Commit message: net: sched: fix use-after-free in tc_new_tfilter()

Whenever tc_new_tfilter() jumps back to replay: label,
we need to make sure @q and @chain local variables are cleared again,
or risk use-after-free as in [1]

For consistency, apply the same fix in tc_ctl_chain()

BUG: KASAN: use-after-free in mini_qdisc_pair_swap+0x1b9/0x1f0 net/sched/sch_generic.c:1581
Write of size 8 at addr ffff8880985c4b08 by task syz-executor.4/1945

CPU: 0 PID: 1945 Comm: syz-executor.4 Not tainted 5.17.0-rc1-syzkaller-00495-gff58831fa02d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
 __kasan_report mm/kasan/report.c:442 [inline]
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
 mini_qdisc_pair_swap+0x1b9/0x1f0 net/sched/sch_generic.c:1581
 tcf_chain_head_change_item net/sched/cls_api.c:372 [inline]
 tcf_chain0_head_change.isra.0+0xb9/0x120 net/sched/cls_api.c:386
 tcf_chain_tp_insert net/sched/cls_api.c:1657 [inline]
 tcf_chain_tp_insert_unique net/sched/cls_api.c:1707 [inline]
 tc_new_tfilter+0x1e67/0x2350 net/sched/cls_api.c:2086
 rtnetlink_rcv_msg+0x80d/0xb80 net/core/rtnetlink.c:5583
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
 netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
 netlink_unicast+0x539/0x7e0 net/netlink/af_netlink.c:1343
 netlink_sendmsg+0x904/0xe00 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:705 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:725
 ____sys_sendmsg+0x331/0x810 net/socket.c:2413
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2467
 __sys_sendmmsg+0x195/0x470 net/socket.c:2553
 __do_sys_sendmmsg net/socket.c:2582 [inline]
 __se_sys_sendmmsg net/socket.c:2579 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2579
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f2647172059
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2645aa5168 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f2647285100 RCX: 00007f2647172059
RDX: 040000000000009f RSI: 00000000200002c0 RDI: 0000000000000006
RBP: 00007f26471cc08d R08: 0000000000000000 R09: 0000000000000000
R10: 9e00000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fffb3f7f02f R14: 00007f2645aa5300 R15: 0000000000022000
 </TASK>

Allocated by task 1944:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:436 [inline]
 ____kasan_kmalloc mm/kasan/common.c:515 [inline]
 ____kasan_kmalloc mm/kasan/common.c:474 [inline]
 __kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:524
 kmalloc_node include/linux/slab.h:604 [inline]
 kzalloc_node include/linux/slab.h:726 [inline]
 qdisc_alloc+0xac/0xa10 net/sched/sch_generic.c:941
 qdisc_create.constprop.0+0xce/0x10f0 net/sched/sch_api.c:1211
 tc_modify_qdisc+0x4c5/0x1980 net/sched/sch_api.c:1660
 rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5592
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
 netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
 netlink_unicast+0x539/0x7e0 net/netlink/af_netlink.c:1343
 netlink_sendmsg+0x904/0xe00 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:705 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:725
 ____sys_sendmsg+0x331/0x810 net/socket.c:2413
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2467
 __sys_sendmmsg+0x195/0x470 net/socket.c:2553
 __do_sys_sendmmsg net/socket.c:2582 [inline]
 __se_sys_sendmmsg net/socket.c:2579 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2579
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 3609:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track+0x21/0x30 mm/kasan/common.c:45
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
 ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
 kasan_slab_free include/linux/kasan.h:236 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
 slab_free mm/slub.c:3509 [inline]
 kfree+0xcb/0x280 mm/slub.c:4562
 rcu_do_batch kernel/rcu/tree.c:2527 [inline]
 rcu_core+0x7b8/0x1540 kernel/rcu/tree.c:2778
 __do_softirq+0x29b/0x9c2 kernel/softirq.c:558

