From patchwork Mon Mar 8 17:06:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kalesh Singh X-Patchwork-Id: 12122979 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=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 E8BC7C433E9 for ; Mon, 8 Mar 2021 17:08:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF32B65230 for ; Mon, 8 Mar 2021 17:08:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230475AbhCHRHt (ORCPT ); Mon, 8 Mar 2021 12:07:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34766 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230002AbhCHRHQ (ORCPT ); Mon, 8 Mar 2021 12:07:16 -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 52AC1C06175F for ; Mon, 8 Mar 2021 09:07:16 -0800 (PST) Received: by mail-qv1-xf49.google.com with SMTP id dz17so8128831qvb.14 for ; Mon, 08 Mar 2021 09:07:16 -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; bh=7mCRpmhv1OM36vNlkAtqHtWEhlUKPQI2C+wk9QTsT80=; b=miOOpv1RLxFINJF7EYHrzJzD3khYSf16V5pPLLmhxznHshwiurgylwUbtsXLx/GoPJ E4qC1svZwWEj/bXdNmvg5CGJzUHhR5Y9P9OWIatPV1Ja2AyN/hzWec0bxrfow92fYY3I EpUzhabEWV2Kblsu3IglcUnYAOLa0xlESIWPOBFI4z3hnpejjSlW5DbJGEI7VwZB5XmI 5VcR6tW/GZjaU5fOBzMzt8dod0HiT/b0wdReP0Pq7fe19dWJm7pOfW5ZKGdY5EV9lGTm fi0JUcAaB3pzkbmBwgyZAkRBDTIsAFXVLxwO8LLHSY8lp0UhE7gIQP2x5JvqDYEj/6IS cJ/g== 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; bh=7mCRpmhv1OM36vNlkAtqHtWEhlUKPQI2C+wk9QTsT80=; b=s+LhJeCP5vEp4oivFTnlq53Q6ud4R4dXV+tbmXAW8hoMgS80FTzvX9+oAVYdKoPnd7 7mexqdqhCNB/c//Uv94iLPItcPRhWZjz0oaePzS/aZsalLa+KiA0QtLauUFNxhLHa2WQ zn8kRWGOURjRJq4IzvMSvGR23PU5mZ6yoZ/6pCqX+6DmFymuIvQqLFeaGIFcEa6nSbi6 cY/abut69sxSFFprLnXoU3XTm/y8k6eBuktH3qM2v5tnuPzfzBbypYU/cOQ1wnscjKmx qL4xJuULIIWq7q739QUogELkvx+Oujt/pE7iLD3+D3AEUKzaxprtlzBZfjnVXxa0vbvV d+QA== X-Gm-Message-State: AOAM5313jChFhRmrQLVpOYN51kpsT2EVdAW0rWmu/bNR5O27sotcCzy/ P2xHDF6UerjzUc6YHoTqiVkn/pnOZxilAiAkTw== X-Google-Smtp-Source: ABdhPJx9+q+MEXXOho3t/3yQ+LqETPemrMlYxWkhxLoiKwMhnO2xsjvoochQa6vlE3++weFzUkrdxqvsxq+Dbq6zpA== Sender: "kaleshsingh via sendgmr" X-Received: from kaleshsingh.c.googlers.com ([fda3:e722:ac3:10:14:4d90:c0a8:2145]) (user=kaleshsingh job=sendgmr) by 2002:a0c:b526:: with SMTP id d38mr21324197qve.7.1615223235257; Mon, 08 Mar 2021 09:07:15 -0800 (PST) Date: Mon, 8 Mar 2021 17:06:40 +0000 Message-Id: <20210308170651.919148-1-kaleshsingh@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.30.1.766.gb4fecdf3b7-goog Subject: [RESEND PATCH v6 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, rdunlap@infradead.org, christian.koenig@amd.com, willy@infradead.org, viro@zeniv.linux.org.uk, kernel-team@android.com, Kalesh Singh , Alexey Dobriyan , Jonathan Corbet , Andrew Morton , Mauro Carvalho Chehab , Michal Hocko , Alexey Gladkov , Szabolcs Nagy , "Eric W. Biederman" , Christian Brauner , Michel Lespinasse , Bernd Edlinger , Andrei Vagin , Helge Deller , James Morris , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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 Reviewed-by: Kees Cook --- Hi everyone, The initial posting of this patch can be found at [1]. I didn't receive any feedback last time, so resending here. Would really appreciate any constructive comments/suggestions. Thanks, Kalesh [1] https://lore.kernel.org/r/20210208155315.1367371-1-kaleshsingh@google.com/ 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 3851bfcdba56..fd46d8dd0cf4 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3159,7 +3159,7 @@ 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 07fc4fad2602..6a80b40fd2fe 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); } @@ -308,7 +321,7 @@ 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);