
 	int replace = 0;
@@ -2379,16 +2379,16 @@ int write_commit_graph(struct object_directory *odb,
 		return 0;
 	}
 
-	CALLOC_ARRAY(ctx, 1);
-	ctx->r = r;
-	ctx->odb = odb;
-	ctx->append = flags & COMMIT_GRAPH_WRITE_APPEND ? 1 : 0;
-	ctx->report_progress = flags & COMMIT_GRAPH_WRITE_PROGRESS ? 1 : 0;
-	ctx->split = flags & COMMIT_GRAPH_WRITE_SPLIT ? 1 : 0;
-	ctx->opts = opts;
-	ctx->total_bloom_filter_data_size = 0;
-	ctx->write_generation_data = (get_configured_generation_version(r) == 2);
-	ctx->num_generation_data_overflows = 0;
+	memset(&ctx, 0, sizeof(ctx));
+	ctx.r = r;
+	ctx.odb = odb;
+	ctx.append = flags & COMMIT_GRAPH_WRITE_APPEND ? 1 : 0;
+	ctx.report_progress = flags & COMMIT_GRAPH_WRITE_PROGRESS ? 1 : 0;
+	ctx.split = flags & COMMIT_GRAPH_WRITE_SPLIT ? 1 : 0;
+	ctx.opts = opts;
+	ctx.total_bloom_filter_data_size = 0;
+	ctx.write_generation_data = (get_configured_generation_version(r) == 2);
+	ctx.num_generation_data_overflows = 0;
 
 	bloom_settings.hash_version = r->settings.commit_graph_changed_paths_version == 2
 		? 2 : 1;
@@ -2398,14 +2398,14 @@ int write_commit_graph(struct object_directory *odb,
 						  bloom_settings.num_hashes);
 	bloom_settings.max_changed_paths = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS",
 							 bloom_settings.max_changed_paths);
-	ctx->bloom_settings = &bloom_settings;
+	ctx.bloom_settings = &bloom_settings;
 
 	init_topo_level_slab(&topo_levels);
-	ctx->topo_levels = &topo_levels;
+	ctx.topo_levels = &topo_levels;
 
-	prepare_commit_graph(ctx->r);
-	if (ctx->r->objects->commit_graph) {
-		struct commit_graph *g = ctx->r->objects->commit_graph;
+	prepare_commit_graph(ctx.r);
+	if (ctx.r->objects->commit_graph) {
+		struct commit_graph *g = ctx.r->objects->commit_graph;
 
 		while (g) {
 			g->topo_levels = &topo_levels;
@@ -2414,128 +2414,126 @@ int write_commit_graph(struct object_directory *odb,
 	}
 
 	if (flags & COMMIT_GRAPH_WRITE_BLOOM_FILTERS)
-		ctx->changed_paths = 1;
+		ctx.changed_paths = 1;
 	if (!(flags & COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS)) {
 		struct commit_graph *g;
 
-		g = ctx->r->objects->commit_graph;
+		g = ctx.r->objects->commit_graph;
 
 		/* We have changed-paths already. Keep them in the next graph */
 		if (g && g->bloom_filter_settings) {
-			ctx->changed_paths = 1;
-			ctx->bloom_settings = g->bloom_filter_settings;
+			ctx.changed_paths = 1;
+			ctx.bloom_settings = g->bloom_filter_settings;
 		}
 	}
 
-	if (ctx->split) {
-		struct commit_graph *g = ctx->r->objects->commit_graph;
+	if (ctx.split) {
+		struct commit_graph *g = ctx.r->objects->commit_graph;
 
 		while (g) {
-			ctx->num_commit_graphs_before++;
+			ctx.num_commit_graphs_before++;
 			g = g->base_graph;
 		}
 
-		if (ctx->num_commit_graphs_before) {
-			ALLOC_ARRAY(ctx->commit_graph_filenames_before, ctx->num_commit_graphs_before);
-			i = ctx->num_commit_graphs_before;
-			g = ctx->r->objects->commit_graph;
+		if (ctx.num_commit_graphs_before) {
+			ALLOC_ARRAY(ctx.commit_graph_filenames_before, ctx.num_commit_graphs_before);
+			i = ctx.num_commit_graphs_before;
+			g = ctx.r->objects->commit_graph;
 
 			while (g) {
-				ctx->commit_graph_filenames_before[--i] = xstrdup(g->filename);
+				ctx.commit_graph_filenames_before[--i] = xstrdup(g->filename);
 				g = g->base_graph;
 			}
 		}
 
-		if (ctx->opts)
-			replace = ctx->opts->split_flags & COMMIT_GRAPH_SPLIT_REPLACE;
+		if (ctx.opts)
+			replace = ctx.opts->split_flags & COMMIT_GRAPH_SPLIT_REPLACE;
 	}
 
-	ctx->approx_nr_objects = repo_approximate_object_count(the_repository);
+	ctx.approx_nr_objects = repo_approximate_object_count(the_repository);
 