Last potentially related work creation:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xbe/0xd0 mm/kasan/generic.c:348
 __call_rcu kernel/rcu/tree.c:3026 [inline]
 call_rcu+0xb1/0x740 kernel/rcu/tree.c:3106
 qdisc_put_unlocked+0x6f/0x90 net/sched/sch_generic.c:1109
 tcf_block_release+0x86/0x90 net/sched/cls_api.c:1238
 tc_new_tfilter+0xc0d/0x2350 net/sched/cls_api.c:2148
 rtnetlink_rcv_msg+0x80d/0xb80 net/core/rtnetlink.c:5583
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
 netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
 netlink_unicast+0x539/0x7e0 net/netlink/af_netlink.c:1343
 netlink_sendmsg+0x904/0xe00 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:705 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:725
 ____sys_sendmsg+0x331/0x810 net/socket.c:2413
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2467
 __sys_sendmmsg+0x195/0x470 net/socket.c:2553
 __do_sys_sendmmsg net/socket.c:2582 [inline]
 __se_sys_sendmmsg net/socket.c:2579 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2579
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff8880985c4800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 776 bytes inside of
 1024-byte region [ffff8880985c4800, ffff8880985c4c00)
The buggy address belongs to the page:
page:ffffea0002617000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x985c0
head:ffffea0002617000 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888010c41dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 1941, ts 1038999441284, free_ts 1033444432829
 prep_new_page mm/page_alloc.c:2434 [inline]
 get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
 alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
 alloc_slab_page mm/slub.c:1799 [inline]
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x28a/0x3b0 mm/slub.c:2004
 ___slab_alloc+0x87c/0xe90 mm/slub.c:3018
 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
 slab_alloc_node mm/slub.c:3196 [inline]
 slab_alloc mm/slub.c:3238 [inline]
 __kmalloc+0x2fb/0x340 mm/slub.c:4420
 kmalloc include/linux/slab.h:586 [inline]
 kzalloc include/linux/slab.h:715 [inline]
 __register_sysctl_table+0x112/0x1090 fs/proc/proc_sysctl.c:1335
 neigh_sysctl_register+0x2c8/0x5e0 net/core/neighbour.c:3787
 devinet_sysctl_register+0xb1/0x230 net/ipv4/devinet.c:2618
 inetdev_init+0x286/0x580 net/ipv4/devinet.c:278
 inetdev_event+0xa8a/0x15d0 net/ipv4/devinet.c:1532
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:84
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1919
 call_netdevice_notifiers_extack net/core/dev.c:1931 [inline]
 call_netdevice_notifiers net/core/dev.c:1945 [inline]
 register_netdevice+0x1073/0x1500 net/core/dev.c:9698
 veth_newlink+0x59c/0xa90 drivers/net/veth.c:1722
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1352 [inline]
 free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
 free_unref_page_prepare mm/page_alloc.c:3325 [inline]
 free_unref_page+0x19/0x690 mm/page_alloc.c:3404
 release_pages+0x748/0x1220 mm/swap.c:956
 tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
 tlb_flush_mmu+0xe9/0x6b0 mm/mmu_gather.c:250
 zap_pte_range mm/memory.c:1441 [inline]
 zap_pmd_range mm/memory.c:1490 [inline]
 zap_pud_range mm/memory.c:1519 [inline]
 zap_p4d_range mm/memory.c:1540 [inline]
 unmap_page_range+0x1d1d/0x2a30 mm/memory.c:1561
 unmap_single_vma+0x198/0x310 mm/memory.c:1606
 unmap_vmas+0x16b/0x2f0 mm/memory.c:1638
 exit_mmap+0x201/0x670 mm/mmap.c:3178
 __mmput+0x122/0x4b0 kernel/fork.c:1114
 mmput+0x56/0x60 kernel/fork.c:1135
 exit_mm kernel/exit.c:507 [inline]
 do_exit+0xa3c/0x2a30 kernel/exit.c:793
 do_group_exit+0xd2/0x2f0 kernel/exit.c:935
 __do_sys_exit_group kernel/exit.c:946 [inline]
 __se_sys_exit_group kernel/exit.c:944 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:944
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Memory state around the buggy address:
 ffff8880985c4a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880985c4a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880985c4b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8880985c4b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880985c4c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

Fixes: 470502de5bdb ("net: sched: unlock rules update API")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vlad Buslov <vladbu@mellanox.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Link: https://lore.kernel.org/r/20220131172018.3704490-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
CVE: CVE-2022-1055
CWE: CWE-416
Vulnerability description: A use-after-free exists in the Linux Kernel in tc_new_tfilter that could allow a local attacker to gain privilege escalation. The exploit requires unprivileged user namespaces. We recommend upgrading past commit 04c2a47ffb13c29778e2a14e414ad4cb5a5db4b5

