Re: [PATCH wpan] mac802154: fix llsec key resources release in mac802154_llsec_key_del

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Hello.

On 28.02.24 17:38, Fedor Pchelkin 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@xxxxxxxxxxxxxxx
Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>

This patch has been applied to the wpan-next tree and will be
part of the next pull request to net-next. Thanks!

regards
Stefan Schmidt




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