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[104.178.186.189]) by smtp.gmail.com with ESMTPSA id m12-20020a0cf18c000000b0065b02eaeee7sm5228467qvl.83.2023.10.10.18.24.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Oct 2023 18:24:43 -0700 (PDT) Date: Tue, 10 Oct 2023 21:24:39 -0400 From: Taylor Blau To: Jeff King Cc: git@vger.kernel.org Subject: Re: [PATCH 04/20] commit-graph: check size of oid fanout chunk Message-ID: References: <20231009205544.GA3281950@coredump.intra.peff.net> <20231009205951.GD3282181@coredump.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org 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.