Project: linux
File: cls_api.c

static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
			  struct netlink_ext_ack *extack)
{
	struct net *net = sock_net(skb->sk);
	struct nlattr *tca[TCA_MAX + 1];
	char name[IFNAMSIZ];
	struct tcmsg *t;
	u32 protocol;
	u32 prio;
	bool prio_allocate;
	u32 parent;
	u32 chain_index;
	struct Qdisc *q = NULL;
	struct tcf_chain_info chain_info;
	struct tcf_chain *chain = NULL;
	struct tcf_block *block;
	struct tcf_proto *tp;
	unsigned long cl;
	void *fh;
	int err;
	int tp_created;
	bool rtnl_held = false;
	u32 flags;

	if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
		return -EPERM;

replay:
	tp_created = 0;

	err = nlmsg_parse_deprecated(n, sizeof(*t), tca, TCA_MAX,
				     rtm_tca_policy, extack);
	if (err < 0)
		return err;

	t = nlmsg_data(n);
	protocol = TC_H_MIN(t->tcm_info);
	prio = TC_H_MAJ(t->tcm_info);
	prio_allocate = false;
	parent = t->tcm_parent;
	tp = NULL;
	cl = 0;
	block = NULL;
	flags = 0;

	if (prio == 0) {
		/* If no priority is provided by the user,
		 * we allocate one.
		 */
		if (n->nlmsg_flags & NLM_F_CREATE) {
			prio = TC_H_MAKE(0x80000000U, 0U);
			prio_allocate = true;
		} else {
			NL_SET_ERR_MSG(extack, "Invalid filter command with priority of zero");
			return -ENOENT;
		}
	}

	/* Find head of filter chain. */

	err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
	if (err)
		return err;

	if (tcf_proto_check_kind(tca[TCA_KIND], name)) {
		NL_SET_ERR_MSG(extack, "Specified TC filter name too long");
		err = -EINVAL;
		goto errout;
	}

	/* Take rtnl mutex if rtnl_held was set to true on previous iteration,
	 * block is shared (no qdisc found), qdisc is not unlocked, classifier
	 * type is not specified, classifier is not unlocked.
	 */
	if (rtnl_held ||
	    (q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
	    !tcf_proto_is_unlocked(name)) {
		rtnl_held = true;
		rtnl_lock();
	}

	err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
	if (err)
		goto errout;

	block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
				 extack);
	if (IS_ERR(block)) {
		err = PTR_ERR(block);
		goto errout;
	}
	block->classid = parent;

	chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
	if (chain_index > TC_ACT_EXT_VAL_MASK) {
		NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit");
		err = -EINVAL;
		goto errout;
	}
	chain = tcf_chain_get(block, chain_index, true);
	if (!chain) {
		NL_SET_ERR_MSG(extack, "Cannot create specified filter chain");
		err = -ENOMEM;
		goto errout;
	}

	mutex_lock(&chain->filter_chain_lock);
	tp = tcf_chain_tp_find(chain, &chain_info, protocol,
			       prio, prio_allocate);
	if (IS_ERR(tp)) {
		NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
		err = PTR_ERR(tp);
		goto errout_locked;
	}

	if (tp == NULL) {
		struct tcf_proto *tp_new = NULL;

		if (chain->flushing) {
			err = -EAGAIN;
			goto errout_locked;
		}

		/* Proto-tcf does not exist, create new one */

		if (tca[TCA_KIND] == NULL || !protocol) {
			NL_SET_ERR_MSG(extack, "Filter kind and protocol must be specified");
			err = -EINVAL;
			goto errout_locked;
		}

		if (!(n->nlmsg_flags & NLM_F_CREATE)) {
			NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
			err = -ENOENT;
			goto errout_locked;
		}

		if (prio_allocate)
			prio = tcf_auto_prio(tcf_chain_tp_prev(chain,
							       &chain_info));

		mutex_unlock(&chain->filter_chain_lock);
		tp_new = tcf_proto_create(name, protocol, prio, chain,
					  rtnl_held, extack);
		if (IS_ERR(tp_new)) {
			err = PTR_ERR(tp_new);
			goto errout_tp;
		}

		tp_created = 1;
		tp = tcf_chain_tp_insert_unique(chain, tp_new, protocol, prio,
						rtnl_held);
		if (IS_ERR(tp)) {
			err = PTR_ERR(tp);
			goto errout_tp;
		}
	} else {
		mutex_unlock(&chain->filter_chain_lock);
	}

	if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
		NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
		err = -EINVAL;
		goto errout;
	}

	fh = tp->ops->get(tp, t->tcm_handle);

