[lvc-project] [PATCH wpan] mac802154: fix llsec key resources release in mac802154_llsec_key_del

[Alexander Aring]

Hi,

On Mon, Mar 4, 2024 at 2:25 AM Fedor Pchelkin <pchelkin at ispras.ru> wrote:
>
> Hello Alexander,
>
> Thanks for review!
>
> On 24/03/03 06:19PM, Alexander Aring wrote:
> > Hi,
> >
> > On Wed, Feb 28, 2024 at 11:44 AM Fedor Pchelkin <pchelkin at ispras.ru> wrote:
> > >
> > > mac802154_llsec_key_del() can free resources of a key directly without
> > > following the RCU rules for waiting before the end of a grace period. This
> > > may lead to use-after-free in case llsec_lookup_key() is traversing the
> > > list of keys in parallel with a key deletion:
> > >
> > > refcount_t: addition on 0; use-after-free.
> > > WARNING: CPU: 4 PID: 16000 at lib/refcount.c:25 refcount_warn_saturate+0x162/0x2a0
> > > Modules linked in:
> > > CPU: 4 PID: 16000 Comm: wpan-ping Not tainted 6.7.0 #19
> > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > > RIP: 0010:refcount_warn_saturate+0x162/0x2a0
> > > Call Trace:
> > >  <TASK>
> > >  llsec_lookup_key.isra.0+0x890/0x9e0
> > >  mac802154_llsec_encrypt+0x30c/0x9c0
> > >  ieee802154_subif_start_xmit+0x24/0x1e0
> > >  dev_hard_start_xmit+0x13e/0x690
> > >  sch_direct_xmit+0x2ae/0xbc0
> > >  __dev_queue_xmit+0x11dd/0x3c20
> > >  dgram_sendmsg+0x90b/0xd60
> > >  __sys_sendto+0x466/0x4c0
> > >  __x64_sys_sendto+0xe0/0x1c0
> > >  do_syscall_64+0x45/0xf0
> > >  entry_SYSCALL_64_after_hwframe+0x6e/0x76
> > >
> > > Also, ieee802154_llsec_key_entry structures are not freed by
> > > mac802154_llsec_key_del():
> > >
> > > unreferenced object 0xffff8880613b6980 (size 64):
> > >   comm "iwpan", pid 2176, jiffies 4294761134 (age 60.475s)
> > >   hex dump (first 32 bytes):
> > >     78 0d 8f 18 80 88 ff ff 22 01 00 00 00 00 ad de  x.......".......
> > >     00 00 00 00 00 00 00 00 03 00 cd ab 00 00 00 00  ................
> > >   backtrace:
> > >     [<ffffffff81dcfa62>] __kmem_cache_alloc_node+0x1e2/0x2d0
> > >     [<ffffffff81c43865>] kmalloc_trace+0x25/0xc0
> > >     [<ffffffff88968b09>] mac802154_llsec_key_add+0xac9/0xcf0
> > >     [<ffffffff8896e41a>] ieee802154_add_llsec_key+0x5a/0x80
> > >     [<ffffffff8892adc6>] nl802154_add_llsec_key+0x426/0x5b0
> > >     [<ffffffff86ff293e>] genl_family_rcv_msg_doit+0x1fe/0x2f0
> > >     [<ffffffff86ff46d1>] genl_rcv_msg+0x531/0x7d0
> > >     [<ffffffff86fee7a9>] netlink_rcv_skb+0x169/0x440
> > >     [<ffffffff86ff1d88>] genl_rcv+0x28/0x40
> > >     [<ffffffff86fec15c>] netlink_unicast+0x53c/0x820
> > >     [<ffffffff86fecd8b>] netlink_sendmsg+0x93b/0xe60
> > >     [<ffffffff86b91b35>] ____sys_sendmsg+0xac5/0xca0
> > >     [<ffffffff86b9c3dd>] ___sys_sendmsg+0x11d/0x1c0
> > >     [<ffffffff86b9c65a>] __sys_sendmsg+0xfa/0x1d0
> > >     [<ffffffff88eadbf5>] do_syscall_64+0x45/0xf0
> > >     [<ffffffff890000ea>] entry_SYSCALL_64_after_hwframe+0x6e/0x76
> > >
> > > Handle the proper resource release in the RCU callback function
> > > mac802154_llsec_key_del_rcu().
> > >
> > > Note that if llsec_lookup_key() finds a key, it gets a refcount via
> > > llsec_key_get() and locally copies key id from key_entry (which is a
> > > list element). So it's safe to call llsec_key_put() and free the list
> > > entry after the RCU grace period elapses.
> > >
> > > Found by Linux Verification Center (linuxtesting.org).
> > >
> > > Fixes: 5d637d5aabd8 ("mac802154: add llsec structures and mutators")
> > > Cc: stable at vger.kernel.org
> > > Signed-off-by: Fedor Pchelkin <pchelkin at ispras.ru>
> > > ---
> > > Should the patch be targeted to "net" tree directly?
> > >
> > >  include/net/cfg802154.h |  1 +
> > >  net/mac802154/llsec.c   | 18 +++++++++++++-----
> > >  2 files changed, 14 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
> > > index cd95711b12b8..76d2cd2e2b30 100644
> > > --- a/include/net/cfg802154.h
> > > +++ b/include/net/cfg802154.h
> > > @@ -401,6 +401,7 @@ struct ieee802154_llsec_key {
> > >
> > >  struct ieee802154_llsec_key_entry {
> > >         struct list_head list;
> > > +       struct rcu_head rcu;
> > >
> > >         struct ieee802154_llsec_key_id id;
> > >         struct ieee802154_llsec_key *key;
> > > diff --git a/net/mac802154/llsec.c b/net/mac802154/llsec.c
> > > index 8d2eabc71bbe..f13b07ebfb98 100644
> > > --- a/net/mac802154/llsec.c
> > > +++ b/net/mac802154/llsec.c
> > > @@ -265,19 +265,27 @@ int mac802154_llsec_key_add(struct mac802154_llsec *sec,
> > >         return -ENOMEM;
> > >  }
> > >
> > > +static void mac802154_llsec_key_del_rcu(struct rcu_head *rcu)
> > > +{
> > > +       struct ieee802154_llsec_key_entry *pos;
> > > +       struct mac802154_llsec_key *mkey;
> > > +
> > > +       pos = container_of(rcu, struct ieee802154_llsec_key_entry, rcu);
> > > +       mkey = container_of(pos->key, struct mac802154_llsec_key, key);
> > > +
> > > +       llsec_key_put(mkey);
> > > +       kfree_sensitive(pos);
> >
> > I don't think this kfree is right, "struct ieee802154_llsec_key_entry"
> > is declared as "non pointer" in "struct mac802154_llsec_key". The
> > memory that is part of "struct ieee802154_llsec_key_entry" should be
> > freed when llsec_key_put(), llsec_key_release() hits.
> >
> > Or is there something I am missing here?
>
> `struct ieee802154_llsec_key_entry` is not included into any other
> struct. It is a standalone entity describing an entry in the
> `ieee802154_llsec_table.keys` list.
>
> Maybe you are confusing it with `struct ieee802154_llsec_key`?
>

Yes, I was confused about "ieee802154_llsec_key_entry" vs
"ieee802154_llsec_key".

Acked-by: Alexander Aring <aahringo at redhat.com>

Thanks.

- Alex