From patchwork Fri Feb 5 02:23:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Kalesh Singh X-Patchwork-Id: 377306 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham 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 6DA6FC4332B for ; Fri, 5 Feb 2021 02:24:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12C6464FB9 for ; Fri, 5 Feb 2021 02:24:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229979AbhBECYW (ORCPT ); Thu, 4 Feb 2021 21:24:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229972AbhBECYS (ORCPT ); Thu, 4 Feb 2021 21:24:18 -0500 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0D8CC06178C for ; Thu, 4 Feb 2021 18:23:37 -0800 (PST) Received: by mail-qv1-xf49.google.com with SMTP id e10so3752097qvp.22 for ; Thu, 04 Feb 2021 18:23:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:cc :content-transfer-encoding; bh=w382r+buQ4Tx8FdN/ryZgjV6D4PrxeZkE7hCNPLCCTk=; b=NPnaeEsHxHi/piRE30L1x8OZG9uQMUa5w0+x+UsNeCLDh53QMbkeU5Lgv6AyU09LNL DvZlEMtUnBsxCDBL3yrqJy92tZ8kFjhjM6bzzE7sIcdxQ7PurT0Y5gjLSEt88GT81AYX WXWOItSdEv/zp5NuWxav6asdBkP2pAw/kOD1AnK0PBVvEtmZ5Vwefg6MQI3tsn4OPMdQ plwXe0QwouLzjvGwfsA8yTvslcXQXLi9bh5ko/UbSEtwbYpopaH0W1YUG2ZFACQHPL7l aActAi6eUrI0CpI9j3fYhDfEmO/xw1jFkDq687flA8YUAwa0Ql6pjLhJOgq6C4n0nFdi HETw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :cc:content-transfer-encoding; bh=w382r+buQ4Tx8FdN/ryZgjV6D4PrxeZkE7hCNPLCCTk=; b=tghcEXG+geRsGyofonQtNb7HcQQOrVL+vJszMByeX/7gHEjE1OixRczV8dPvNoqpex ftFCeYbPrFBc/VC0E5lLAyWCuD1/krWUK/Q8wQrpvNWEVj0x7MDKGxWDoM4DkbVgAdP9 aUvgm/H8GMLFG37PNXyXMfgCfW8kI1yye0AA7E6DqHfYU/aRQNjIwbKT1zCk50P7DjWv F+LB3LxfubX7KEXVyHaSYpKJ6bubV92jCMLG67Iw14omcbmH3fDhqYjzznJFHuOFrlIP ndIbkaKYJZAcDjqg8qEcRCZ5rgH1gh5eAmaIp2a9nDV3yduX9D3wikr0npMfBbki5AT4 wIKQ== X-Gm-Message-State: AOAM531V9yNSS1EMVaM6IpWgGSvp0Y6osS2PwR8nKrA2Sh0GlisgkbZt r/83BHlqOpW4lMG23tXUvHhAyqmr6vyTgq+wzg== X-Google-Smtp-Source: ABdhPJyxJEHoxHNUAnY+G03oBvTfa0zSu7hUtgPrQ8bfbdtGtODePabYUrPF86ehavcU7ZNb7W60emHq1FCLFEcRNw== Sender: "kaleshsingh via sendgmr" X-Received: from kaleshsingh.c.googlers.com ([fda3:e722:ac3:cc00:14:4d90:c0a8:2145]) (user=kaleshsingh job=sendgmr) by 2002:a05:6214:446:: with SMTP id cc6mr2447707qvb.31.1612491816769; Thu, 04 Feb 2021 18:23:36 -0800 (PST) Date: Fri, 5 Feb 2021 02:23:19 +0000 Message-Id: <20210205022328.481524-1-kaleshsingh@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.30.0.365.g02bc693789-goog Subject: [PATCH v3 1/2] procfs: Allow reading fdinfo with PTRACE_MODE_READ From: Kalesh Singh Cc: jannh@google.com, jeffv@google.com, keescook@chromium.org, surenb@google.com, minchan@kernel.org, hridya@google.com, kernel-team@android.com, Kalesh Singh , Alexey Dobriyan , Jonathan Corbet , Sumit Semwal , "=?UTF-8?q?Christian=20K=C3=B6nig?=" , Andrew Morton , Mauro Carvalho Chehab , Michal Hocko , Alexey Gladkov , Randy Dunlap , Anand K Mistry , "Eric W. Biederman" , Michel Lespinasse , Bernd Edlinger , Andrei Vagin , Yafang Shao , Christian Brauner , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Android captures per-process system memory state when certain low memory events (e.g a foreground app kill) occur, to identify potential memory hoggers. In order to measure how much memory a process actually consumes, it is necessary to include the DMA buffer sizes for that process in the memory accounting. Since the handle to DMA buffers are raw FDs, it is important to be able to identify which processes have FD references to a DMA buffer. Currently, DMA buffer FDs can be accounted using /proc//fd/* and /proc//fdinfo -- both are only readable by the process owner, as follows: 1. Do a readlink on each FD. 2. If the target path begins with "/dmabuf", then the FD is a dmabuf FD. 3. stat the file to get the dmabuf inode number. 4. Read/ proc//fdinfo/, to get the DMA buffer size. Accessing other processes’ fdinfo requires root privileges. This limits the use of the interface to debugging environments and is not suitable for production builds. Granting root privileges even to a system process increases the attack surface and is highly undesirable. Since fdinfo doesn't permit reading process memory and manipulating process state, allow accessing fdinfo under PTRACE_MODE_READ_FSCRED. Suggested-by: Jann Horn Signed-off-by: Kalesh Singh Acked-by: Randy Dunlap # for Documentation/filesystems/proc.rst --- Changes in v2: - Update patch description fs/proc/base.c | 4 ++-- fs/proc/fd.c | 15 ++++++++++++++- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index b3422cda2a91..a37f9de7103f 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3160,7 +3160,7 @@ static const struct pid_entry tgid_base_stuff[] = { DIR("task", S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations), DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations), DIR("map_files", S_IRUSR|S_IXUSR, proc_map_files_inode_operations, proc_map_files_operations), - DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations), + DIR("fdinfo", S_IRUGO|S_IXUGO, proc_fdinfo_inode_operations, proc_fdinfo_operations), DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations), #ifdef CONFIG_NET DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations), @@ -3504,7 +3504,7 @@ static const struct inode_operations proc_tid_comm_inode_operations = { */ static const struct pid_entry tid_base_stuff[] = { DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations), - DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations), + DIR("fdinfo", S_IRUGO|S_IXUGO, proc_fdinfo_inode_operations, proc_fdinfo_operations), DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations), #ifdef CONFIG_NET DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations), diff --git a/fs/proc/fd.c b/fs/proc/fd.c index cb51763ed554..585e213301f9 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -6,6 +6,7 @@ #include #include #include +#include #include #include #include @@ -72,6 +73,18 @@ static int seq_show(struct seq_file *m, void *v) static int seq_fdinfo_open(struct inode *inode, struct file *file) { + bool allowed = false; + struct task_struct *task = get_proc_task(inode); + + if (!task) + return -ESRCH; + + allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); + put_task_struct(task); + + if (!allowed) + return -EACCES; + return single_open(file, seq_show, inode); } @@ -307,7 +320,7 @@ static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry, struct proc_inode *ei; struct inode *inode; - inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUSR); + inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO); if (!inode) return ERR_PTR(-ENOENT);