[PATCH v2 3/3] pack-revindex.c: guard against out-of-bounds pack lookups

The function midx_key_to_pack_pos() is a helper function used by
midx_to_pack_pos() and midx_pair_to_pack_pos() to translate a (pack,
offset) tuple into a position into the MIDX pseudo-pack order.

Ensure that the pack ID given to midx_pair_to_pack_pos() is bounded by
the number of packs within the MIDX to prevent, for instance,
uninitialized memory from being used as a pack ID.

Signed-off-by: Taylor Blau <redacted>
---
 pack-revindex.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pack-revindex.c b/pack-revindex.c
index fc63aa76a2..93ffca7731 100644
--- a/pack-revindex.c
+++ b/pack-revindex.c

@@ -527,6 +527,9 @@ static int midx_key_to_pack_pos(struct multi_pack_index *m,
 {
 	uint32_t *found;
 
+	if (key->pack >= m->num_packs)
+		BUG("MIDX pack lookup out of bounds (%"PRIu32" >= %"PRIu32")",
+		    key->pack, m->num_packs);
 	/*
 	 * The preferred pack sorts first, so determine its identifier by
 	 * looking at the first object in pseudo-pack order.

-- 
2.45.2.448.g06de4005f1