On 11/3/2018 10:27 PM, Jeff King wrote:
On Sat, Nov 03, 2018 at 05:49:57PM -0700, Carlo Marcelo Arenas Belón wrote:introduced in 662148c435 ("midx: write object offsets", 2018-07-12) but included on all previous versions as well. midx.c:713:54: warning: unused parameter 'nr_objects' [-Wunused-parameter] likely an oversight as the information needed to iterate over is embedded in nr_large_offsetI've been preparing a series to make the whole code base compile with -Wunused-parameter, and I handled this case a bit differently. -- >8 -- Subject: [PATCH] midx: double-check large object write loop The write_midx_large_offsets() function takes an array of object entries, the number of entries in the array (nr_objects), and the number of entries with large offsets (nr_large_offset). But we never actually use nr_objects; instead we keep walking down the array and counting down nr_large_offset until we've seen all of the large entries. This is correct, but we can be a bit more defensive. If there were ever a mismatch between nr_large_offset and the actual set of large-offset objects, we'd walk off the end of the array. Since we know the size of the array, we can use nr_objects to make sure we don't walk too far. Signed-off-by: Jeff King <p...@peff.net>
Thanks, both, for catching this. I prefer the approach that adds defenses. Reviewed-by: Derrick Stolee <dsto...@microsoft.com>
--- midx.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/midx.c b/midx.c index 4fac0cd08a..ecd583666a 100644 --- a/midx.c +++ b/midx.c @@ -712,12 +712,18 @@ static size_t write_midx_object_offsets(struct hashfile *f, int large_offset_nee static size_t write_midx_large_offsets(struct hashfile *f, uint32_t nr_large_offset, struct pack_midx_entry *objects, uint32_t nr_objects) { - struct pack_midx_entry *list = objects; + struct pack_midx_entry *list = objects, *end = objects + nr_objects; size_t written = 0;while (nr_large_offset) {- struct pack_midx_entry *obj = list++; - uint64_t offset = obj->offset; + struct pack_midx_entry *obj; + uint64_t offset; + + if (list >= end) + BUG("too many large-offset objects"); + + obj = list++; + offset = obj->offset;if (!(offset >> 31))continue;
