[PATCH] bcache: avoid a dangerous addressing in closure_queue

From: Liang Chen
Date: Wed Jul 05 2017 - 08:53:43 EST

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 - the pointer to closure_fn.

This is smart but dangerous. It can be broken if work_struct or the other
ones get changed, and can be a bit difficult to debug.

Signed-off-by: Liang Chen <liangchen.linux@xxxxxxxxx>
drivers/md/bcache/closure.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h
index 1ec84ca..665c470 100644
--- a/drivers/md/bcache/closure.h
+++ b/drivers/md/bcache/closure.h
@@ -251,8 +251,9 @@ 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;
+ closure_fn *fn = cl->fn;
if (wq) {
- INIT_WORK(&cl->work, cl->work.func);
+ INIT_WORK(&cl->work, (work_func_t)fn);
BUG_ON(!queue_work(wq, &cl->work));
} else