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authorLiang Chen <liangchen.linux@gmail.com>2017-10-14 02:35:40 +0300
committerJens Axboe <axboe@kernel.dk>2017-10-16 18:07:26 +0300
commit6446c684f9418d0175c9c3e5134e7744fe79181a (patch)
tree0ecab99341033e1f332c05eddd6d0abbb17e19a7
parenta8500fc816b19795756d27c762daa5e19f5e1b6f (diff)
downloadlinux-6446c684f9418d0175c9c3e5134e7744fe79181a.tar.xz
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>
-rw-r--r--drivers/md/bcache/closure.h6
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));