From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amit Pundir Date: Tue, 09 May 2017 14:54:38 +0000 Subject: [PATCH for-3.18 14/24] ppp: defer netns reference release for ppp channel Message-Id: <1494340968-17152-15-git-send-email-amit.pundir@linaro.org> List-Id: References: <1494340968-17152-1-git-send-email-amit.pundir@linaro.org> In-Reply-To: <1494340968-17152-1-git-send-email-amit.pundir@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Greg KH Cc: stable@vger.kernel.org, WANG Cong , Paul Mackerras , linux-ppp@vger.kernel.org, Guillaume Nault , Cyrill Gorcunov , "David S . Miller" From: WANG Cong commit 205e1e255c479f3fd77446415706463b282f94e4 upstream. Matt reported that we have a NULL pointer dereference in ppp_pernet() from ppp_connect_channel(), i.e. pch->chan_net is NULL. This is due to that a parallel ppp_unregister_channel() could happen while we are in ppp_connect_channel(), during which pch->chan_net set to NULL. Since we need a reference to net per channel, it makes sense to sync the refcnt with the life time of the channel, therefore we should release this reference when we destroy it. Fixes: 1f461dcdd296 ("ppp: take reference on channels netns") Reported-by: Matt Bennett Cc: Paul Mackerras Cc: linux-ppp@vger.kernel.org Cc: Guillaume Nault Cc: Cyrill Gorcunov Signed-off-by: Cong Wang Reviewed-by: Cyrill Gorcunov Signed-off-by: David S. Miller Signed-off-by: Amit Pundir --- drivers/net/ppp/ppp_generic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index e3fbbbbd84e7..3dd1c19756ec 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -2342,8 +2342,6 @@ ppp_unregister_channel(struct ppp_channel *chan) spin_lock_bh(&pn->all_channels_lock); list_del(&pch->list); spin_unlock_bh(&pn->all_channels_lock); - put_net(pch->chan_net); - pch->chan_net = NULL; pch->file.dead = 1; wake_up_interruptible(&pch->file.rwait); @@ -2960,6 +2958,9 @@ ppp_disconnect_channel(struct channel *pch) */ static void ppp_destroy_channel(struct channel *pch) { + put_net(pch->chan_net); + pch->chan_net = NULL; + atomic_dec(&channel_count); if (!pch->file.dead) { -- 2.7.4