From: WANG Cong Date: Wed, 6 Jul 2016 05:12:36 +0000 (-0700) Subject: ppp: defer netns reference release for ppp channel X-Git-Tag: v3.16.39~297 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=554ab54b84651317f90c3b40a38365ae9ad671d8;p=thirdparty%2Fkernel%2Fstable.git ppp: defer netns reference release for ppp channel 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: Ben Hutchings --- diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 2b5ac1818797d..03054f55073ce 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -2338,8 +2338,6 @@ 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); @@ -2955,6 +2953,9 @@ 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) {