raw: Fix NULL deref in raw_get_next().

Dae R. Jeong reported a NULL deref in raw_get_next() [0].

It seems that the repro was running these sequences in parallel so
that one thread was iterating on a socket that was being freed in
another netns.

unshare(0x40060200)
r0 = syz_open_procfs(0x0, &(0x7f0000002080)='net/raw\x00')
socket$inet_icmp_raw(0x2, 0x3, 0x1)
pread64(r0, &(0x7f0000000000)=""/10, 0xa, 0x10000000007f)

After commit 0daf07e52709 ("raw: convert raw sockets to RCU"), we
use RCU and hlist_nulls_for_each_entry() to iterate over SOCK_RAW
sockets. However, we should use spinlock for slow paths to avoid
the NULL deref.

Also, SOCK_RAW does not use SLAB_TYPESAFE_BY_RCU, and the slab object
is not reused during iteration in the grace period. In fact, the
lockless readers do not check the nulls marker with get_nulls_value().
So, SOCK_RAW should use hlist instead of hlist_nulls.

Instead of adding an unnecessary barrier by sk_nulls_for_each_rcu(),
let's convert hlist_nulls to hlist and use sk_for_each_rcu() for
fast paths and sk_for_each() and spinlock for /proc/net/raw.

[0]:
general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
CPU: 2 PID: 20952 Comm: syz-executor.0 Not tainted 6.2.0-g048ec869bafd-dirty #7
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
RIP: 0010:read_pnet include/net/net_namespace.h:383 [inline]
RIP: 0010:sock_net include/net/sock.h:649 [inline]
RIP: 0010:raw_get_next net/ipv4/raw.c:974 [inline]
RIP: 0010:raw_get_idx net/ipv4/raw.c:986 [inline]
RIP: 0010:raw_seq_start+0x431/0x800 net/ipv4/raw.c:995
Code: ef e8 33 3d 94 f7 49 8b 6d 00 4c 89 ef e8 b7 65 5f f7 49 89 ed 49 83 c5 98 0f 84 9a 00 00 00 48 83 c5 c8 48 89 e8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 ef e8 00 3d 94 f7 4c 8b 7d 00 48 89 ef
RSP: 0018:ffffc9001154f9b0 EFLAGS: 00010206
RAX: 0000000000000005 RBX: 1ffff1100302c8fd RCX: 0000000000000000
RDX: 0000000000000028 RSI: ffffc9001154f988 RDI: ffffc9000f77a338
RBP: 0000000000000029 R08: ffffffff8a50ffb4 R09: fffffbfff24b6bd9
R10: fffffbfff24b6bd9 R11: 0000000000000000 R12: ffff88801db73b78
R13: fffffffffffffff9 R14: dffffc0000000000 R15: 0000000000000030
FS: 00007f843ae8e700(0000) GS:ffff888063700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055bb9614b35f CR3: 000000003c672000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
seq_read_iter+0x4c6/0x10f0 fs/seq_file.c:225
seq_read+0x224/0x320 fs/seq_file.c:162
pde_read fs/proc/inode.c:316 [inline]
proc_reg_read+0x23f/0x330 fs/proc/inode.c:328
vfs_read+0x31e/0xd30 fs/read_write.c:468
ksys_pread64 fs/read_write.c:665 [inline]
__do_sys_pread64 fs/read_write.c:675 [inline]
__se_sys_pread64 fs/read_write.c:672 [inline]
__x64_sys_pread64+0x1e9/0x280 fs/read_write.c:672
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4e/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x478d29
Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f843ae8dbe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000011
RAX: ffffffffffffffda RBX: 0000000000791408 RCX: 0000000000478d29
RDX: 000000000000000a RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000f477909a R08: 0000000000000000 R09: 0000000000000000
R10: 000010000000007f R11: 0000000000000246 R12: 0000000000791740
R13: 0000000000791414 R14: 0000000000791408 R15: 00007ffc2eb48a50
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:read_pnet include/net/net_namespace.h:383 [inline]
RIP: 0010:sock_net include/net/sock.h:649 [inline]
RIP: 0010:raw_get_next net/ipv4/raw.c:974 [inline]
RIP: 0010:raw_get_idx net/ipv4/raw.c:986 [inline]
RIP: 0010:raw_seq_start+0x431/0x800 net/ipv4/raw.c:995
Code: ef e8 33 3d 94 f7 49 8b 6d 00 4c 89 ef e8 b7 65 5f f7 49 89 ed 49 83 c5 98 0f 84 9a 00 00 00 48 83 c5 c8 48 89 e8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 ef e8 00 3d 94 f7 4c 8b 7d 00 48 89 ef
RSP: 0018:ffffc9001154f9b0 EFLAGS: 00010206
RAX: 0000000000000005 RBX: 1ffff1100302c8fd RCX: 0000000000000000
RDX: 0000000000000028 RSI: ffffc9001154f988 RDI: ffffc9000f77a338
RBP: 0000000000000029 R08: ffffffff8a50ffb4 R09: fffffbfff24b6bd9
R10: fffffbfff24b6bd9 R11: 0000000000000000 R12: ffff88801db73b78
R13: fffffffffffffff9 R14: dffffc0000000000 R15: 0000000000000030
FS: 00007f843ae8e700(0000) GS:ffff888063700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f92ff166000 CR3: 000000003c672000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Fixes: 0daf07e52709 ("raw: convert raw sockets to RCU")
Reported-by: syzbot <[e-mail]>
Reported-by: Dae R. Jeong <[e-mail]>
Link: https://lore.kernel.org/netdev/ZCA2mGV_cmq7lIfV@dragonet/
Signed-off-by: Kuniyuki Iwashima <[e-mail]>
Reviewed-by: Eric Dumazet <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/raw.h

