From nobody Mon Sep 29 20:17:15 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53A4DC28B2C for ; Mon, 15 Aug 2022 22:03:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347038AbiHOWDE (ORCPT ); Mon, 15 Aug 2022 18:03:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347537AbiHOWAo (ORCPT ); Mon, 15 Aug 2022 18:00:44 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53877167F1; Mon, 15 Aug 2022 12:35:26 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E0DFE611E4; Mon, 15 Aug 2022 19:35:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBBD4C433D6; Mon, 15 Aug 2022 19:35:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660592109; bh=Wujj5i866p9om6sVU/5OKGHjwQgKQ35nherAfS8OOgs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Luna2qnUDcZ9YV/yIKjYA52ygw9clZOCo5BtYeUFaDGWmb22xTA+k5RZjaEFq4Z/9 POWslPxCmngccm4O1SpwB8Y4Cq/2MrSeVN5id85rVTfwxkgvFSPPCWHwbqKYj1XZ/X eTKeC9o6ky3bNCzTP6CxyisIzTCnyyi8ggOzYOQQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jeff Layton , "Christian Brauner (Microsoft)" , Al Viro , stable@kernel.org Subject: [PATCH 5.19 0060/1157] fix short copy handling in copy_mc_pipe_to_iter() Date: Mon, 15 Aug 2022 19:50:16 +0200 Message-Id: <20220815180441.901113302@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220815180439.416659447@linuxfoundation.org> References: <20220815180439.416659447@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Al Viro commit c3497fd009ef2c59eea60d21c3ac22de3585ed7d upstream. Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can result in a short copy. In that case we need to trim the unused buffers, as well as the length of partially filled one - it's not enough to set ->head, ->iov_offset and ->count to reflect how much had we copied. Not hard to fix, fortunately... I'd put a helper (pipe_discard_from(pipe, head)) into pipe_fs_i.h, rather than iov_iter.c - it has nothing to do with iov_iter and having it will allow us to avoid an ugly kludge in fs/splice.c. We could put it into lib/iov_iter.c for now and move it later, but I don't see the point going that way... Cc: stable@kernel.org # 4.19+ Fixes: ca146f6f091e "lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsaf= e()" Reviewed-by: Jeff Layton Reviewed-by: Christian Brauner (Microsoft) Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- include/linux/pipe_fs_i.h | 9 +++++++++ lib/iov_iter.c | 15 +++++++++++---- 2 files changed, 20 insertions(+), 4 deletions(-) --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -229,6 +229,15 @@ static inline bool pipe_buf_try_steal(st return buf->ops->try_steal(pipe, buf); } =20 +static inline void pipe_discard_from(struct pipe_inode_info *pipe, + unsigned int old_head) +{ + unsigned int mask =3D pipe->ring_size - 1; + + while (pipe->head > old_head) + pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]); +} + /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual memory allocation, whereas PIPE_BUF makes atomicity guarantees. */ #define PIPE_SIZE PAGE_SIZE --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -689,6 +689,7 @@ static size_t copy_mc_pipe_to_iter(const struct pipe_inode_info *pipe =3D i->pipe; unsigned int p_mask =3D pipe->ring_size - 1; unsigned int i_head; + unsigned int valid =3D pipe->head; size_t n, off, xfer =3D 0; =20 if (!sanity(i)) @@ -702,11 +703,17 @@ static size_t copy_mc_pipe_to_iter(const rem =3D copy_mc_to_kernel(p + off, addr + xfer, chunk); chunk -=3D rem; kunmap_local(p); - i->head =3D i_head; - i->iov_offset =3D off + chunk; - xfer +=3D chunk; - if (rem) + if (chunk) { + i->head =3D i_head; + i->iov_offset =3D off + chunk; + xfer +=3D chunk; + valid =3D i_head + 1; + } + if (rem) { + pipe->bufs[i_head & p_mask].len -=3D rem; + pipe_discard_from(pipe, valid); break; + } n -=3D chunk; off =3D 0; i_head++;