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From: Josh Steadmon <steadmon@google.com>
To: git@vger.kernel.org
Cc: gitster@pobox.com, stolee@gmail.com, avarab@gmail.com,
	peff@peff.net, szeder.dev@gmail.com
Subject: [PATCH v6 1/3] commit-graph, fuzz: Add fuzzer for commit-graph
Date: Tue, 15 Jan 2019 14:25:50 -0800	[thread overview]
Message-ID: <c4ec3fc3fc504c1d639845ea409108bb8f0b6d68.1547590928.git.steadmon@google.com> (raw)
In-Reply-To: <cover.1547590928.git.steadmon@google.com>

Break load_commit_graph_one() into a new function, parse_commit_graph().
The latter function operates on arbitrary buffers, which makes it
suitable as a fuzzing target. Since parse_commit_graph() is only called
by load_commit_graph_one() (and the fuzzer described below), we omit
error messages that would be duplicated by the caller.

Adds fuzz-commit-graph.c, which provides a fuzzing entry point
compatible with libFuzzer (and possibly other fuzzing engines).

Signed-off-by: Josh Steadmon <steadmon@google.com>
---
 .gitignore          |  1 +
 Makefile            |  1 +
 commit-graph.c      | 53 ++++++++++++++++++++++++++++++---------------
 commit-graph.h      |  3 +++
 fuzz-commit-graph.c | 16 ++++++++++++++
 5 files changed, 57 insertions(+), 17 deletions(-)
 create mode 100644 fuzz-commit-graph.c

diff --git a/.gitignore b/.gitignore
index 0d77ea5894..8bcf153ed9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+/fuzz-commit-graph
 /fuzz_corpora
 /fuzz-pack-headers
 /fuzz-pack-idx
diff --git a/Makefile b/Makefile
index 1a44c811aa..6b72f37c29 100644
--- a/Makefile
+++ b/Makefile
@@ -684,6 +684,7 @@ SCRIPTS = $(SCRIPT_SH_INS) \
 
 ETAGS_TARGET = TAGS
 
+FUZZ_OBJS += fuzz-commit-graph.o
 FUZZ_OBJS += fuzz-pack-headers.o
 FUZZ_OBJS += fuzz-pack-idx.o
 
diff --git a/commit-graph.c b/commit-graph.c
index 40c855f185..07dd410f3c 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -84,16 +84,10 @@ static int commit_graph_compatible(struct repository *r)
 struct commit_graph *load_commit_graph_one(const char *graph_file)
 {
 	void *graph_map;
-	const unsigned char *data, *chunk_lookup;
 	size_t graph_size;
 	struct stat st;
-	uint32_t i;
-	struct commit_graph *graph;
+	struct commit_graph *ret;
 	int fd = git_open(graph_file);
-	uint64_t last_chunk_offset;
-	uint32_t last_chunk_id;
-	uint32_t graph_signature;
-	unsigned char graph_version, hash_version;
 
 	if (fd < 0)
 		return NULL;
@@ -108,27 +102,55 @@ struct commit_graph *load_commit_graph_one(const char *graph_file)
 		die(_("graph file %s is too small"), graph_file);
 	}
 	graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	ret = parse_commit_graph(graph_map, fd, graph_size);
+
+	if (!ret) {
+		munmap(graph_map, graph_size);
+		close(fd);
+		exit(1);
+	}
+
+	return ret;
+}
+
+struct commit_graph *parse_commit_graph(void *graph_map, int fd,
+					size_t graph_size)
+{
+	const unsigned char *data, *chunk_lookup;
+	uint32_t i;
+	struct commit_graph *graph;
+	uint64_t last_chunk_offset;
+	uint32_t last_chunk_id;
+	uint32_t graph_signature;
+	unsigned char graph_version, hash_version;
+
+	if (!graph_map)
+		return NULL;
+
+	if (graph_size < GRAPH_MIN_SIZE)
+		return NULL;
+
 	data = (const unsigned char *)graph_map;
 
 	graph_signature = get_be32(data);
 	if (graph_signature != GRAPH_SIGNATURE) {
 		error(_("graph signature %X does not match signature %X"),
 		      graph_signature, GRAPH_SIGNATURE);
-		goto cleanup_fail;
+		return NULL;
 	}
 
 	graph_version = *(unsigned char*)(data + 4);
 	if (graph_version != GRAPH_VERSION) {
 		error(_("graph version %X does not match version %X"),
 		      graph_version, GRAPH_VERSION);
-		goto cleanup_fail;
+		return NULL;
 	}
 
 	hash_version = *(unsigned char*)(data + 5);
 	if (hash_version != GRAPH_OID_VERSION) {
 		error(_("hash version %X does not match version %X"),
 		      hash_version, GRAPH_OID_VERSION);
-		goto cleanup_fail;
+		return NULL;
 	}
 
 	graph = alloc_commit_graph();
@@ -152,7 +174,8 @@ struct commit_graph *load_commit_graph_one(const char *graph_file)
 		if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
 			error(_("improper chunk offset %08x%08x"), (uint32_t)(chunk_offset >> 32),
 			      (uint32_t)chunk_offset);
-			goto cleanup_fail;
+			free(graph);
+			return NULL;
 		}
 
 		switch (chunk_id) {
@@ -187,7 +210,8 @@ struct commit_graph *load_commit_graph_one(const char *graph_file)
 
 		if (chunk_repeated) {
 			error(_("chunk id %08x appears multiple times"), chunk_id);
-			goto cleanup_fail;
+			free(graph);
+			return NULL;
 		}
 
 		if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
@@ -201,11 +225,6 @@ struct commit_graph *load_commit_graph_one(const char *graph_file)
 	}
 
 	return graph;
-
-cleanup_fail:
-	munmap(graph_map, graph_size);
-	close(fd);
-	exit(1);
 }
 
 static void prepare_commit_graph_one(struct repository *r, const char *obj_dir)
diff --git a/commit-graph.h b/commit-graph.h
index 9db40b4d3a..813e7c19f1 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -54,6 +54,9 @@ struct commit_graph {
 
 struct commit_graph *load_commit_graph_one(const char *graph_file);
 
