On Tue, Oct 10, 2023 at 08:08:05PM -0400, Taylor Blau wrote:
> Do you think it would be worth changing pair_chunk() to take an expected
> size_t and handle this generically? I.e. have a version of
> chunk-format::pair_chunk_fn() that looks something like:
>
> static int pair_chunk_fn(const unsigned char *chunk_start,
> size_t chunk_size, void *data)
> {
> const unsigned char **p = data;
> if (chunk_size != data->size)
> return -1;
> *p = chunk_start;
> return 0;
> }
>
> and then our call here would be:
>
> if (pair_chunk(cf, GRAPH_CHUNKID_OIDFANOUT,
> (const unsigned char **)&graph->chunk_oid_fanout,
> 256 * sizeof(uint32_t)) < 0)
> return error("commit-graph oid fanout chunk is wrong size");
I took a brief stab at implementing this tonight and came up with this,
which applies on top of this patch. Looking through the rest of the
series briefly[^1], I think having something like this would be useful:
--- 8< ---
diff --git a/chunk-format.c b/chunk-format.c
index 8d910e23f6..38b0f847be 100644
--- a/chunk-format.c
+++ b/chunk-format.c
@@ -157,6 +157,8 @@ int read_table_of_contents(struct chunkfile *cf,
struct pair_chunk_data {
const unsigned char **p;
size_t *size;
+
+ size_t expected_size;
};
static int pair_chunk_fn(const unsigned char *chunk_start,
@@ -169,6 +171,20 @@ static int pair_chunk_fn(const unsigned char *chunk_start,
return 0;
}
+static int pair_chunk_expect_fn(const unsigned char *chunk_start,
+ size_t chunk_size,
+ void *data)
+{
+ struct pair_chunk_data *pcd = data;
+ if (pcd->expected_size != chunk_size)
+ return error(_("mismatched chunk size, got: %"PRIuMAX", wanted:"
+ " %"PRIuMAX),
+ (uintmax_t)chunk_size,
+ (uintmax_t)pcd->expected_size);
+ *pcd->p = chunk_start;
+ return 0;
+}
+
int pair_chunk(struct chunkfile *cf,
uint32_t chunk_id,
const unsigned char **p,
@@ -178,6 +194,14 @@ int pair_chunk(struct chunkfile *cf,
return read_chunk(cf, chunk_id, pair_chunk_fn, &pcd);
}
+int pair_chunk_expect(struct chunkfile *cf,
+ uint32_t chunk_id, const unsigned char **p,
+ size_t expected_size)
+{
+ struct pair_chunk_data pcd = { .p = p, .expected_size = expected_size };
+ return read_chunk(cf, chunk_id, pair_chunk_expect_fn, &pcd);
+}
+
int pair_chunk_unsafe(struct chunkfile *cf,
uint32_t chunk_id,
const unsigned char **p)
diff --git a/chunk-format.h b/chunk-format.h
index 8dce7967f4..778f81f555 100644
--- a/chunk-format.h
+++ b/chunk-format.h
@@ -53,6 +53,10 @@ int pair_chunk(struct chunkfile *cf,
const unsigned char **p,
size_t *size);
+int pair_chunk_expect(struct chunkfile *cf,
+ uint32_t chunk_id, const unsigned char **p,
+ size_t expected_size);
+
/*
* Unsafe version of pair_chunk; it does not return the size,
* meaning that the caller cannot possibly be careful about
diff --git a/commit-graph.c b/commit-graph.c
index 9b3b01da61..ed85161fdb 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -305,16 +305,6 @@ static int verify_commit_graph_lite(struct commit_graph *g)
return 0;
}
-static int graph_read_oid_fanout(const unsigned char *chunk_start,
- size_t chunk_size, void *data)
-{
- struct commit_graph *g = data;
- if (chunk_size != 256 * sizeof(uint32_t))
- return error("commit-graph oid fanout chunk is wrong size");
- g->chunk_oid_fanout = (const uint32_t *)chunk_start;
- return 0;
-}
-
static int graph_read_oid_lookup(const unsigned char *chunk_start,
size_t chunk_size, void *data)
{
@@ -404,7 +394,10 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
GRAPH_HEADER_SIZE, graph->num_chunks))
goto free_and_return;
- read_chunk(cf, GRAPH_CHUNKID_OIDFANOUT, graph_read_oid_fanout, graph);
+ if (pair_chunk_expect(cf, GRAPH_CHUNKID_OIDFANOUT,
+ (const unsigned char **)&graph->chunk_oid_fanout,
+ 256 * sizeof(uint32_t)) < 0)
+ error(_("commit-graph oid fanout chunk is wrong size"));
read_chunk(cf, GRAPH_CHUNKID_OIDLOOKUP, graph_read_oid_lookup, graph);
pair_chunk_unsafe(cf, GRAPH_CHUNKID_DATA, &graph->chunk_commit_data);
pair_chunk_unsafe(cf, GRAPH_CHUNKID_EXTRAEDGES, &graph->chunk_extra_edges);
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index d25bea3ec5..467b5f5e9c 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -841,6 +841,7 @@ test_expect_success 'reader notices too-small oid fanout chunk' '
# otherwise we hit an earlier check
check_corrupt_chunk OIDF clear $(printf "000000%02x" $(test_seq 250)) &&
cat >expect.err <<-\EOF &&
+ error: mismatched chunk size, got: 1000, wanted: 1024
error: commit-graph oid fanout chunk is wrong size
error: commit-graph is missing the OID Fanout chunk
EOF
--- >8 ---
Or, quite honestly, having the "expected_size" parameter be required in
the safe version of `pair_chunk()`.
Thanks,
Taylor
[^1]: A non-brief review is on my to-do list for tomorrow.
