From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932595AbcBJFGj (ORCPT ); Wed, 10 Feb 2016 00:06:39 -0500 Received: from mail-ob0-f169.google.com ([209.85.214.169]:36307 "EHLO mail-ob0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751250AbcBJFFm (ORCPT ); Wed, 10 Feb 2016 00:05:42 -0500 From: John Stultz To: lkml Cc: Riley Andrews , Colin Cross , =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Dmitry Shmidt , Rom Lemarchand , Serban Constantinescu , Greg Kroah-Hartman , Android Kernel Team , John Stultz Subject: [PATCH 2/2] android: drivers: Avoid debugfs race in binder Date: Tue, 9 Feb 2016 21:05:33 -0800 Message-Id: <1455080733-30965-3-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1455080733-30965-1-git-send-email-john.stultz@linaro.org> References: <1455080733-30965-1-git-send-email-john.stultz@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Riley Andrews If a /d/binder/proc/[pid] entry is kept open after linux has torn down the associated process, binder_proc_show can deference an invalid binder_proc that has been stashed in the debugfs inode. Validate that the binder_proc ptr passed into binder_proc_show has not been freed by looking for it within the global process list whilst the global lock is held. If the ptr is not valid, print nothing. Cc: Colin Cross Cc: Arve Hjønnevåg Cc: Dmitry Shmidt Cc: Rom Lemarchand Cc: Serban Constantinescu Cc: Greg Kroah-Hartman Cc: Android Kernel Team Signed-off-by: Dmitry Shmidt [jstultz: Minor commit message tweaks] Signed-off-by: John Stultz --- drivers/android/binder.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 1db3761..f0ce995 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -3600,13 +3600,24 @@ static int binder_transactions_show(struct seq_file *m, void *unused) static int binder_proc_show(struct seq_file *m, void *unused) { + struct binder_proc *itr; struct binder_proc *proc = m->private; int do_lock = !binder_debug_no_lock; + bool valid_proc = false; if (do_lock) binder_lock(__func__); - seq_puts(m, "binder proc state:\n"); - print_binder_proc(m, proc, 1); + + hlist_for_each_entry(itr, &binder_procs, proc_node) { + if (itr == proc) { + valid_proc = true; + break; + } + } + if (valid_proc) { + seq_puts(m, "binder proc state:\n"); + print_binder_proc(m, proc, 1); + } if (do_lock) binder_unlock(__func__); return 0; -- 1.9.1