tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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macsec: fix UAF bug for real_dev

Create a new macsec device but not get reference to real_dev. That can
not ensure that real_dev is freed after macsec. That will trigger the
UAF bug for real_dev as following:

==================================================================
BUG: KASAN: use-after-free in macsec_get_iflink+0x5f/0x70 drivers/net/macsec.c:3662
Call Trace:
...
macsec_get_iflink+0x5f/0x70 drivers/net/macsec.c:3662
dev_get_iflink+0x73/0xe0 net/core/dev.c:637
default_operstate net/core/link_watch.c:42 [inline]
rfc2863_policy+0x233/0x2d0 net/core/link_watch.c:54
linkwatch_do_dev+0x2a/0x150 net/core/link_watch.c:161

Allocated by task 22209:
...
alloc_netdev_mqs+0x98/0x1100 net/core/dev.c:10549
rtnl_create_link+0x9d7/0xc00 net/core/rtnetlink.c:3235
veth_newlink+0x20e/0xa90 drivers/net/veth.c:1748

Freed by task 8:
...
kfree+0xd6/0x4d0 mm/slub.c:4552
kvfree+0x42/0x50 mm/util.c:615
device_release+0x9f/0x240 drivers/base/core.c:2229
kobject_cleanup lib/kobject.c:673 [inline]
kobject_release lib/kobject.c:704 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x1c8/0x540 lib/kobject.c:721
netdev_run_todo+0x72e/0x10b0 net/core/dev.c:10327

After commit faab39f63c1f ("net: allow out-of-order netdev unregistration")
and commit e5f80fcf869a ("ipv6: give an IPv6 dev to blackhole_netdev"), we
can add dev_hold_track() in macsec_dev_init() and dev_put_track() in
macsec_free_netdev() to fix the problem.

Fixes: 2bce1ebed17d ("macsec: fix refcnt leak in module exit routine")
Reported-by: syzbot+d0e94b65ac259c29ce7a@syzkaller.appspotmail.com
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Link: https://lore.kernel.org/r/20220531074500.1272846-1-william.xuanziyang@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

authored by

Ziyang Xuan and committed by
Paolo Abeni 196a888c f3d671c7

+7
+7
drivers/net/macsec.c
··· 99 99 * struct macsec_dev - private data 100 100 * @secy: SecY config 101 101 * @real_dev: pointer to underlying netdevice 102 + * @dev_tracker: refcount tracker for @real_dev reference 102 103 * @stats: MACsec device stats 103 104 * @secys: linked list of SecY's on the underlying device 104 105 * @gro_cells: pointer to the Generic Receive Offload cell ··· 108 107 struct macsec_dev { 109 108 struct macsec_secy secy; 110 109 struct net_device *real_dev; 110 + netdevice_tracker dev_tracker; 111 111 struct pcpu_secy_stats __percpu *stats; 112 112 struct list_head secys; 113 113 struct gro_cells gro_cells; ··· 3461 3459 if (is_zero_ether_addr(dev->broadcast)) 3462 3460 memcpy(dev->broadcast, real_dev->broadcast, dev->addr_len); 3463 3461 3462 + /* Get macsec's reference to real_dev */ 3463 + dev_hold_track(real_dev, &macsec->dev_tracker, GFP_KERNEL); 3464 + 3464 3465 return 0; 3465 3466 } 3466 3467 ··· 3709 3704 free_percpu(macsec->stats); 3710 3705 free_percpu(macsec->secy.tx_sc.stats); 3711 3706 3707 + /* Get rid of the macsec's reference to real_dev */ 3708 + dev_put_track(macsec->real_dev, &macsec->dev_tracker); 3712 3709 } 3713 3710 3714 3711 static void macsec_setup(struct net_device *dev)