linux-kernel - Re: [PATCH] io_uring: fix deferred req iovec leak

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Message-ID: <d8486857-ccd3-41bd-2ef7-5ac4781dbd5f@gmail.com>
Date:   Thu, 6 Feb 2020 20:04:23 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring: fix deferred req iovec leak

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@...il.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)
> 

-- 
Pavel Begunkov



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