After reading the pseudo-merge extension's metadata table, we allocate
an array to store information about each pseudo-merge, including its
byte offset within the .bitmap file itself.
This is done like so:
pseudo_merge_ofs = index_end - 24 -
(index->pseudo_merges.nr * sizeof(uint64_t));
for (i = 0; i < index->pseudo_merges.nr; i++) {
index->pseudo_merges.v[i].at = get_be64(pseudo_merge_ofs);
pseudo_merge_ofs += sizeof(uint64_t);
}
But if the pseudo-merge table is corrupt, we'll keep calling get_be64()
past the end of the pseudo-merge extension, potentially reading off the
end of the mmap'd region.
Prevent this by ensuring that we have at least `table_size - 24` many
bytes available to read (subtracting 24 as the length of the metadata
component).
This is sufficient to prevent us from reading off the end of the
pseudo-merge extension, and ensures that all of the get_be64() calls
below are in bounds.
Helped-by: Jeff King <peff@xxxxxxxx>
Signed-off-by: Taylor Blau <me@xxxxxxxxxxxx>
---
pack-bitmap.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/pack-bitmap.c b/pack-bitmap.c
index 70230e2647..ad2635c025 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -238,6 +238,9 @@ static int load_bitmap_header(struct bitmap_index *index)
index->pseudo_merges.commits_nr = get_be32(index_end - 20);
index->pseudo_merges.nr = get_be32(index_end - 24);
+ if (st_mult(index->pseudo_merges.nr, sizeof(uint64_t)) > table_size - 24)
+ return error(_("corrupted bitmap index file, pseudo-merge table too short"));
+
CALLOC_ARRAY(index->pseudo_merges.v,
index->pseudo_merges.nr);
--
2.45.0.32.ga71ec05e5dc.dirty
