Messages in this thread | | | Date | Tue, 14 Dec 2021 17:12:48 +0800 | Subject | Re: [PATCH -next] blk-throttle: Set BIO_THROTTLED when bio has been throttled | From | QiuLaibin <> |
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On 2021/12/14 4:12, Tejun Heo wrote: > On Mon, Dec 13, 2021 at 05:24:00PM +0800, QiuLaibin wrote: >>> * This function is called synchronously on the issue path. The bio isn't >>> seen by the queue and device driver yet and nothing can race to issue it >>> before this function returns. >>> >> >> The bio is under throttle here, this submit_bio return directly. And >> current process will queue a dispatch work by >> throtl_schedule_pending_timer() to submit this bio before BIO_THROTTLED flag >> set. If the bio is completed quickly after the dispatch work is queued, UAF >> of bio will happen. > > You are right, the timer can get to it. Can't it be solved by just > reordering spin_unlock and setting BIO_THROTTLED? >
I think it can be solved by setting BIO_THROTTLED before queue dispatch work.
>>> * Now we're not setting BIO_THROTTLED when we're taking a different return >>> path through the out_unlock label and risks calling back into blk_throtl >>> again on the same bio. >>> >> >> In my opinion, This flag can prevent the request from being throttled >> multiple times. If the request itself does not need to be throttled, the >> result of repeated entry will be the same. >> If necessary, I think we can use other methods to achieve this effect for >> request does not need to be throttled. > > So that we don't change anything regarding this? >
I am thinking of adding a new bio tag (like BIO_THROTTLE_BYPASS) to avoid those requests which do not need to be throttled to enter the throttle multiple times. > Thanks. >
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