Messages in this thread Patch in this message | | | From | Liang Chen <> | Subject | [PATCH] bcache: safeguard a dangerous addressing in closure_queue | Date | Thu, 12 Oct 2017 22:37:37 +0800 |
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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 <liangchen.linux@gmail.com> --- Replacing all occurences of closure_fn to work_func_fn seems to be an option but that would end up with a big lenghty and error prone patch.
drivers/md/bcache/closure.h | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h index 295b7e4..dbff8f4 100644 --- a/drivers/md/bcache/closure.h +++ b/drivers/md/bcache/closure.h @@ -251,6 +251,11 @@ 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. + */ + BUG_ON((unsigned long)cl->fn != (unsigned long)cl->work.func); if (wq) { INIT_WORK(&cl->work, cl->work.func); BUG_ON(!queue_work(wq, &cl->work)); -- 1.8.3.1
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