commit-graph, fuzz: add fuzzer for commit-graph

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/.gitignore b/.gitignore
index 0d77ea5894274c43c4b348c8b52b8e665a1a339e..8bcf153ed93f4a5ea9d9e4e2fd27d89316730e09 100644 (file)
--- 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 1a44c811aa56330327172cf693c61f9a221e4e16..6b72f37c29fe4cd5aac9270ccedd63333a44ce4d 100644 (file)
--- 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 5c8fb4b134e96354cb25ea2d5bb060ce77ae3e2b..15afad245a9022a96533a4187ff4cb9af1cd1fec 100644 (file)
--- 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 9db40b4d3aadb75b4dcea5027d07d373bdf169e1..813e7c19f127565c384df456907e654ffe9eafa3 100644 (file)
--- 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 (file)
index 0000000..cf790c9
--- /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;
+}