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| author | Liang Chen <liangchen.linux@gmail.com> | 2017-10-14 01:35:40 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-10-16 17:07:26 +0200 |
| commit | 6446c684f9418d0175c9c3e5134e7744fe79181a (patch) | |
| tree | 0ecab99341033e1f332c05eddd6d0abbb17e19a7 /drivers/md | |
| parent | bcache: rearrange writeback main thread ratelimit (diff) | |
| download | linux-6446c684f9418d0175c9c3e5134e7744fe79181a.tar.xz linux-6446c684f9418d0175c9c3e5134e7744fe79181a.zip | |
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 <liangchen.linux@gmail.com>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/bcache/closure.h | 6 |
1 files changed, 6 insertions, 0 deletions
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)); |