On Thu, 2017-10-26 at 10:17 -0700, Jeff Kirsher wrote: > From: Jesus Sanchez-Palencia <jesus.sanchez-palen...@intel.com> > > In qdisc_alloc() the dev_queue pointer was used without any checks > being performed. If qdisc_create() gets a null dev_queue pointer, it > just passes it along to qdisc_alloc(), leading to a crash. That > happens if a root qdisc implements select_queue() and returns a null > dev_queue pointer for an "invalid handle", for example, or if the > dev_queue associated with the parent qdisc is null. > > This patch is in preparation for the next in this series, where > select_queue() is being added to mqprio and as it may return a null > dev_queue. > > Signed-off-by: Jesus Sanchez-Palencia <jesus.sanchez-palen...@intel.com> > Tested-by: Henrik Austad <hen...@austad.us> > Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com> > --- > net/sched/sch_generic.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-)
hello, I didn't notice this when I posted https://www.spinics.net/lists/netdev/ms g462986.html , about one hour later, targeting Dave's net tree. I saw similar issues, but in my setup dev_queue was a valid pointer, and dev was NULL. This made qdisc_alloc() dereference NULL, when accessing dev-> members in the function body before returning the newly allocated qdisc. So, in my understanding both tests are necessary, but a (very trivial) conflict will be generated when these two commits will be eventually merged together. I like this suggestion from Ivan: -- >8 -- diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index bf8c81e07c70..6bd1ae993326 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -603,8 +603,14 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, struct Qdisc *sch; unsigned int size = QDISC_ALIGN(sizeof(*sch)) + ops->priv_size; int err = -ENOBUFS; - struct net_device *dev = dev_queue->dev; + struct net_device *dev; + + if (!dev_queue || !dev_queue->dev) { + err = !dev_queue ? -EINVAL : -ENOENT; + goto errout; + } + dev = dev_queue->dev; p = kzalloc_node(size, GFP_KERNEL, netdev_queue_numa_node_read(dev_queue)); -- 8< -- and I volunteer for sending a v2 of 'net/sched: fix NULL pointer dereference in qdisc_alloc()' including this, targeting 'net' tree, with an appropriate tag. WDYT? regards, -- davide
