net/sched: unregister lockdep keys in qdisc_create/qdisc_alloc error path

Naresh and Eric report several errors (corrupted elements in the dynamic
key hash list), when running tdc.py or syzbot. The error path of
qdisc_alloc() and qdisc_create() frees the qdisc memory, but it forgets
to unregister the lockdep key, thus causing use-after-free like the
following one:

 ==================================================================
 BUG: KASAN: slab-use-after-free in lockdep_register_key+0x5f2/0x700
 Read of size 8 at addr ffff88811236f2a8 by task ip/7925

 CPU: 26 PID: 7925 Comm: ip Kdump: loaded Not tainted 6.9.0-rc2+ #648
 Hardware name: Supermicro SYS-6027R-72RF/X9DRH-7TF/7F/iTF/iF, BIOS 3.0  07/26/2013
 Call Trace:
  <TASK>
  dump_stack_lvl+0x7c/0xc0
  print_report+0xc9/0x610
  kasan_report+0x89/0xc0
  lockdep_register_key+0x5f2/0x700
  qdisc_alloc+0x21d/0xb60
  qdisc_create_dflt+0x63/0x3c0
  attach_one_default_qdisc.constprop.37+0x8e/0x170
  dev_activate+0x4bd/0xc30
  __dev_open+0x275/0x380
  __dev_change_flags+0x3f1/0x570
  dev_change_flags+0x7c/0x160
  do_setlink+0x1ea1/0x34b0
  __rtnl_newlink+0x8c9/0x1510
  rtnl_newlink+0x61/0x90
  rtnetlink_rcv_msg+0x2f0/0xbc0
  netlink_rcv_skb+0x120/0x380
  netlink_unicast+0x420/0x630
  netlink_sendmsg+0x732/0xbc0
  __sock_sendmsg+0x1ea/0x280
  ____sys_sendmsg+0x5a9/0x990
  ___sys_sendmsg+0xf1/0x180
  __sys_sendmsg+0xd3/0x180
  do_syscall_64+0x96/0x180
  entry_SYSCALL_64_after_hwframe+0x71/0x79
 RIP: 0033:0x7f9503f4fa07
 Code: 0a 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b9 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 89 74 24 10
 RSP: 002b:00007fff6c729068 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
 RAX: ffffffffffffffda RBX: 000000006630c681 RCX: 00007f9503f4fa07
 RDX: 0000000000000000 RSI: 00007fff6c7290d0 RDI: 0000000000000003
 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000078
 R10: 000000000000009b R11: 0000000000000246 R12: 0000000000000001
 R13: 00007fff6c729180 R14: 0000000000000000 R15: 000055bf67dd9040
  </TASK>

 Allocated by task 7745:
  kasan_save_stack+0x1c/0x40
  kasan_save_track+0x10/0x30
  __kasan_kmalloc+0x7b/0x90
  __kmalloc_node+0x1ff/0x460
  qdisc_alloc+0xae/0xb60
  qdisc_create+0xdd/0xfb0
  tc_modify_qdisc+0x37e/0x1960
  rtnetlink_rcv_msg+0x2f0/0xbc0
  netlink_rcv_skb+0x120/0x380
  netlink_unicast+0x420/0x630
  netlink_sendmsg+0x732/0xbc0
  __sock_sendmsg+0x1ea/0x280
  ____sys_sendmsg+0x5a9/0x990
  ___sys_sendmsg+0xf1/0x180
  __sys_sendmsg+0xd3/0x180
  do_syscall_64+0x96/0x180
  entry_SYSCALL_64_after_hwframe+0x71/0x79

 Freed by task 7745:
  kasan_save_stack+0x1c/0x40
  kasan_save_track+0x10/0x30
  kasan_save_free_info+0x36/0x60
  __kasan_slab_free+0xfe/0x180
  kfree+0x113/0x380
  qdisc_create+0xafb/0xfb0
  tc_modify_qdisc+0x37e/0x1960
  rtnetlink_rcv_msg+0x2f0/0xbc0
  netlink_rcv_skb+0x120/0x380
  netlink_unicast+0x420/0x630
  netlink_sendmsg+0x732/0xbc0
  __sock_sendmsg+0x1ea/0x280
  ____sys_sendmsg+0x5a9/0x990
  ___sys_sendmsg+0xf1/0x180
  __sys_sendmsg+0xd3/0x180
  do_syscall_64+0x96/0x180
  entry_SYSCALL_64_after_hwframe+0x71/0x79

Fix this ensuring that lockdep_unregister_key() is called before the
qdisc struct is freed, also in the error path of qdisc_create() and
qdisc_alloc().

Fixes: af0cb3fa ("net/sched: fix false lockdep warning on qdisc root lock")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/netdev/20240429221706.1492418-1-naresh.kamboju@linaro.org/Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/2aa1ca0c0a3aa0acc15925c666c777a4b5de553c.1714496886.git.dcaratti@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/sched/sch_api.c

@@ -1389,6 +1389,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 		ops->destroy(sch);
 	qdisc_put_stab(rtnl_dereference(sch->stab));
 err_out3:
+	lockdep_unregister_key(&sch->root_lock_key);
 	netdev_put(dev, &sch->dev_tracker);
 	qdisc_free(sch);
 err_out2:

net/sched/sch_generic.c

@@ -982,6 +982,7 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 
 	return sch;
 errout1:
+	lockdep_unregister_key(&sch->root_lock_key);
 	kfree(sch);
 errout:
 	return ERR_PTR(err);