	if (!fh) {
		if (!(n->nlmsg_flags & NLM_F_CREATE)) {
			NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
			err = -ENOENT;
			goto errout;
		}
	} else if (n->nlmsg_flags & NLM_F_EXCL) {
		tfilter_put(tp, fh);
		NL_SET_ERR_MSG(extack, "Filter already exists");
		err = -EEXIST;
		goto errout;
	}

	if (chain->tmplt_ops && chain->tmplt_ops != tp->ops) {
		NL_SET_ERR_MSG(extack, "Chain template is set to a different filter kind");
		err = -EINVAL;
		goto errout;
	}

	if (!(n->nlmsg_flags & NLM_F_CREATE))
		flags |= TCA_ACT_FLAGS_REPLACE;
	if (!rtnl_held)
		flags |= TCA_ACT_FLAGS_NO_RTNL;
	err = tp->ops->change(net, skb, tp, cl, t->tcm_handle, tca, &fh,
			      flags, extack);
	if (err == 0) {
		tfilter_notify(net, skb, n, tp, block, q, parent, fh,
			       RTM_NEWTFILTER, false, rtnl_held);
		tfilter_put(tp, fh);
		/* q pointer is NULL for shared blocks */
		if (q)
			q->flags &= ~TCQ_F_CAN_BYPASS;
	}

errout:
	if (err && tp_created)
		tcf_chain_tp_delete_empty(chain, tp, rtnl_held, NULL);
errout_tp:
	if (chain) {
		if (tp && !IS_ERR(tp))
			tcf_proto_put(tp, rtnl_held, NULL);
		if (!tp_created)
			tcf_chain_put(chain);
	}
	tcf_block_release(q, block, rtnl_held);

	if (rtnl_held)
		rtnl_unlock();

	if (err == -EAGAIN) {
		/* Take rtnl lock in case EAGAIN is caused by concurrent flush
		 * of target chain.
		 */
		rtnl_held = true;
		/* Replay the request. */
		goto replay;
	}
	return err;

errout_locked:
	mutex_unlock(&chain->filter_chain_lock);
	goto errout;
}

Project: linux
File: cls_api.c

static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
			  struct netlink_ext_ack *extack)
{
	struct net *net = sock_net(skb->sk);
	struct nlattr *tca[TCA_MAX + 1];
	char name[IFNAMSIZ];
	struct tcmsg *t;
	u32 protocol;
	u32 prio;
	bool prio_allocate;
	u32 parent;
	u32 chain_index;
	struct Qdisc *q;
	struct tcf_chain_info chain_info;
	struct tcf_chain *chain;
	struct tcf_block *block;
	struct tcf_proto *tp;
	unsigned long cl;
	void *fh;
	int err;
	int tp_created;
	bool rtnl_held = false;
	u32 flags;

	if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
		return -EPERM;

replay:
	tp_created = 0;

	err = nlmsg_parse_deprecated(n, sizeof(*t), tca, TCA_MAX,
				     rtm_tca_policy, extack);
	if (err < 0)
		return err;

	t = nlmsg_data(n);
	protocol = TC_H_MIN(t->tcm_info);
	prio = TC_H_MAJ(t->tcm_info);
	prio_allocate = false;
	parent = t->tcm_parent;
	tp = NULL;
	cl = 0;
	block = NULL;
	q = NULL;
	chain = NULL;
	flags = 0;

	if (prio == 0) {
		/* If no priority is provided by the user,
		 * we allocate one.
		 */
		if (n->nlmsg_flags & NLM_F_CREATE) {
			prio = TC_H_MAKE(0x80000000U, 0U);
			prio_allocate = true;
		} else {
			NL_SET_ERR_MSG(extack, "Invalid filter command with priority of zero");
			return -ENOENT;
		}
	}

	/* Find head of filter chain. */

	err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
	if (err)
		return err;

	if (tcf_proto_check_kind(tca[TCA_KIND], name)) {
		NL_SET_ERR_MSG(extack, "Specified TC filter name too long");
		err = -EINVAL;
		goto errout;
	}

