From: Vlad Buslov vladbu@mellanox.com
[ Upstream commit 6f99528e9797794b91b43321fbbc93fe772b0803 ]
Rtnl lock is encapsulated in netlink and cannot be accessed by other modules directly. This means that reference counted objects that rely on rtnl lock cannot use it with refcounter helper function that atomically releases decrements reference and obtains mutex.
This patch implements simple wrapper function around refcount_dec_and_lock that obtains rtnl lock if reference counter value reached 0.
Signed-off-by: Vlad Buslov vladbu@mellanox.com Acked-by: Jiri Pirko jiri@mellanox.com Signed-off-by: David S. Miller davem@davemloft.net [Lee: Sent to Stable] Link: https://syzkaller.appspot.com/bug?id=d7e411c5472dd5da33d8cc921ccadc747743a56... Reported-by: syzbot+5f229e48cccc804062c0@syzkaller.appspotmail.com Signed-off-by: Lee Jones lee.jones@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/rtnetlink.h | 2 ++ net/core/rtnetlink.c | 6 ++++++ 2 files changed, 8 insertions(+)
--- a/include/linux/rtnetlink.h +++ b/include/linux/rtnetlink.h @@ -6,6 +6,7 @@ #include <linux/mutex.h> #include <linux/netdevice.h> #include <linux/wait.h> +#include <linux/refcount.h> #include <uapi/linux/rtnetlink.h>
extern int rtnetlink_send(struct sk_buff *skb, struct net *net, u32 pid, u32 group, int echo); @@ -34,6 +35,7 @@ extern void rtnl_unlock(void); extern int rtnl_trylock(void); extern int rtnl_is_locked(void); extern int rtnl_lock_killable(void); +extern bool refcount_dec_and_rtnl_lock(refcount_t *r);
extern wait_queue_head_t netdev_unregistering_wq; extern struct rw_semaphore pernet_ops_rwsem; --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -130,6 +130,12 @@ int rtnl_is_locked(void) } EXPORT_SYMBOL(rtnl_is_locked);
+bool refcount_dec_and_rtnl_lock(refcount_t *r) +{ + return refcount_dec_and_mutex_lock(r, &rtnl_mutex); +} +EXPORT_SYMBOL(refcount_dec_and_rtnl_lock); + #ifdef CONFIG_PROVE_LOCKING bool lockdep_rtnl_is_held(void) {