From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6EF02C282C2 for ; Wed, 23 Jan 2019 14:19:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 320D620870 for ; Wed, 23 Jan 2019 14:19:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lu+BVVEY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726872AbfAWOT0 (ORCPT ); Wed, 23 Jan 2019 09:19:26 -0500 Received: from mail-yw1-f74.google.com ([209.85.161.74]:45237 "EHLO mail-yw1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726200AbfAWOTZ (ORCPT ); Wed, 23 Jan 2019 09:19:25 -0500 Received: by mail-yw1-f74.google.com with SMTP id k69so1173407ywa.12 for ; Wed, 23 Jan 2019 06:19:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=YdTZcj4awLkuiDDlEY8FD2E/jDvXKOg3LBytxcu7mVU=; b=lu+BVVEYMxAL/KrTfwYAlxgvot43Q/Mns6Yeh7/yIyOJV29nPKkT9lUxroKxb1UTol x9WSGCNTyweuQ4Hv7kKPhavqo3M7SpYnWEQ0s8ku/f0CqSEnBbHwYRgaVRV0bqutWRSZ EXrhfRZFq4j8oePmj/cTz1Ji8I+p+TjhJcb2hdlEB5PrA9mM2+Rbev3Q+Y3LUkDrwkz7 bIWaMraK7RIayMEV4HxHAU0EJlK3mh+/KfeeF9jBtoqcGBZQr/Goc6Nd7KYVB+wUk8HI iFFmaDZS2ne8zreF9mb5yh00ekU7dqZwcXid8gI60csUYzoo3zuXVpq6hiXtI6BRLclb H6+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=YdTZcj4awLkuiDDlEY8FD2E/jDvXKOg3LBytxcu7mVU=; b=ZXZRpEY3lqFMpnVcwqHrhT3TRC/G1fpk0uD1E7PrxDiQd11hck4adDnLh1ySmSZReS xDlrbakXb3VAu4+iUd15DY4vpR4qOS8BP7jX6roMhYS2HlX6dpK0WIabmtT0Rj5o48mS oZYx29oxls5slBsaamM4phpy7CV3tImUPoakmlg3wB9kj0QFAEhqqzA0+qiShYUeJbKw fS1bG0APH9dCp86BRW5zY76r+tzyRzXTYlHxBTKvUdLBOajR4xcuGCd9dpNWptB+hlGK n8RjtVH6mG3V1jTCsqDqG/Fo1KQcHeNyZdg1RaOFOv2tdAej+ksznyyE1OY2HQ1LF1No V+rg== X-Gm-Message-State: AJcUukenKYTEQgZy5uDsokbIE6pIv4P3wdHgro11u4VJxV/t4c+MvLWR vuDZhjtfZzk4k1dH5v0nWDBSItrRzw== X-Google-Smtp-Source: ALg8bN7juJ6hMcbdu4GR7lWA1uM1JYyMs7fQif2GCpFQfVJXuVsShRI+e6riORdnPK9ZF0h4hlvldL61lA== X-Received: by 2002:a25:3b03:: with SMTP id i3mr686453yba.57.1548253163833; Wed, 23 Jan 2019 06:19:23 -0800 (PST) Date: Wed, 23 Jan 2019 15:19:17 +0100 Message-Id: <20190123141918.238286-1-jannh@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.20.1.321.g9e740568ce-goog Subject: [PATCH v2 1/2] splice: don't merge into linked buffers From: Jann Horn To: Al Viro , Miklos Szeredi , Jens Axboe , Jens Axboe , jannh@google.com Cc: Eric Biggers , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Kees Cook Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Before this patch, it was possible for two pipes to affect each other after data had been transferred between them with tee(): ============ $ cat tee_test.c int main(void) { int pipe_a[2]; if (pipe(pipe_a)) err(1, "pipe"); int pipe_b[2]; if (pipe(pipe_b)) err(1, "pipe"); if (write(pipe_a[1], "abcd", 4) != 4) err(1, "write"); if (tee(pipe_a[0], pipe_b[1], 2, 0) != 2) err(1, "tee"); if (write(pipe_b[1], "xx", 2) != 2) err(1, "write"); char buf[5]; if (read(pipe_a[0], buf, 4) != 4) err(1, "read"); buf[4] = 0; printf("got back: '%s'\n", buf); } $ gcc -o tee_test tee_test.c $ ./tee_test got back: 'abxx' $ ============ As suggested by Al Viro, fix it by creating a separate type for non-mergeable pipe buffers, then changing the types of buffers in splice_pipe_to_pipe() and link_pipe(). Cc: Fixes: 7c77f0b3f920 ("splice: implement pipe to pipe splicing") Fixes: 70524490ee2e ("[PATCH] splice: add support for sys_tee()") Suggested-by: Al Viro Signed-off-by: Jann Horn --- Al wasn't entirely happy with the approach I took for v1, so sending a different fix here. fs/pipe.c | 14 ++++++++++++++ fs/splice.c | 4 ++++ include/linux/pipe_fs_i.h | 1 + 3 files changed, 19 insertions(+) diff --git a/fs/pipe.c b/fs/pipe.c index bdc5d3c0977d..c51750ed4011 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -234,6 +234,14 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = { .get = generic_pipe_buf_get, }; +static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = { + .can_merge = 0, + .confirm = generic_pipe_buf_confirm, + .release = anon_pipe_buf_release, + .steal = anon_pipe_buf_steal, + .get = generic_pipe_buf_get, +}; + static const struct pipe_buf_operations packet_pipe_buf_ops = { .can_merge = 0, .confirm = generic_pipe_buf_confirm, @@ -242,6 +250,12 @@ static const struct pipe_buf_operations packet_pipe_buf_ops = { .get = generic_pipe_buf_get, }; +void pipe_buf_mark_unmergeable(struct pipe_buffer *buf) +{ + if (buf->ops == &anon_pipe_buf_ops) + buf->ops = &anon_pipe_buf_nomerge_ops; +} + static ssize_t pipe_read(struct kiocb *iocb, struct iov_iter *to) { diff --git a/fs/splice.c b/fs/splice.c index de2ede048473..90c29675d573 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1597,6 +1597,8 @@ static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, */ obuf->flags &= ~PIPE_BUF_FLAG_GIFT; + pipe_buf_mark_unmergeable(obuf); + obuf->len = len; opipe->nrbufs++; ibuf->offset += obuf->len; @@ -1671,6 +1673,8 @@ static int link_pipe(struct pipe_inode_info *ipipe, */ obuf->flags &= ~PIPE_BUF_FLAG_GIFT; + pipe_buf_mark_unmergeable(obuf); + if (obuf->len > len) obuf->len = len; diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 5a3bb3b7c9ad..3ecd7ea212ae 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -182,6 +182,7 @@ void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *); int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *); void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *); +void pipe_buf_mark_unmergeable(struct pipe_buffer *buf); extern const struct pipe_buf_operations nosteal_pipe_buf_ops; -- 2.20.1.321.g9e740568ce-goog