Re: [syzbot] [lsm?] [net?] WARNING in kvfree_call_rcu

[Hillf Danton <hdanton@sina.com>]

> Date: Tue, 08 Jul 2025 15:27:28 -0700	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    7482bb149b9f Merge branch 'for-next/core' into for-kernelci
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=130c528c580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3c06e3e2454512b3
> dashboard link: https://syzkaller.appspot.com/bug?extid=40bf00346c3fe40f90f2
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1257428c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15fe9582580000

#syz test

--- x/net/ipv4/cipso_ipv4.c
+++ y/net/ipv4/cipso_ipv4.c
@@ -1848,6 +1848,7 @@ static int cipso_v4_get_actual_opt_len(c
  * values on failure.
  *
  */
+DEFINE_SPINLOCK(setattr_spinlock);
 int cipso_v4_sock_setattr(struct sock *sk,
 			  const struct cipso_v4_doi *doi_def,
 			  const struct netlbl_lsm_secattr *secattr,
@@ -1899,6 +1900,7 @@ int cipso_v4_sock_setattr(struct sock *s
 	kfree(buf);
 	buf = NULL;
 
+	spin_lock(&setattr_spinlock);
 	sk_inet = inet_sk(sk);
 
 	old = rcu_dereference_protected(sk_inet->inet_opt, sk_locked);
@@ -1912,6 +1914,7 @@ int cipso_v4_sock_setattr(struct sock *s
 	rcu_assign_pointer(sk_inet->inet_opt, opt);
 	if (old)
 		kfree_rcu(old, rcu);
+	spin_unlock(&setattr_spinlock);
 
 	return 0;
 
@@ -1975,10 +1978,12 @@ int cipso_v4_req_setattr(struct request_
 	kfree(buf);
 	buf = NULL;
 
+	spin_lock(&setattr_spinlock);
 	req_inet = inet_rsk(req);
 	opt = unrcu_pointer(xchg(&req_inet->ireq_opt, RCU_INITIALIZER(opt)));
 	if (opt)
 		kfree_rcu(opt, rcu);
+	spin_unlock(&setattr_spinlock);
 
 	return 0;
 
@@ -2057,9 +2062,11 @@ void cipso_v4_sock_delattr(struct sock *
 	struct inet_sock *sk_inet;
 	int hdr_delta;
 
+	spin_lock(&setattr_spinlock);
 	sk_inet = inet_sk(sk);
 
 	hdr_delta = cipso_v4_delopt(&sk_inet->inet_opt);
+	spin_unlock(&setattr_spinlock);
 	if (inet_test_bit(IS_ICSK, sk) && hdr_delta > 0) {
 		struct inet_connection_sock *sk_conn = inet_csk(sk);
 		sk_conn->icsk_ext_hdr_len -= hdr_delta;
@@ -2077,7 +2084,9 @@ void cipso_v4_sock_delattr(struct sock *
  */
 void cipso_v4_req_delattr(struct request_sock *req)
 {
+	spin_lock(&setattr_spinlock);
 	cipso_v4_delopt(&inet_rsk(req)->ireq_opt);
+	spin_unlock(&setattr_spinlock);
 }
 
 /**
--- x/include/net/sock.h
+++ y/include/net/sock.h
@@ -2922,6 +2922,7 @@ extern __u32 sysctl_rmem_max;
 
 extern __u32 sysctl_wmem_default;
 extern __u32 sysctl_rmem_default;
+extern spinlock_t setattr_spinlock;
 
 #define SKB_FRAG_PAGE_ORDER	get_order(32768)
 DECLARE_STATIC_KEY_FALSE(net_high_order_alloc_disable_key);
--- x/net/ipv4/ip_sockglue.c
+++ y/net/ipv4/ip_sockglue.c
@@ -1087,6 +1087,7 @@ int do_ip_setsockopt(struct sock *sk, in
 		err = ip_options_get(sock_net(sk), &opt, optval, optlen);
 		if (err)
 			break;
+		spin_lock(&setattr_spinlock);
 		old = rcu_dereference_protected(inet->inet_opt,
 						lockdep_sock_is_held(sk));
 		if (inet_test_bit(IS_ICSK, sk)) {
@@ -1109,6 +1110,7 @@ int do_ip_setsockopt(struct sock *sk, in
 		rcu_assign_pointer(inet->inet_opt, opt);
 		if (old)
 			kfree_rcu(old, rcu);
+		spin_unlock(&setattr_spinlock);
 		break;
 	}
 	case IP_CHECKSUM:
--