[PATCH 4.6 03/56] ppp: defer netns reference release for ppp channel

[Greg Kroah-Hartman]

4.6-stable review patch.  If anyone has any objections, please let me know.

--

From: WANG Cong 

[ Upstream commit 205e1e255c479f3fd77446415706463b282f94e4 ]

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-...@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: Greg Kroah-Hartman 
---
 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
@@ -2404,8 +2404,6 @@ ppp_unregister_channel(struct ppp_channe
spin_lock_bh(>all_channels_lock);
list_del(>list);
spin_unlock_bh(>all_channels_lock);
-   put_net(pch->chan_net);
-   pch->chan_net = NULL;
 
pch->file.dead = 1;
wake_up_interruptible(>file.rwait);
@@ -2999,6 +2997,9 @@ 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(_count);
 
if (!pch->file.dead) {

[PATCH 4.6 03/56] ppp: defer netns reference release for ppp channel

[Greg Kroah-Hartman]

4.6-stable review patch.  If anyone has any objections, please let me know.

--

From: WANG Cong 

[ Upstream commit 205e1e255c479f3fd77446415706463b282f94e4 ]

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-...@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: Greg Kroah-Hartman 
---
 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
@@ -2404,8 +2404,6 @@ ppp_unregister_channel(struct ppp_channe
spin_lock_bh(>all_channels_lock);
list_del(>list);
spin_unlock_bh(>all_channels_lock);
-   put_net(pch->chan_net);
-   pch->chan_net = NULL;
 
pch->file.dead = 1;
wake_up_interruptible(>file.rwait);
@@ -2999,6 +2997,9 @@ 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(_count);
 
if (!pch->file.dead) {