From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 073A32590 for ; Sun, 22 Jan 2023 15:14:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81F32C433EF; Sun, 22 Jan 2023 15:14:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1674400479; bh=N8UikIrmLV4NAq1qOTHsYsCi/692QTC3vJcLxeH6QVk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0Gt5ElRhmDZ7zLyQ/3WWkRS9WNEORNHiEdDUc1/P//FyJ24BbL1Q52bHVYI6BQIxq OmcWzKaqH8KBkVrU5TRGVxienUrv8Dsi+fU8jggpmwI1tELrQsAzlQPYvxArkK2XqU x7/nqoSeeqAsuJ6TjnpZ4Dv12wwPH6nsz73jNUjU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stefan Metzmacher , Pavel Begunkov , Jens Axboe Subject: [PATCH 5.10 91/98] io_uring/net: fix fast_iov assignment in io_setup_async_msg() Date: Sun, 22 Jan 2023 16:04:47 +0100 Message-Id: <20230122150233.265271095@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230122150229.351631432@linuxfoundation.org> References: <20230122150229.351631432@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Stefan Metzmacher commit 3e4cb6ebbb2bad201c1186bc0b7e8cf41dd7f7e6 upstream. I hit a very bad problem during my tests of SENDMSG_ZC. BUG(); in first_iovec_segment() triggered very easily. The problem was io_setup_async_msg() in the partial retry case, which seems to happen more often with _ZC. iov_iter_iovec_advance() may change i->iov in order to have i->iov_offset being only relative to the first element. Which means kmsg->msg.msg_iter.iov is no longer the same as kmsg->fast_iov. But this would rewind the copy to be the start of async_msg->fast_iov, which means the internal state of sync_msg->msg.msg_iter is inconsitent. I tested with 5 vectors with length like this 4, 0, 64, 20, 8388608 and got a short writes with: - ret=2675244 min_ret=8388692 => remaining 5713448 sr->done_io=2675244 - ret=-EAGAIN => io_uring_poll_arm - ret=4911225 min_ret=5713448 => remaining 802223 sr->done_io=7586469 - ret=-EAGAIN => io_uring_poll_arm - ret=802223 min_ret=802223 => res=8388692 While this was easily triggered with SENDMSG_ZC (queued for 6.1), it was a potential problem starting with 7ba89d2af17aa879dda30f5d5d3f152e587fc551 in 5.18 for IORING_OP_RECVMSG. And also with 4c3c09439c08b03d9503df0ca4c7619c5842892e in 5.19 for IORING_OP_SENDMSG. However 257e84a5377fbbc336ff563833a8712619acce56 introduced the critical code into io_setup_async_msg() in 5.11. Fixes: 7ba89d2af17aa ("io_uring: ensure recv and recvmsg handle MSG_WAITALL correctly") Fixes: 257e84a5377fb ("io_uring: refactor sendmsg/recvmsg iov managing") Cc: stable@vger.kernel.org Signed-off-by: Stefan Metzmacher Reviewed-by: Pavel Begunkov Link: https://lore.kernel.org/r/b2e7be246e2fb173520862b0c7098e55767567a2.1664436949.git.metze@samba.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- io_uring/io_uring.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -4681,8 +4681,10 @@ static int io_setup_async_msg(struct io_ if (async_msg->msg.msg_name) async_msg->msg.msg_name = &async_msg->addr; /* if were using fast_iov, set it to the new one */ - if (!async_msg->free_iov) - async_msg->msg.msg_iter.iov = async_msg->fast_iov; + if (!kmsg->free_iov) { + size_t fast_idx = kmsg->msg.msg_iter.iov - kmsg->fast_iov; + async_msg->msg.msg_iter.iov = &async_msg->fast_iov[fast_idx]; + } return -EAGAIN; }