···
 struct raw_hashinfo {
 	spinlock_t lock;
 
-	struct hlist_nulls_head ht[RAW_HTABLE_SIZE] ____cacheline_aligned;
+	struct hlist_head ht[RAW_HTABLE_SIZE] ____cacheline_aligned;
 };
 
 static inline u32 raw_hashfunc(const struct net *net, u32 proto)
···
 
 	spin_lock_init(&hashinfo->lock);
 	for (i = 0; i < RAW_HTABLE_SIZE; i++)
-		INIT_HLIST_NULLS_HEAD(&hashinfo->ht[i], i);
+		INIT_HLIST_HEAD(&hashinfo->ht[i]);
 }
 
 #ifdef CONFIG_PROC_FS

net/ipv4/raw.c

···
 int raw_hash_sk(struct sock *sk)
 {
 	struct raw_hashinfo *h = sk->sk_prot->h.raw_hash;
-	struct hlist_nulls_head *hlist;
+	struct hlist_head *hlist;
 
 	hlist = &h->ht[raw_hashfunc(sock_net(sk), inet_sk(sk)->inet_num)];
 
 	spin_lock(&h->lock);
-	__sk_nulls_add_node_rcu(sk, hlist);
+	sk_add_node_rcu(sk, hlist);
 	sock_set_flag(sk, SOCK_RCU_FREE);
 	spin_unlock(&h->lock);
 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
···
 	struct raw_hashinfo *h = sk->sk_prot->h.raw_hash;
 
 	spin_lock(&h->lock);
-	if (__sk_nulls_del_node_init_rcu(sk))
+	if (sk_del_node_init_rcu(sk))
 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 	spin_unlock(&h->lock);
 }
···
 static int raw_v4_input(struct net *net, struct sk_buff *skb,
 			const struct iphdr *iph, int hash)
 {
-	struct hlist_nulls_head *hlist;
-	struct hlist_nulls_node *hnode;
 	int sdif = inet_sdif(skb);
+	struct hlist_head *hlist;
 	int dif = inet_iif(skb);
 	int delivered = 0;
 	struct sock *sk;
 
 	hlist = &raw_v4_hashinfo.ht[hash];
 	rcu_read_lock();
-	sk_nulls_for_each(sk, hnode, hlist) {
+	sk_for_each_rcu(sk, hlist) {
 		if (!raw_v4_match(net, sk, iph->protocol,
 				  iph->saddr, iph->daddr, dif, sdif))
 			continue;
···
 void raw_icmp_error(struct sk_buff *skb, int protocol, u32 info)
 {
 	struct net *net = dev_net(skb->dev);
-	struct hlist_nulls_head *hlist;
-	struct hlist_nulls_node *hnode;
 	int dif = skb->dev->ifindex;
 	int sdif = inet_sdif(skb);
+	struct hlist_head *hlist;
 	const struct iphdr *iph;
 	struct sock *sk;
 	int hash;
···
 	hlist = &raw_v4_hashinfo.ht[hash];
 
 	rcu_read_lock();
-	sk_nulls_for_each(sk, hnode, hlist) {
+	sk_for_each_rcu(sk, hlist) {
 		iph = (const struct iphdr *)skb->data;
 		if (!raw_v4_match(net, sk, iph->protocol,
 				  iph->daddr, iph->saddr, dif, sdif))
···
 {
 	struct raw_hashinfo *h = pde_data(file_inode(seq->file));
 	struct raw_iter_state *state = raw_seq_private(seq);
-	struct hlist_nulls_head *hlist;
-	struct hlist_nulls_node *hnode;
+	struct hlist_head *hlist;
 	struct sock *sk;
 
