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 <dcara...@redhat.com>
Cc: Jiri Kosina <jkos...@suse.cz>
Cc: Eric Dumazet <eduma...@google.com>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
net/sched/sch_api.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index c6deb74e3d2f..22bc6fc48311 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -301,6 +301,8 @@ struct Qdisc *qdisc_lookup(struct net_device *dev, u32
handle)
{
struct Qdisc *q;
+ if (!handle)
+ return NULL;
q = qdisc_match_from_root(dev->qdisc, handle);
if (q)
goto out;
--
2.13.0