	/* Take rtnl mutex if rtnl_held was set to true on previous iteration,
	 * block is shared (no qdisc found), qdisc is not unlocked, classifier
	 * type is not specified, classifier is not unlocked.
	 */
	if (rtnl_held ||
	    (q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
	    !tcf_proto_is_unlocked(name)) {
		rtnl_held = true;
		rtnl_lock();
	}

	err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
	if (err)
		goto errout;

	block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
				 extack);
	if (IS_ERR(block)) {
		err = PTR_ERR(block);
		goto errout;
	}
	block->classid = parent;

	chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
	if (chain_index > TC_ACT_EXT_VAL_MASK) {
		NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit");
		err = -EINVAL;
		goto errout;
	}
	chain = tcf_chain_get(block, chain_index, true);
	if (!chain) {
		NL_SET_ERR_MSG(extack, "Cannot create specified filter chain");
		err = -ENOMEM;
		goto errout;
	}

	mutex_lock(&chain->filter_chain_lock);
	tp = tcf_chain_tp_find(chain, &chain_info, protocol,
			       prio, prio_allocate);
	if (IS_ERR(tp)) {
		NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
		err = PTR_ERR(tp);
		goto errout_locked;
	}

	if (tp == NULL) {
		struct tcf_proto *tp_new = NULL;

		if (chain->flushing) {
			err = -EAGAIN;
			goto errout_locked;
		}

		/* Proto-tcf does not exist, create new one */

		if (tca[TCA_KIND] == NULL || !protocol) {
			NL_SET_ERR_MSG(extack, "Filter kind and protocol must be specified");
			err = -EINVAL;
			goto errout_locked;
		}

		if (!(n->nlmsg_flags & NLM_F_CREATE)) {
			NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
			err = -ENOENT;
			goto errout_locked;
		}

		if (prio_allocate)
			prio = tcf_auto_prio(tcf_chain_tp_prev(chain,
							       &chain_info));

		mutex_unlock(&chain->filter_chain_lock);
		tp_new = tcf_proto_create(name, protocol, prio, chain,
					  rtnl_held, extack);
		if (IS_ERR(tp_new)) {
			err = PTR_ERR(tp_new);
			goto errout_tp;
		}

		tp_created = 1;
		tp = tcf_chain_tp_insert_unique(chain, tp_new, protocol, prio,
						rtnl_held);
		if (IS_ERR(tp)) {
			err = PTR_ERR(tp);
			goto errout_tp;
		}
	} else {
		mutex_unlock(&chain->filter_chain_lock);
	}

	if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
		NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
		err = -EINVAL;
		goto errout;
	}

	fh = tp->ops->get(tp, t->tcm_handle);

	if (!fh) {
		if (!(n->nlmsg_flags & NLM_F_CREATE)) {
			NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
			err = -ENOENT;
			goto errout;
		}
	} else if (n->nlmsg_flags & NLM_F_EXCL) {
		tfilter_put(tp, fh);
		NL_SET_ERR_MSG(extack, "Filter already exists");
		err = -EEXIST;
		goto errout;
	}

	if (chain->tmplt_ops && chain->tmplt_ops != tp->ops) {
		NL_SET_ERR_MSG(extack, "Chain template is set to a different filter kind");
		err = -EINVAL;
		goto errout;
	}

	if (!(n->nlmsg_flags & NLM_F_CREATE))
		flags |= TCA_ACT_FLAGS_REPLACE;
	if (!rtnl_held)
		flags |= TCA_ACT_FLAGS_NO_RTNL;
	err = tp->ops->change(net, skb, tp, cl, t->tcm_handle, tca, &fh,
			      flags, extack);
	if (err == 0) {
		tfilter_notify(net, skb, n, tp, block, q, parent, fh,
			       RTM_NEWTFILTER, false, rtnl_held);
		tfilter_put(tp, fh);
		/* q pointer is NULL for shared blocks */
		if (q)
			q->flags &= ~TCQ_F_CAN_BYPASS;
	}

errout:
	if (err && tp_created)
		tcf_chain_tp_delete_empty(chain, tp, rtnl_held, NULL);
errout_tp:
	if (chain) {
		if (tp && !IS_ERR(tp))
			tcf_proto_put(tp, rtnl_held, NULL);
		if (!tp_created)
			tcf_chain_put(chain);
	}
	tcf_block_release(q, block, rtnl_held);

	if (rtnl_held)
		rtnl_unlock();

	if (err == -EAGAIN) {
		/* Take rtnl lock in case EAGAIN is caused by concurrent flush
		 * of target chain.
		 */
		rtnl_held = true;
		/* Replay the request. */
		goto replay;
	}
	return err;

errout_locked:
	mutex_unlock(&chain->filter_chain_lock);
	goto errout;
}