Merge branch 'tb/commit-graph-fd-exhaustion-fix'

The commit-graph code exhausted file descriptors easily when it
does not have to.

* tb/commit-graph-fd-exhaustion-fix:
  commit-graph: close descriptors after mmap
  commit-graph.c: gracefully handle file descriptor exhaustion
  t/test-lib.sh: make ULIMIT_FILE_DESCRIPTORS available to tests
  commit-graph.c: don't use discarded graph_name in error

6 files changed, 33 insertions, 29 deletions

diff --git a/commit-graph.c b/commit-graph.c
index d11c836e1f..e9b3c5d561 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -69,7 +69,6 @@ static uint8_t oid_version(void)
 static struct commit_graph *alloc_commit_graph(void)
 {
 	struct commit_graph *g = xcalloc(1, sizeof(*g));
-	g->graph_fd = -1;
 
 	return g;
 }
@@ -123,14 +122,13 @@ struct commit_graph *load_commit_graph_one_fd_st(int fd, struct stat *st,
 		return NULL;
 	}
 	graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
-	ret = parse_commit_graph(graph_map, fd, graph_size);
+	close(fd);
+	ret = parse_commit_graph(graph_map, graph_size);
 
 	if (ret)
 		ret->odb = odb;
-	else {
+	else
 		munmap(graph_map, graph_size);
-		close(fd);
-	}
 
 	return ret;
 }
@@ -165,8 +163,7 @@ static int verify_commit_graph_lite(struct commit_graph *g)
 	return 0;
 }
 
-struct commit_graph *parse_commit_graph(void *graph_map, int fd,
-					size_t graph_size)
+struct commit_graph *parse_commit_graph(void *graph_map, size_t graph_size)
 {
 	const unsigned char *data, *chunk_lookup;
 	uint32_t i;
@@ -209,7 +206,6 @@ struct commit_graph *parse_commit_graph(void *graph_map, int fd,
 
 	graph->hash_len = the_hash_algo->rawsz;
 	graph->num_chunks = *(unsigned char*)(data + 6);
-	graph->graph_fd = fd;
 	graph->data = graph_map;
 	graph->data_len = graph_size;
 
@@ -1397,7 +1393,7 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
 
 		fd = git_mkstemp_mode(ctx->graph_name, 0444);
 		if (fd < 0) {
-			error(_("unable to create '%s'"), ctx->graph_name);
+			error(_("unable to create temporary graph layer"));
 			return -1;
 		}
 
@@ -1602,8 +1598,8 @@ static void split_graph_merge_strategy(struct write_commit_graph_context *ctx)
 		free(old_graph_name);
 	}
 
-	ALLOC_ARRAY(ctx->commit_graph_filenames_after, ctx->num_commit_graphs_after);
-	ALLOC_ARRAY(ctx->commit_graph_hash_after, ctx->num_commit_graphs_after);
+	CALLOC_ARRAY(ctx->commit_graph_filenames_after, ctx->num_commit_graphs_after);
+	CALLOC_ARRAY(ctx->commit_graph_hash_after, ctx->num_commit_graphs_after);
 
 	for (i = 0; i < ctx->num_commit_graphs_after &&
 		    i < ctx->num_commit_graphs_before; i++)
@@ -2125,10 +2121,9 @@ void free_commit_graph(struct commit_graph *g)
 {
 	if (!g)
 		return;
-	if (g->graph_fd >= 0) {
+	if (g->data) {
 		munmap((void *)g->data, g->data_len);
 		g->data = NULL;
-		close(g->graph_fd);
 	}
 	free(g->filename);
 	free(g);
diff --git a/commit-graph.h b/commit-graph.h
index 98ef121924..1254eae948 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -40,8 +40,6 @@ struct tree *get_commit_tree_in_graph(struct repository *r,
 				      const struct commit *c);
 
 struct commit_graph {
-	int graph_fd;
-
 	const unsigned char *data;
 	size_t data_len;
 
@@ -66,8 +64,7 @@ struct commit_graph *load_commit_graph_one_fd_st(int fd, struct stat *st,
 						 struct object_directory *odb);
 struct commit_graph *read_commit_graph_one(struct repository *r,
 					   struct object_directory *odb);
-struct commit_graph *parse_commit_graph(void *graph_map, int fd,
-					size_t graph_size);
+struct commit_graph *parse_commit_graph(void *graph_map, size_t graph_size);
 
 /*
  * Return 1 if and only if the repository has a commit-graph
diff --git a/fuzz-commit-graph.c b/fuzz-commit-graph.c
index 0157acbf2e..9fd1c04edd 100644
--- a/fuzz-commit-graph.c
+++ b/fuzz-commit-graph.c
@@ -1,8 +1,7 @@
 #include "commit-graph.h"
 #include "repository.h"
 
-struct commit_graph *parse_commit_graph(void *graph_map, int fd,
-					size_t graph_size);
+struct commit_graph *parse_commit_graph(void *graph_map, size_t graph_size);
 
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
 
@@ -11,7 +10,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 	struct commit_graph *g;
 
 	initialize_the_repository();
-	g = parse_commit_graph((void *)data, -1, size);
+	g = parse_commit_graph((void *)data, size);
 	repo_clear(the_repository);
 	free(g);
 
diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index 48d0d42afd..e1197ac818 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -1354,15 +1354,6 @@ test_expect_success 'fails with duplicate ref update via symref' '
 	test_cmp expect actual
 '
 
-run_with_limited_open_files () {
-	(ulimit -n 32 && "$@")
-}
-
-test_lazy_prereq ULIMIT_FILE_DESCRIPTORS '
-	test_have_prereq !MINGW,!CYGWIN &&
-	run_with_limited_open_files true
-'
-
 test_expect_success ULIMIT_FILE_DESCRIPTORS 'large transaction creating branches does not burst open file limit' '
 (
 	for i in $(test_seq 33)
diff --git a/t/t5324-split-commit-graph.sh b/t/t5324-split-commit-graph.sh
index 3378ec54cd..4146b82031 100755
--- a/t/t5324-split-commit-graph.sh
+++ b/t/t5324-split-commit-graph.sh
@@ -387,4 +387,17 @@ test_expect_success '--split=replace replaces the chain' '
 	graph_read_expect 2
 '
 
+test_expect_success ULIMIT_FILE_DESCRIPTORS 'handles file descriptor exhaustion' '
+	git init ulimit &&
+	(
+		cd ulimit &&
+		for i in $(test_seq 64)
+		do
+			test_commit $i &&
+			test_might_fail run_with_limited_open_files git commit-graph write \
+				--split=no-merge --reachable || return 1
+		done
+	)
+'
+
 test_done
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 13ba00d508..1b221951a8 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1666,6 +1666,15 @@ test_lazy_prereq ULIMIT_STACK_SIZE '
 	run_with_limited_stack true
 '
 
+run_with_limited_open_files () {
+	(ulimit -n 32 && "$@")
+}
+
+test_lazy_prereq ULIMIT_FILE_DESCRIPTORS '
+	test_have_prereq !MINGW,!CYGWIN &&
+	run_with_limited_open_files true
+'
+
 build_option () {
 	git version --build-options |
 	sed -ne "s/^$1: //p"