+struct commit_graph *parse_commit_graph(void *graph_map, int fd,
+					size_t graph_size);
+
 /*
  * Return 1 if and only if the repository has a commit-graph
  * file and generation numbers are computed in that file.
diff --git a/fuzz-commit-graph.c b/fuzz-commit-graph.c
new file mode 100644
index 0000000000..cf790c9d04
--- /dev/null
+++ b/fuzz-commit-graph.c
@@ -0,0 +1,16 @@
+#include "commit-graph.h"
+
+struct commit_graph *parse_commit_graph(void *graph_map, int fd,
+					size_t graph_size);
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+	struct commit_graph *g;
+
+	g = parse_commit_graph((void *)data, -1, size);
+	free(g);
+
+	return 0;
+}
-- 
2.20.1.97.g81188d93c3-goog


  reply	other threads:[~2019-01-15 22:26 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-05 22:32 [PATCH 0/2] Add commit-graph fuzzer and fix buffer overflow Josh Steadmon
2018-12-05 22:32 ` [PATCH 1/2] commit-graph, fuzz: Add fuzzer for commit-graph Josh Steadmon
2018-12-05 22:48   ` Ævar Arnfjörð Bjarmason
2018-12-06  1:00     ` Josh Steadmon
2018-12-06  1:32   ` Junio C Hamano
2018-12-06  1:41     ` Junio C Hamano
2018-12-06  4:47   ` Junio C Hamano
2018-12-05 22:32 ` [PATCH 2/2] commit-graph: fix buffer read-overflow Josh Steadmon
2018-12-06 13:11   ` Derrick Stolee
2018-12-06 20:20 ` [PATCH v2 0/3] Add commit-graph fuzzer and fix buffer overflow Josh Steadmon
2018-12-06 20:20   ` [PATCH v2 1/3] commit-graph, fuzz: Add fuzzer for commit-graph Josh Steadmon
2018-12-06 20:20   ` [PATCH v2 2/3] commit-graph: fix buffer read-overflow Josh Steadmon
2018-12-07  9:07     ` Jeff King
2018-12-07 13:33     ` Derrick Stolee
2018-12-06 20:20   ` [PATCH v2 3/3] Makefile: correct example fuzz build Josh Steadmon
2018-12-07 22:27   ` [PATCH v3 0/3] Add commit-graph fuzzer and fix buffer overflow Josh Steadmon
2018-12-07 22:27     ` [PATCH v3 1/3] commit-graph, fuzz: Add fuzzer for commit-graph Josh Steadmon
2018-12-07 22:27     ` [PATCH v3 2/3] commit-graph: fix buffer read-overflow Josh Steadmon
2018-12-09  4:01       ` Junio C Hamano
2018-12-10  4:28         ` SZEDER Gábor
2018-12-10 21:58           ` Josh Steadmon
2018-12-10 21:56         ` Josh Steadmon
2018-12-11  9:50           ` Jeff King
2018-12-07 22:27     ` [PATCH v3 3/3] Makefile: correct example fuzz build Josh Steadmon
2018-12-13 19:43 ` [PATCH v4 0/3] Add commit-graph fuzzer and fix buffer overflow Josh Steadmon
2018-12-13 19:43   ` [PATCH v4 1/3] commit-graph, fuzz: Add fuzzer for commit-graph Josh Steadmon
2018-12-13 19:43   ` [PATCH v4 2/3] commit-graph: fix buffer read-overflow Josh Steadmon
2019-01-12 10:57     ` SZEDER Gábor
2019-01-15 19:58       ` Josh Steadmon
2018-12-13 19:43   ` [PATCH v4 3/3] Makefile: correct example fuzz build Josh Steadmon
2018-12-18 17:35   ` [PATCH v4 0/3] Add commit-graph fuzzer and fix buffer overflow Jeff King
2018-12-18 21:05     ` Josh Steadmon
2018-12-19 15:51       ` Jeff King
2018-12-20 19:35         ` Johannes Schindelin
2018-12-20 20:11           ` Jeff King
2018-12-26 22:29         ` Junio C Hamano
2019-01-15 19:59 ` [PATCH v5 " Josh Steadmon
2019-01-15 19:59   ` [PATCH v5 1/3] commit-graph, fuzz: Add fuzzer for commit-graph Josh Steadmon
2019-01-15 20:33     ` Junio C Hamano
2019-01-15 19:59   ` [PATCH v5 2/3] commit-graph: fix buffer read-overflow Josh Steadmon
2019-01-15 19:59   ` [PATCH v5 3/3] Makefile: correct example fuzz build Josh Steadmon
2019-01-15 20:39     ` Junio C Hamano
2019-01-15 21:59       ` Josh Steadmon
2019-01-15 22:34         ` Junio C Hamano
2019-01-15 22:25 ` [PATCH v6 0/3] Add commit-graph fuzzer and fix buffer overflow Josh Steadmon
2019-01-15 22:25   ` Josh Steadmon [this message]
2019-01-15 22:25   ` [PATCH v6 2/3] commit-graph: fix buffer read-overflow Josh Steadmon
2019-02-20 14:55     ` Ævar Arnfjörð Bjarmason
2019-02-20 16:50       ` SZEDER Gábor
2019-01-15 22:25   ` [PATCH v6 3/3] Makefile: correct example fuzz build Josh Steadmon

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