| From | Ben Hutchings <> | Date | Mon, 14 Nov 2016 00:14:07 +0000 | Subject | [PATCH 3.2 014/152] ppp: defer netns reference release for ppp channel |
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3.2.84-rc1 review patch. If anyone has any objections, please let me know.
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From: WANG Cong <xiyou.wangcong@gmail.com>
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 <Matt.Bennett@alliedtelesis.co.nz> Cc: Paul Mackerras <paulus@samba.org> Cc: linux-ppp@vger.kernel.org Cc: Guillaume Nault <g.nault@alphalink.fr> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/net/ppp/ppp_generic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -2275,8 +2275,6 @@ ppp_unregister_channel(struct ppp_channe 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); @@ -2883,6 +2881,9 @@ ppp_disconnect_channel(struct channel *p */ 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) {
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