From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>,
Hao Xu <[email protected]>,
[email protected]
Cc: [email protected]
Subject: Re: [PATCH 3/5] io_uring: let fast poll support multishot
Date: Fri, 6 May 2022 16:02:33 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 5/6/22 11:19 AM, Pavel Begunkov wrote:
> On 5/6/22 08:01, Hao Xu wrote:
>> From: Hao Xu <[email protected]>
>>
>> For operations like accept, multishot is a useful feature, since we can
>> reduce a number of accept sqe. Let's integrate it to fast poll, it may
>> be good for other operations in the future.
>>
>> Signed-off-by: Hao Xu <[email protected]>
>> ---
>> fs/io_uring.c | 41 ++++++++++++++++++++++++++---------------
>> 1 file changed, 26 insertions(+), 15 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 8ebb1a794e36..d33777575faf 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -5952,7 +5952,7 @@ static void io_poll_remove_entries(struct io_kiocb *req)
>> * either spurious wakeup or multishot CQE is served. 0 when it's done with
>> * the request, then the mask is stored in req->cqe.res.
>> */
>> -static int io_poll_check_events(struct io_kiocb *req, bool locked)
>> +static int io_poll_check_events(struct io_kiocb *req, bool *locked)
>> {
>> struct io_ring_ctx *ctx = req->ctx;
>> int v;
>> @@ -5981,17 +5981,26 @@ static int io_poll_check_events(struct io_kiocb *req, bool locked)
>> /* multishot, just fill an CQE and proceed */
>> if (req->cqe.res && !(req->apoll_events & EPOLLONESHOT)) {
>> - __poll_t mask = mangle_poll(req->cqe.res & req->apoll_events);
>> - bool filled;
>> -
>> - spin_lock(&ctx->completion_lock);
>> - filled = io_fill_cqe_aux(ctx, req->cqe.user_data, mask,
>> - IORING_CQE_F_MORE);
>> - io_commit_cqring(ctx);
>> - spin_unlock(&ctx->completion_lock);
>> - if (unlikely(!filled))
>> - return -ECANCELED;
>> - io_cqring_ev_posted(ctx);
>> + if (req->flags & REQ_F_APOLL_MULTISHOT) {
>> + io_tw_lock(req->ctx, locked);
>> + if (likely(!(req->task->flags & PF_EXITING)))
>> + io_queue_sqe(req);
>
> That looks dangerous, io_queue_sqe() usually takes the request
> ownership and doesn't expect that someone, i.e.
> io_poll_check_events(), may still be actively using it.
I took a look at this, too. We do own the request at this point, but
it's still on the poll list. If io_accept() fails, then we do run the
poll_clean.
> E.g. io_accept() fails on fd < 0, return an error, io_queue_sqe() ->
> io_queue_async() -> io_req_complete_failed() kills it. Then
> io_poll_check_events() and polling in general carry on using the freed
> request => UAF. Didn't look at it too carefully, but there might other
> similar cases.
But we better have done poll_clean() before returning the error. What am
I missing here?
--
Jens Axboe
next prev parent reply other threads:[~2022-05-06 22:02 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-06 7:00 [PATCH v2 0/5] fast poll multishot mode Hao Xu
2022-05-06 7:00 ` [PATCH 1/5] io_uring: add IORING_ACCEPT_MULTISHOT for accept Hao Xu
2022-05-06 14:32 ` Jens Axboe
2022-05-07 4:05 ` Hao Xu
2022-05-06 7:00 ` [PATCH 2/5] io_uring: add REQ_F_APOLL_MULTISHOT for requests Hao Xu
2022-05-06 7:01 ` [PATCH 3/5] io_uring: let fast poll support multishot Hao Xu
2022-05-06 17:19 ` Pavel Begunkov
2022-05-06 22:02 ` Jens Axboe [this message]
2022-05-07 6:32 ` Hao Xu
2022-05-07 9:26 ` Pavel Begunkov
2022-05-07 7:08 ` Hao Xu
2022-05-07 9:47 ` Pavel Begunkov
2022-05-07 11:06 ` Hao Xu
2022-05-06 18:02 ` kernel test robot
2022-05-06 7:01 ` [PATCH 4/5] io_uring: add a helper for poll clean Hao Xu
2022-05-06 11:04 ` kernel test robot
2022-05-06 12:47 ` kernel test robot
2022-05-06 14:36 ` Jens Axboe
2022-05-07 6:37 ` Hao Xu
2022-05-06 16:22 ` Pavel Begunkov
2022-05-07 6:43 ` Hao Xu
2022-05-07 9:29 ` Pavel Begunkov
2022-05-06 7:01 ` [PATCH 5/5] io_uring: implement multishot mode for accept Hao Xu
2022-05-06 14:42 ` Jens Axboe
2022-05-07 9:13 ` Hao Xu
2022-05-06 20:50 ` Jens Axboe
2022-05-06 21:29 ` Jens Axboe
2022-05-06 7:36 ` [PATCH v2 0/5] fast poll multishot mode Hao Xu
2022-05-06 14:18 ` Jens Axboe
2022-05-06 16:01 ` Pavel Begunkov
2022-05-06 16:03 ` Jens Axboe
2022-05-06 22:23 ` Jens Axboe
2022-05-06 23:26 ` Jens Axboe
2022-05-07 2:33 ` Jens Axboe
2022-05-07 3:08 ` Jens Axboe
2022-05-07 16:01 ` Hao Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox