From 6446c684f9418d0175c9c3e5134e7744fe79181a Mon Sep 17 00:00:00 2001 From: Liang Chen Date: Fri, 13 Oct 2017 16:35:40 -0700 Subject: [PATCH] bcache: safeguard a dangerous addressing in closure_queue The use of the union reduces the size of closure struct by taking advantage of the current size of its members. The offset of func in work_struct equals the size of the first three members, so that work.work_func will just reference the forth member - fn. This is smart but dangerous. It can be broken if work_struct or the other structs get changed, and can be a bit difficult to debug. Signed-off-by: Liang Chen Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe --- drivers/md/bcache/closure.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h index 295b7e43f92c..00fb314cce57 100644 --- a/drivers/md/bcache/closure.h +++ b/drivers/md/bcache/closure.h @@ -251,6 +251,12 @@ static inline void set_closure_fn(struct closure *cl, closure_fn *fn, static inline void closure_queue(struct closure *cl) { struct workqueue_struct *wq = cl->wq; + /** + * Changes made to closure, work_struct, or a couple of other structs + * may cause work.func not pointing to the right location. + */ + BUILD_BUG_ON(offsetof(struct closure, fn) + != offsetof(struct work_struct, func)); if (wq) { INIT_WORK(&cl->work, cl->work.func); BUG_ON(!queue_work(wq, &cl->work));