block: make bioset_exit() fully resilient against being called twice

[ Upstream commit 605f7415ecfb426610195dd6c7577b30592b3369 ]

Most of bioset_exit() is fine being called twice, as it clears the
various allocations etc when they are freed. The exception is
bio_alloc_cache_destroy(), which does not clear ->cache when it has
freed it.

This isn't necessarily a bug, but can be if buggy users does call the
exit path more then once, or with just a memset() bioset which has
never been initialized. dm appears to be one such user.

Fixes: be4d234d7aeb ("bio: add allocation cache abstraction")
Link: https://lore.kernel.org/linux-block/YpK7m+14A+pZKs5k@casper.infradead.org/
Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/block/bio.c b/block/bio.c
index 9b28381..8381c66 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -665,6 +665,7 @@ static void bio_alloc_cache_destroy(struct bio_set *bs)
                bio_alloc_cache_prune(cache, -1U);
        }
        free_percpu(bs->cache);
+       bs->cache = NULL;
 }
 
 /**