From patchwork Mon Feb 8 15:53:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kalesh Singh X-Patchwork-Id: 12075943 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 A4F00C433E6 for ; Mon, 8 Feb 2021 15:54:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D50F64E50 for ; Mon, 8 Feb 2021 15:54:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234216AbhBHPyU (ORCPT ); Mon, 8 Feb 2021 10:54:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234210AbhBHPx7 (ORCPT ); Mon, 8 Feb 2021 10:53:59 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53450C06178A for ; Mon, 8 Feb 2021 07:53:19 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id 11so17430925ybl.21 for ; Mon, 08 Feb 2021 07:53:19 -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=KABW1PbKP87UHlmwOVcrjPZPD/KiH4IFW6HwyHI8HLw=; b=k+plAvQWKUQQEFSYtdDrmR64LjfOFfyNvE5bQyLeuXXk0gQM9M1YLhI+Kpb8Pq6RRy xXUgZ8Lu748qxXqRshn9BfzpFkBuZqYWwc0HB+CQPVijF0hLdpKZa0Wx4BE7Cq3qKTcG 4YemrGBQUUzxrqVLCDIK+5YyUj35ExFZfnKSA5iVF/fkayXaj4lu7prTK/0JiyDIhICI fXnLZV8WgGU72cjZral6rTKmmKeGcLVviG4fVVZG1/XbYWgaMoD+guk+XrCXEOwOG7++ Q2YwHsK7pUuG96I5oZHtxrbJLTTP4zgpIcc4M/9Rss6yk5IY9M17KM/eqzugs31WXzmT 5VjA== 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=KABW1PbKP87UHlmwOVcrjPZPD/KiH4IFW6HwyHI8HLw=; b=JHKK/k8eunob3lwRt7jUC/XopLkMe1lPK/NH2SEAg7yutun4nyg9h+UnMYSTGvOD/3 Ya1Et1miLPrlOKOENGMrwzOMoLSCcE0w2hf/RGYSvVEFEzR5dIDDQRuJmFEwchgDrzJw s+iKGMGZGJWp3jlcUyhEwfWlKucXrGQNzJBYccnu6eeEvIdX6mR5HbCrIXw5EpSS4ivl 5MH8fkQ0/6Ei87SdYaPJOvyk/eCylO41HNB7/0N16V70TTqlYNJhWm4QMnGT6sJ3MSqm Pi6pqTrihzEtE0uKyTZG6x8kiC0p32lUE0HLixwPD+z+WnPOqOvz7V0adzjZrw0Iws/J I7kg== X-Gm-Message-State: AOAM5324Wly4SYlSXSIhbqLM4etfGHqmfvgEIIMlzmPze9VVFa0Jp5Au OEOqauFHAePfszQKqxEexf11KmyuyREmgzxUTA== X-Google-Smtp-Source: ABdhPJy5TCKk45UVECdZNGWDZgT1hEcr/O9DAIgFSw2AggyhYlchwyA7OBiwJdM5EuiQp2ZNxIUAKTng2zlyA28byw== 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:a25:a267:: with SMTP id b94mr25868498ybi.218.1612799598492; Mon, 08 Feb 2021 07:53:18 -0800 (PST) Date: Mon, 8 Feb 2021 15:53:06 +0000 Message-Id: <20210208155315.1367371-1-kaleshsingh@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.30.0.478.g8a0d178c01-goog Subject: [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, kernel-team@android.com, Kalesh Singh , Alexey Dobriyan , Jonathan Corbet , Mauro Carvalho Chehab , Andrew Morton , Michal Hocko , Alexey Gladkov , NeilBrown , "Eric W. Biederman" , Daniel Jordan , 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 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 --- 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);