Re: [PATCH] io_uring: fix deferred req iovec leak

Pavel Begunkov
2020-02-06T17:17:17Z

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On 06/02/2020 20:04, Pavel Begunkov wrote:
> On 06/02/2020 19:51, Pavel Begunkov wrote:
>> After defer, a request will be prepared, that includes allocating iovec
>> if needed, and then submitted through io_wq_submit_work() but not custom
>> handler (e.g. io_rw_async()/io_sendrecv_async()). However, it'll leak
>> iovec, as it's in io-wq and the code goes as follows:
>>
>> io_read() {
>> if (!io_wq_current_is_worker())
>> kfree(iovec);
>> }
>>
>> Put all deallocation logic in io_{read,write,send,recv}(), which will
>> leave the memory, if going async with -EAGAIN.
>>
> Interestingly, this will fail badly if it returns -EAGAIN from io-wq context.
> Apparently, I need to do v2.
>
Or not...
Jens, can you please explain what's with the -EAGAIN handling in
io_wq_submit_work()? Checking the code, it seems neither of
read/write/recv/send can return -EAGAIN from async context (i.e.
force_nonblock=false). Are there other ops that can do it?

>> It also fixes a leak after failed io_alloc_async_ctx() in
>> io_{recv,send}_msg().
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>> ---
>> fs/io_uring.c | 47 ++++++++++++-----------------------------------
>> 1 file changed, 12 insertions(+), 35 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index bff7a03e873f..ce3dbd2b1b5c 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -2143,17 +2143,6 @@ static int io_alloc_async_ctx(struct io_kiocb *req)
>> return req->io == NULL;
>> }
>>
>> -static void io_rw_async(struct io_wq_work **workptr)
>> -{
>> - struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
>> - struct iovec *iov = NULL;
>> -
>> - if (req->io->rw.iov != req->io->rw.fast_iov)
>> - iov = req->io->rw.iov;
>> - io_wq_submit_work(workptr);
>> - kfree(iov);
>> -}
>> -
>> static int io_setup_async_rw(struct io_kiocb *req, ssize_t io_size,
>> struct iovec *iovec, struct iovec *fast_iov,
>> struct iov_iter *iter)
>> @@ -2166,7 +2155,6 @@ static int io_setup_async_rw(struct io_kiocb *req, ssize_t io_size,
>>
>> io_req_map_rw(req, io_size, iovec, fast_iov, iter);
>> }
>> - req->work.func = io_rw_async;
>> return 0;
>> }
>>
>> @@ -2253,8 +2241,7 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
>> }
>> }
>> out_free:
>> - if (!io_wq_current_is_worker())
>> - kfree(iovec);
>> + kfree(iovec);
>> return ret;
>> }
>>
>> @@ -2359,8 +2346,7 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
>> }
>> }
>> out_free:
>> - if (!io_wq_current_is_worker())
>> - kfree(iovec);
>> + kfree(iovec);
>> return ret;
>> }
>>
>> @@ -2955,19 +2941,6 @@ static int io_sync_file_range(struct io_kiocb *req, struct io_kiocb **nxt,
>> return 0;
>> }
>>
>> -#if defined(CONFIG_NET)
>> -static void io_sendrecv_async(struct io_wq_work **workptr)
>> -{
>> - struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
>> - struct iovec *iov = NULL;
>> -
>> - if (req->io->rw.iov != req->io->rw.fast_iov)
>> - iov = req->io->msg.iov;
>> - io_wq_submit_work(workptr);
>> - kfree(iov);
>> -}
>> -#endif
>> -
>> static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>> {
>> #if defined(CONFIG_NET)
>> @@ -3036,17 +3009,19 @@ static int io_sendmsg(struct io_kiocb *req, struct io_kiocb **nxt,
>> if (force_nonblock && ret == -EAGAIN) {
>> if (req->io)
>> return -EAGAIN;
>> - if (io_alloc_async_ctx(req))
>> + if (io_alloc_async_ctx(req)) {
>> + if (kmsg && kmsg->iov != kmsg->fast_iov)
>> + kfree(kmsg->iov);
>> return -ENOMEM;
>> + }
>> memcpy(&req->io->msg, &io.msg, sizeof(io.msg));
>> - req->work.func = io_sendrecv_async;
>> return -EAGAIN;
>> }
>> if (ret == -ERESTARTSYS)
>> ret = -EINTR;
>> }
>>
>> - if (!io_wq_current_is_worker() && kmsg && kmsg->iov != kmsg->fast_iov)
>> + if (kmsg && kmsg->iov != kmsg->fast_iov)
>> kfree(kmsg->iov);
>> io_cqring_add_event(req, ret);
>> if (ret < 0)
>> @@ -3180,17 +3155,19 @@ static int io_recvmsg(struct io_kiocb *req, struct io_kiocb **nxt,
>> if (force_nonblock && ret == -EAGAIN) {
>> if (req->io)
>> return -EAGAIN;
>> - if (io_alloc_async_ctx(req))
>> + if (io_alloc_async_ctx(req)) {
>> + if (kmsg && kmsg->iov != kmsg->fast_iov)
>> + kfree(kmsg->iov);
>> return -ENOMEM;
>> + }
>> memcpy(&req->io->msg, &io.msg, sizeof(io.msg));
>> - req->work.func = io_sendrecv_async;
>> return -EAGAIN;
>> }
>> if (ret == -ERESTARTSYS)
>> ret = -EINTR;
>> }
>>
>> - if (!io_wq_current_is_worker() && kmsg && kmsg->iov != kmsg->fast_iov)
>> + if (kmsg && kmsg->iov != kmsg->fast_iov)
>> kfree(kmsg->iov);
>> io_cqring_add_event(req, ret);
>> if (ret < 0)