Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755542AbaKYLf4 (ORCPT ); Tue, 25 Nov 2014 06:35:56 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:58462 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753256AbaKYKlg (ORCPT ); Tue, 25 Nov 2014 05:41:36 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Al Viro , Luis Henriques Subject: [PATCH 3.16.y-ckt 096/254] fix misuses of f_count() in ppp and netlink Date: Tue, 25 Nov 2014 10:37:26 +0000 Message-Id: <1416912004-5928-97-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1416912004-5928-1-git-send-email-luis.henriques@canonical.com> References: <1416912004-5928-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt2 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro commit 24dff96a37a2ca319e75a74d3929b2de22447ca6 upstream. we used to check for "nobody else could start doing anything with that opened file" by checking that refcount was 2 or less - one for descriptor table and one we'd acquired in fget() on the way to wherever we are. That was race-prone (somebody else might have had a reference to descriptor table and do fget() just as we'd been checking) and it had become flat-out incorrect back when we switched to fget_light() on those codepaths - unlike fget(), it doesn't grab an extra reference unless the descriptor table is shared. The same change allowed a race-free check, though - we are safe exactly when refcount is less than 2. It was a long time ago; pre-2.6.12 for ioctl() (the codepath leading to ppp one) and 2.6.17 for sendmsg() (netlink one). OTOH, netlink hadn't grown that check until 3.9 and ppp used to live in drivers/net, not drivers/net/ppp until 3.1. The bug existed well before that, though, and the same fix used to apply in old location of file. Signed-off-by: Al Viro Signed-off-by: Luis Henriques --- drivers/net/ppp/ppp_generic.c | 2 +- net/netlink/af_netlink.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index d5b77ef3a210..a75a411b1c27 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -594,7 +594,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg) if (file == ppp->owner) ppp_shutdown_interface(ppp); } - if (atomic_long_read(&file->f_count) <= 2) { + if (atomic_long_read(&file->f_count) < 2) { ppp_release(NULL, file); err = 0; } else diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 48fc607a211e..d158e1c888d8 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -707,7 +707,7 @@ static int netlink_mmap_sendmsg(struct sock *sk, struct msghdr *msg, * after validation, the socket and the ring may only be used by a * single process, otherwise we fall back to copying. */ - if (atomic_long_read(&sk->sk_socket->file->f_count) > 2 || + if (atomic_long_read(&sk->sk_socket->file->f_count) > 1 || atomic_read(&nlk->mapped) > 1) excl = false; -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/