-	if (ctx->append && ctx->r->objects->commit_graph) {
-		struct commit_graph *g = ctx->r->objects->commit_graph;
+	if (ctx.append && ctx.r->objects->commit_graph) {
+		struct commit_graph *g = ctx.r->objects->commit_graph;
 		for (i = 0; i < g->num_commits; i++) {
 			struct object_id oid;
 			oidread(&oid, g->chunk_oid_lookup + g->hash_len * i);
-			oid_array_append(&ctx->oids, &oid);
+			oid_array_append(&ctx.oids, &oid);
 		}
 	}
 
 	if (pack_indexes) {
-		ctx->order_by_pack = 1;
-		if ((res = fill_oids_from_packs(ctx, pack_indexes)))
+		ctx.order_by_pack = 1;
+		if ((res = fill_oids_from_packs(&ctx, pack_indexes)))
 			goto cleanup;
 	}
 
 	if (commits) {
-		if ((res = fill_oids_from_commits(ctx, commits)))
+		if ((res = fill_oids_from_commits(&ctx, commits)))
 			goto cleanup;
 	}
 
 	if (!pack_indexes && !commits) {
-		ctx->order_by_pack = 1;
-		fill_oids_from_all_packs(ctx);
+		ctx.order_by_pack = 1;
+		fill_oids_from_all_packs(&ctx);
 	}
 
-	close_reachable(ctx);
+	close_reachable(&ctx);
 
-	copy_oids_to_commits(ctx);
+	copy_oids_to_commits(&ctx);
 
-	if (ctx->commits.nr >= GRAPH_EDGE_LAST_MASK) {
+	if (ctx.commits.nr >= GRAPH_EDGE_LAST_MASK) {
 		error(_("too many commits to write graph"));
 		res = -1;
 		goto cleanup;
 	}
 
-	if (!ctx->commits.nr && !replace)
+	if (!ctx.commits.nr && !replace)
 		goto cleanup;
 
-	if (ctx->split) {
-		split_graph_merge_strategy(ctx);
+	if (ctx.split) {
+		split_graph_merge_strategy(&ctx);
 
 		if (!replace)
-			merge_commit_graphs(ctx);
+			merge_commit_graphs(&ctx);
 	} else
-		ctx->num_commit_graphs_after = 1;
+		ctx.num_commit_graphs_after = 1;
 
-	ctx->trust_generation_numbers = validate_mixed_generation_chain(ctx->r->objects->commit_graph);
+	ctx.trust_generation_numbers = validate_mixed_generation_chain(ctx.r->objects->commit_graph);
 
-	compute_topological_levels(ctx);
-	if (ctx->write_generation_data)
-		compute_generation_numbers(ctx);
+	compute_topological_levels(&ctx);
+	if (ctx.write_generation_data)
+		compute_generation_numbers(&ctx);
 
-	if (ctx->changed_paths)
-		compute_bloom_filters(ctx);
+	if (ctx.changed_paths)
+		compute_bloom_filters(&ctx);
 
-	res = write_commit_graph_file(ctx);
+	res = write_commit_graph_file(&ctx);
 
-	if (ctx->split)
-		mark_commit_graphs(ctx);
+	if (ctx.split)
+		mark_commit_graphs(&ctx);
 
-	expire_commit_graphs(ctx);
+	expire_commit_graphs(&ctx);
 
 cleanup:
-	free(ctx->graph_name);
-	free(ctx->commits.list);
-	oid_array_clear(&ctx->oids);
+	free(ctx.graph_name);
+	free(ctx.commits.list);
+	oid_array_clear(&ctx.oids);
 	clear_topo_level_slab(&topo_levels);
 
-	if (ctx->commit_graph_filenames_after) {
-		for (i = 0; i < ctx->num_commit_graphs_after; i++) {
-			free(ctx->commit_graph_filenames_after[i]);
-			free(ctx->commit_graph_hash_after[i]);
+	if (ctx.commit_graph_filenames_after) {
+		for (i = 0; i < ctx.num_commit_graphs_after; i++) {
+			free(ctx.commit_graph_filenames_after[i]);
+			free(ctx.commit_graph_hash_after[i]);
 		}
 
-		for (i = 0; i < ctx->num_commit_graphs_before; i++)
-			free(ctx->commit_graph_filenames_before[i]);
+		for (i = 0; i < ctx.num_commit_graphs_before; i++)
+			free(ctx.commit_graph_filenames_before[i]);
 
-		free(ctx->commit_graph_filenames_after);
-		free(ctx->commit_graph_filenames_before);
-		free(ctx->commit_graph_hash_after);
+		free(ctx.commit_graph_filenames_after);
+		free(ctx.commit_graph_filenames_before);
+		free(ctx.commit_graph_hash_after);
 	}
 
-	free(ctx);
-
 	return res;
 }
 
-- 
2.42.0.rc0.376.g66bfc4f195
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