 	for (state->bucket = bucket; state->bucket < RAW_HTABLE_SIZE;
 			++state->bucket) {
 		hlist = &h->ht[state->bucket];
-		sk_nulls_for_each(sk, hnode, hlist) {
+		sk_for_each(sk, hlist) {
 			if (sock_net(sk) == seq_file_net(seq))
 				return sk;
 		}
···
 	struct raw_iter_state *state = raw_seq_private(seq);
 
 	do {
-		sk = sk_nulls_next(sk);
+		sk = sk_next(sk);
 	} while (sk && sock_net(sk) != seq_file_net(seq));
 
 	if (!sk)
···
 }
 
 void *raw_seq_start(struct seq_file *seq, loff_t *pos)
-	__acquires(RCU)
+	__acquires(&h->lock)
 {
-	rcu_read_lock();
+	struct raw_hashinfo *h = pde_data(file_inode(seq->file));
+
+	spin_lock(&h->lock);
+
 	return *pos ? raw_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
 }
 EXPORT_SYMBOL_GPL(raw_seq_start);
···
 EXPORT_SYMBOL_GPL(raw_seq_next);
 
 void raw_seq_stop(struct seq_file *seq, void *v)
-	__releases(RCU)
+	__releases(&h->lock)
 {
-	rcu_read_unlock();
+	struct raw_hashinfo *h = pde_data(file_inode(seq->file));
+
+	spin_unlock(&h->lock);
 }
 EXPORT_SYMBOL_GPL(raw_seq_stop);
 

net/ipv4/raw_diag.c

···
 static struct sock *raw_sock_get(struct net *net, const struct inet_diag_req_v2 *r)
 {
 	struct raw_hashinfo *hashinfo = raw_get_hashinfo(r);
-	struct hlist_nulls_head *hlist;
-	struct hlist_nulls_node *hnode;
+	struct hlist_head *hlist;
 	struct sock *sk;
 	int slot;
 
···
 	rcu_read_lock();
 	for (slot = 0; slot < RAW_HTABLE_SIZE; slot++) {
 		hlist = &hashinfo->ht[slot];
-		sk_nulls_for_each(sk, hnode, hlist) {
+		sk_for_each_rcu(sk, hlist) {
 			if (raw_lookup(net, sk, r)) {
 				/*
 				 * Grab it and keep until we fill
···
 	struct raw_hashinfo *hashinfo = raw_get_hashinfo(r);
 	struct net *net = sock_net(skb->sk);
 	struct inet_diag_dump_data *cb_data;
-	struct hlist_nulls_head *hlist;
-	struct hlist_nulls_node *hnode;
 	int num, s_num, slot, s_slot;
+	struct hlist_head *hlist;
 	struct sock *sk = NULL;
 	struct nlattr *bc;
 
···
 		num = 0;
 
 		hlist = &hashinfo->ht[slot];
-		sk_nulls_for_each(sk, hnode, hlist) {
+		sk_for_each_rcu(sk, hlist) {
 			struct inet_sock *inet = inet_sk(sk);
 
 			if (!net_eq(sock_net(sk), net))

net/ipv6/raw.c

···
 static bool ipv6_raw_deliver(struct sk_buff *skb, int nexthdr)
 {
 	struct net *net = dev_net(skb->dev);
-	struct hlist_nulls_head *hlist;
-	struct hlist_nulls_node *hnode;
 	const struct in6_addr *saddr;
 	const struct in6_addr *daddr;
+	struct hlist_head *hlist;
 	struct sock *sk;
 	bool delivered = false;
 	__u8 hash;
···
 	hash = raw_hashfunc(net, nexthdr);
 	hlist = &raw_v6_hashinfo.ht[hash];
 	rcu_read_lock();
-	sk_nulls_for_each(sk, hnode, hlist) {
+	sk_for_each_rcu(sk, hlist) {
 		int filtered;
 
 		if (!raw_v6_match(net, sk, nexthdr, daddr, saddr,
···
 		u8 type, u8 code, int inner_offset, __be32 info)
 {
 	struct net *net = dev_net(skb->dev);
-	struct hlist_nulls_head *hlist;
-	struct hlist_nulls_node *hnode;
+	struct hlist_head *hlist;
 	struct sock *sk;
 	int hash;
 
 	hash = raw_hashfunc(net, nexthdr);
 	hlist = &raw_v6_hashinfo.ht[hash];
 	rcu_read_lock();
-	sk_nulls_for_each(sk, hnode, hlist) {
+	sk_for_each_rcu(sk, hlist) {
 		/* Note: ipv6_hdr(skb) != skb->data */
 		const struct ipv6hdr *ip6h = (const struct ipv6hdr *)skb->data;