Since ppp_create_interface() is the only place[1] holding both ppp_mutex
and rtnl_lock(), we can reverse lock ordering to allow taking ppp_mutex
when rtnl_lock is already held.
This will be necessary for creating PPP interfaces from an rtnetlink
callback.
[1]: There may actually be exceptions. When operating on PPP channels,
ppp_ioctl() can call lower level ioctl callbacks (chan->ops->ioctl())
with ppp_mutex locked. More review would be necessary to ensure no such
callback would ever call rtnl_lock(). OTOH, with proper locking inside
the ->ioctl() callbacks, ppp_mutex might be removed entirely from this
part of the code.
Signed-off-by: Guillaume Nault <g.nault@xxxxxxxxxxxx>
---
drivers/net/ppp/ppp_generic.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index c81e257..8aaedb8 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -2796,8 +2796,8 @@ static int ppp_create_interface(struct net *net, struct file *file, int *unit)
*/
dev_net_set(dev, net);
- mutex_lock(&ppp_mutex);
rtnl_lock();
+ mutex_lock(&ppp_mutex);
mutex_lock(&pn->all_ppp_mutex);
if (file->private_data) {
@@ -2847,15 +2847,15 @@ static int ppp_create_interface(struct net *net, struct file *file, int *unit)
atomic_inc(&ppp_unit_count);
mutex_unlock(&pn->all_ppp_mutex);
- rtnl_unlock();
mutex_unlock(&ppp_mutex);
+ rtnl_unlock();
return 0;
out2:
mutex_unlock(&pn->all_ppp_mutex);
- rtnl_unlock();
mutex_unlock(&ppp_mutex);
+ rtnl_unlock();
free_netdev(dev);
out1:
return ret;
--
2.8.0.rc3
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