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=-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 DF75DC433E0 for ; Thu, 4 Feb 2021 23:31:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A30664E0F for ; Thu, 4 Feb 2021 23:31:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230264AbhBDXbC (ORCPT ); Thu, 4 Feb 2021 18:31:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230221AbhBDXaj (ORCPT ); Thu, 4 Feb 2021 18:30:39 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 772D6C061794 for ; Thu, 4 Feb 2021 15:29:59 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id n81so4856764ybg.20 for ; Thu, 04 Feb 2021 15:29:59 -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=DDQzxO36o6mrG/7K72IGYqFtZmZCZagcSZoIJct7BXY=; b=lKA+G8wZwzc3KJjfEbk4USd/5AVvIdDVeMqb73oE9zBHWMZoft6gFKDOCePms0HPGp IpnAmcQPaJqYzhqs4VxxZC2o6/RZ/j5MJHU506eq+wz0Kr/o5Bqyr8NtakeP4tNzVayK i4uqXx2mJwpp7gFTlPgCqkmcAAnU1hJ5Od8hNOtrD2rvM4Bv5eQodRsQ3Nbv41EYSlj6 QIkP+5XgiBOggGll6NMhjXYbeQvpSVtgbaWyekgEHyE8uT0kDLBHzAO8Q2g0J/qrcZqc 4I6ra63n/sjej0sFgwE/GkqMywm97NzAFEwHafPA+4J8xTPVBMHAUXrR3IlMDzqYSjeR 6m0w== 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=DDQzxO36o6mrG/7K72IGYqFtZmZCZagcSZoIJct7BXY=; b=DOKQybd6SSRR3nfk4DJfiW0WDuwoHi/T4CLx/nFcqAzDIGcQBBLolA7ZFlk7IRvHoF ysZ9RcOFGAOQ83PtFC6UvvA3r7e2kcF3ccjIcLNM0uVbRo8e2DiChwtC4pH0S64NaTEZ 7xwSF6JvuWxPCf2Ysez6+Gl7D58VV3/Bm+72A+A1TeS4537KoPBuzvgTi88OQKIJEL1N agkV7PKy2pFRjt163+oFfdPmUJ9nEVjAgmnmbCCK7qowi8+sibWWC6c/LBEK0Yt/0XIN rxRFGxKkXzvGhdZcn8S+TrgIA0ABRAAD0nxO46Ggm3iES9kkT2sMIFqMy2091YMNb30P 9VJA== X-Gm-Message-State: AOAM533eew/BBEWa5mqwaPt6J8bWeoP44wzmt9ZRCPrGKX/0Q5WN3lo5 Q6nCocQlRCO+DM4jAF02mKfEvB1rRZh61lGS6w== X-Google-Smtp-Source: ABdhPJxuX5H3dPiFCh9g9xC89BwbDPdhdkk9a69MMrBZXYzdZFIf3f0iRjx/t1FkfEnOk7GPoDaKkXJi/cFoZs5jWQ== 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:a25:450:: with SMTP id 77mr162814ybe.39.1612481398666; Thu, 04 Feb 2021 15:29:58 -0800 (PST) Date: Thu, 4 Feb 2021 23:28:49 +0000 Message-Id: <20210204232854.451676-1-kaleshsingh@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.30.0.365.g02bc693789-goog Subject: [PATCH v2 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 , Sumit Semwal , "=?UTF-8?q?Christian=20K=C3=B6nig?=" , Alexey Dobriyan , "Eric W. Biederman" , Andrew Morton , Alexey Gladkov , Vlastimil Babka , Michel Lespinasse , Bernd Edlinger , Andrei Vagin , Yafang Shao , Christian Brauner , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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=E2=80=99 fdinfo requires root privileges. This li= mits 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 desciption 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[] =3D { 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_oper= ations), 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_fdi= nfo_operations), + DIR("fdinfo", S_IRUGO|S_IXUGO, proc_fdinfo_inode_operations, proc_fdi= nfo_operations), DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_op= erations), #ifdef CONFIG_NET DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_op= erations), @@ -3504,7 +3504,7 @@ static const struct inode_operations proc_tid_comm_in= ode_operations =3D { */ static const struct pid_entry tid_base_stuff[] =3D { DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_opera= tions), - DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdin= fo_operations), + DIR("fdinfo", S_IRUGO|S_IXUGO, proc_fdinfo_inode_operations, proc_fdin= fo_operations), DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_ope= rations), #ifdef CONFIG_NET DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_op= erations), 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) =20 static int seq_fdinfo_open(struct inode *inode, struct file *file) { + bool allowed =3D false; + struct task_struct *task =3D get_proc_task(inode); + + if (!task) + return -ESRCH; + + allowed =3D ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); + put_task_struct(task); + + if (!allowed) + return -EACCES; + return single_open(file, seq_show, inode); } =20 @@ -307,7 +320,7 @@ static struct dentry *proc_fdinfo_instantiate(struct de= ntry *dentry, struct proc_inode *ei; struct inode *inode; =20 - inode =3D proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUSR); + inode =3D proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO); if (!inode) return ERR_PTR(-ENOENT); =20 --=20 2.30.0.365.g02bc693789-goog