4.13-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit 50317fce2cc70a2bbbc4b42c31bbad510382a53c ]
Davide found the following script triggers a NULL pointer dereference:
ip l a name eth0 type dummy tc q a dev eth0 parent :1 handle 1: htb
This is because for a freshly created netdevice noop_qdisc is attached and when passing 'parent :1', kernel actually tries to match the major handle which is 0 and noop_qdisc has handle 0 so is matched by mistake. Commit 69012ae425d7 tries to fix a similar bug but still misses this case.
Handle 0 is not a valid one, should be just skipped. In fact, kernel uses it as TC_H_UNSPEC.
Fixes: 69012ae425d7 ("net: sched: fix handling of singleton qdiscs with qdisc_hash") Fixes: 59cc1f61f09c ("net: sched:convert qdisc linked list to hashtable") Reported-by: Davide Caratti dcaratti@redhat.com Cc: Jiri Kosina jkosina@suse.cz Cc: Eric Dumazet edumazet@google.com Cc: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/sch_api.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -307,6 +307,8 @@ struct Qdisc *qdisc_lookup(struct net_de { struct Qdisc *q;
+ if (!handle) + return NULL; q = qdisc_match_from_root(dev->qdisc, handle); if (q) goto out;