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Message-ID: <20120718122106.GB25563@hmsreliant.think-freely.org>
Date: Wed, 18 Jul 2012 08:21:06 -0400
From: Neil Horman <nhorman@...driver.com>
To: John Fastabend <john.r.fastabend@...el.com>
Cc: Gao feng <gaofeng@...fujitsu.com>, eric.dumazet@...il.com,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
davem@...emloft.net, Eric Dumazet <edumazet@...gle.com>,
"Rustad, Mark D" <mark.d.rustad@...el.com>
Subject: Re: [PATCH v4] net: cgroup: fix access the unallocated memory in
netprio cgroup
On Tue, Jul 17, 2012 at 01:47:25PM -0700, John Fastabend wrote:
> On 7/12/2012 12:50 AM, Gao feng wrote:
> >there are some out of bound accesses in netprio cgroup.
> >
> >now before accessing the dev->priomap.priomap array,we only check
> >if the dev->priomap exist.and because we don't want to see
> >additional bound checkings in fast path, so we should make sure
> >that dev->priomap is null or array size of dev->priomap.priomap
> >is equal to max_prioidx + 1;
> >
> >so in write_priomap logic,we should call extend_netdev_table when
> >dev->priomap is null and dev->priomap.priomap_len < max_len.
> >and in cgrp_create->update_netdev_tables logic,we should call
> >extend_netdev_table only when dev->priomap exist and
> >dev->priomap.priomap_len < max_len.
> >
> >and it's not needed to call update_netdev_tables in write_priomap,
> >we can only allocate the net device's priomap which we change through
> >net_prio.ifpriomap.
> >
> >this patch also add a return value for update_netdev_tables &
> >extend_netdev_table, so when new_priomap is allocated failed,
> >write_priomap will stop to access the priomap,and return -ENOMEM
> >back to the userspace to tell the user what happend.
> >
> >Change From v3:
> >1. add rtnl protect when reading max_prioidx in write_priomap.
> >
> >2. only call extend_netdev_table when map->priomap_len < max_len,
> > this will make sure array size of dev->map->priomap always
> > bigger than any prioidx.
> >
> >3. add a function write_update_netdev_table to make codes clear.
> >
> >Change From v2:
> >1. protect extend_netdev_table by RTNL.
> >2. when extend_netdev_table failed,call dev_put to reduce device's refcount.
> >
> >Signed-off-by: Gao feng <gaofeng@...fujitsu.com>
> >Cc: Neil Horman <nhorman@...driver.com>
> >Cc: Eric Dumazet <edumazet@...gle.com>
> >---
> > net/core/netprio_cgroup.c | 71 ++++++++++++++++++++++++++++++++++-----------
> > 1 files changed, 54 insertions(+), 17 deletions(-)
> >
>
> [...]
>
> >+
> >+static int update_netdev_tables(void)
> >+{
> >+ int ret = 0;
> > struct net_device *dev;
> >- u32 max_len = atomic_read(&max_prioidx) + 1;
> >+ u32 max_len;
> > struct netprio_map *map;
>
>
> need to check if net subsystem is initialized before we try
> to use it here...
>
> if (some_check) -> need to lookup what this check is
> return ret;
>
> >
> > rtnl_lock();
> >+ max_len = atomic_read(&max_prioidx) + 1;
> > for_each_netdev(&init_net, dev) {
> > map = rtnl_dereference(dev->priomap);
> >- if ((!map) ||
> >- (map->priomap_len < max_len))
> >- extend_netdev_table(dev, max_len);
> >+ /*
> >+ * don't allocate priomap if we didn't
> >+ * change net_prio.ifpriomap (map == NULL),
> >+ * this will speed up skb_update_prio.
> >+ */
> >+ if (map && map->priomap_len < max_len) {
> >+ ret = extend_netdev_table(dev, max_len);
> >+ if (ret < 0)
> >+ break;
> >+ }
> > }
> > rtnl_unlock();
> >+ return ret;
> > }
> >
> > static struct cgroup_subsys_state *cgrp_create(struct cgroup *cgrp)
> > {
> > struct cgroup_netprio_state *cs;
> >- int ret;
> >+ int ret = -EINVAL;
> >
> > cs = kzalloc(sizeof(*cs), GFP_KERNEL);
> > if (!cs)
> > return ERR_PTR(-ENOMEM);
> >
> >- if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx) {
> >- kfree(cs);
> >- return ERR_PTR(-EINVAL);
> >- }
> >+ if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx)
> >+ goto out;
> >
> > ret = get_prioidx(&cs->prioidx);
> >- if (ret != 0) {
> >+ if (ret < 0) {
> > pr_warn("No space in priority index array\n");
> >- kfree(cs);
> >- return ERR_PTR(ret);
> >+ goto out;
> >+ }
> >+
> >+ ret = update_netdev_tables();
> >+ if (ret < 0) {
> >+ put_prioidx(cs->prioidx);
> >+ goto out;
> > }
>
> Gao,
>
> This introduces a null ptr dereference when netprio_cgroup is built
> into the kernel because update_netdev_tables() depends on init_net.
> However cgrp_create is being called by cgroup_init before
> do_initcalls() is called and before net_dev_init().
>
> .John
>
Not sure I follow here John. Shouldn't init_net be initialized prior to any
network devices getting registered? In other words, shouldn't for_each_netdev
just result in zero iterations through the loop?
Neil
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