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bcache: fix variable length array abuse in btree_iter

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btree_iter is used in two ways: either allocated on the stack with a
fixed size MAX_BSETS, or from a mempool with a dynamic size based on the
specific cache set. Previously, the struct had a fixed-length array of
size MAX_BSETS which was indexed out-of-bounds for the dynamically-sized
iterators, which causes UBSAN to complain.

This patch uses the same approach as in bcachefs's sort_iter and splits
the iterator into a btree_iter with a flexible array member and a
btree_iter_stack which embeds a btree_iter as well as a fixed-length
data array.

Cc: stable@vger.kernel.org
Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039368
Signed-off-by: Matthew Mirvish <matthew@mm12.xyz>
Signed-off-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20240509011117.2697-3-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Matthew Mirvish
2024-05-09 09:11:17 +08:00
committed by Jens Axboe
parent 2abd9a197d
commit 3a861560cc
6 changed files with 70 additions and 59 deletions
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5
drivers/md/bcache/super.c
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@@ -1914,8 +1914,9 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
INIT_LIST_HEAD(&c->btree_cache_freed);
INIT_LIST_HEAD(&c->data_buckets);
iter_size = ((meta_bucket_pages(sb) * PAGE_SECTORS) / sb->block_size + 1) *
sizeof(struct btree_iter_set);
iter_size = sizeof(struct btree_iter) +
((meta_bucket_pages(sb) * PAGE_SECTORS) / sb->block_size) *
sizeof(struct btree_iter_set);
c->devices = kcalloc(c->nr_uuids, sizeof(void *), GFP_KERNEL);
if (!c->devices)