3.2.52-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
[ Upstream commit d0fe8c888b1fd1a2f84b9962cabcb98a70988aec ]
I've been hitting a NULL ptr deref while using netconsole because the
np->dev check and the pointer manipulation in netpoll_cleanup are done
without rtnl and the following sequence happens when having a netconsole
over a vlan and we remove the vlan while disabling the netconsole:
CPU 1 CPU2
removes vlan and calls the notifier
enters store_enabled(), calls
netdev_cleanup which checks np->dev
and then waits for rtnl
executes the netconsole netdev
release notifier making np->dev
== NULL and releases rtnl
continues to dereference a member of
np->dev which at this point is == NULL
Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
net/core/netpoll.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index db4bb7a..9649cea 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -923,15 +923,14 @@ EXPORT_SYMBOL_GPL(__netpoll_cleanup);
void netpoll_cleanup(struct netpoll *np)
{
- if (!np->dev)
- return;
-
rtnl_lock();
+ if (!np->dev)
+ goto out;
__netpoll_cleanup(np);
- rtnl_unlock();
-
dev_put(np->dev);
np->dev = NULL;
+out:
+ rtnl_unlock();
}
EXPORT_SYMBOL(netpoll_cleanup);
--
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