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[PATCH 04/20] midx.c: use `size_t`'s for fanout nr and alloc

From
Taylor Blau <me@ttaylorr.com>
Date
Jul 12, 2023, 23:37 UTC
Message-ID
<bdad7286046e5f4ae43d4b2571fab2d3e31912c7.1689205042.git.me@ttaylorr.com>
In-Reply-To
<cover.1689205042.git.me@ttaylorr.com>

The `midx_fanout` struct is used to keep track of a set of OIDs corresponding to each layer of the MIDX's fanout table. It stores an array of entries, along with the number of entries in the table, and the allocated size of the array.

Both `nr` and `alloc` are stored as 32-bit unsigned integers. In practice, this should never cause any problems, since most packs have far fewer than 2^32-1 objects.

But storing these as `size_t`'s is more appropriate, and prevents us from accidentally overflowing some result when multiplying or adding to either of these values. Update these struct members to be `size_t`'s as appropriate.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 midx.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/midx.c b/midx.c
index db459e448b..449c10289c 100644
--- a/midx.c
+++ b/midx.c
@@ -584,12 +584,14 @@ static void fill_pack_entry(uint32_t pack_int_id,
 
 struct midx_fanout {
 	struct pack_midx_entry *entries;
-	uint32_t nr;
-	uint32_t alloc;
+	size_t nr, alloc;
 };
 
-static void midx_fanout_grow(struct midx_fanout *fanout, uint32_t nr)
+static void midx_fanout_grow(struct midx_fanout *fanout, size_t nr)
 {
+	if (nr < fanout->nr)
+		BUG("negative growth in midx_fanout_grow() (%"PRIuMAX" < %"PRIuMAX")",
+		    (uintmax_t)nr, (uintmax_t)fanout->nr);
 	ALLOC_GROW(fanout->entries, nr, fanout->alloc);
 }
 

-- 
2.41.0.347.g7b976b8871f
Previous: Taylor BlauNext: Taylor Blau
Message 12 of 28 in “guard object lookups against 32-bit overflow”
  1. 00/20 guard object lookups against 32-bit overflowTaylor Blau, Jul 12, 2023
  2. 01/20 packfile.c: prevent overflow in `nth_packed_object_id()`Taylor Blau, Jul 12, 2023
  3. 02/20 packfile.c: prevent overflow in `load_idx()`Taylor Blau, Jul 12, 2023
  4. Phillip WoodJul 13, 2023
  5. Taylor BlauJul 13, 2023
  6. Taylor BlauJul 14, 2023
  7. Phillip WoodJul 14, 2023
  8. Junio C HamanoJul 14, 2023
  9. Phillip WoodJul 14, 2023
  10. Junio C HamanoJul 13, 2023
  11. 03/20 packfile.c: use checked arithmetic in `nth_packed_object_offset()`Taylor Blau, Jul 12, 2023
  12. 04/20 midx.c: use `size_t`'s for fanout nr and allocTaylor Blau, Jul 12, 2023
  13. 05/20 midx.c: prevent overflow in `nth_midxed_object_oid()`Taylor Blau, Jul 12, 2023
  14. 06/20 midx.c: prevent overflow in `nth_midxed_offset()`Taylor Blau, Jul 12, 2023
  15. 08/20 midx.c: prevent overflow in `write_midx_internal()`Taylor Blau, Jul 12, 2023
  16. 09/20 midx.c: prevent overflow in `fill_included_packs_batch()`Taylor Blau, Jul 12, 2023
  17. 10/20 pack-bitmap.c: ensure that eindex lookups don't overflowTaylor Blau, Jul 12, 2023
  18. 11/20 commit-graph.c: prevent overflow in `write_commit_graph_file()`Taylor Blau, Jul 12, 2023
  19. 12/20 commit-graph.c: prevent overflow in add_graph_to_chain()Taylor Blau, Jul 12, 2023
  20. 13/20 commit-graph.c: prevent overflow in `load_oid_from_graph()`Taylor Blau, Jul 12, 2023
  21. 14/20 commit-graph.c: prevent overflow in `fill_commit_graph_info()`Taylor Blau, Jul 12, 2023
  22. 15/20 commit-graph.c: prevent overflow in `fill_commit_in_graph()`Taylor Blau, Jul 12, 2023
  23. 16/20 commit-graph.c: prevent overflow in `load_tree_for_commit()`Taylor Blau, Jul 12, 2023
  24. 17/20 commit-graph.c: prevent overflow in `split_graph_merge_strategy()`Taylor Blau, Jul 12, 2023
  25. 18/20 commit-graph.c: prevent overflow in `merge_commit_graph()`Taylor Blau, Jul 12, 2023
  26. 19/20 commit-graph.c: prevent overflow in `write_commit_graph()`Taylor Blau, Jul 12, 2023
  27. 20/20 commit-graph.c: prevent overflow in `verify_commit_graph()`Taylor Blau, Jul 12, 2023
  28. 07/20 midx.c: store `nr`, `alloc` variables as `size_t`'sTaylor Blau, Jul 12, 2023

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