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

Pavel Begunkov
2020-02-06T17:05:21Z

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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.

> 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)