linux-kernel - Re: [syzbot] [lsm?] [net?] WARNING in kvfree_call

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Message-ID: <20250713051026.3829-1-hdanton@sina.com>
Date: Sun, 13 Jul 2025 13:10:25 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+40bf00346c3fe40f90f2@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [lsm?] [net?] WARNING in kvfree_call_rcu

> 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/include/net/inet_sock.h
+++ y/include/net/inet_sock.h
@@ -227,6 +227,7 @@ struct inet_sock {
 	__be16			inet_sport;
 	struct ip_options_rcu __rcu	*inet_opt;
 	atomic_t		inet_id;
+	spinlock_t		inet_lock;
 
 	__u8			tos;
 	__u8			min_ttl;
--- x/net/ipv4/af_inet.c
+++ y/net/ipv4/af_inet.c
@@ -351,6 +351,7 @@ lookup_protocol:
 		inet->pmtudisc = IP_PMTUDISC_WANT;
 
 	atomic_set(&inet->inet_id, 0);
+	spin_lock_init(&inet->inet_lock);
 
 	sock_init_data(sock, sk);
 
--- 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(&inet->inet_lock);
 		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(&inet->inet_lock);
 		break;
 	}
 	case IP_CHECKSUM:
--- x/net/ipv4/cipso_ipv4.c
+++ y/net/ipv4/cipso_ipv4.c
@@ -1900,6 +1900,7 @@ int cipso_v4_sock_setattr(struct sock *s
 	buf = NULL;
 
 	sk_inet = inet_sk(sk);
+	spin_lock(&sk_inet->inet_lock);
 
 	old = rcu_dereference_protected(sk_inet->inet_opt, sk_locked);
 	if (inet_test_bit(IS_ICSK, sk)) {
@@ -1912,6 +1913,7 @@ int cipso_v4_sock_setattr(struct sock *s
 	rcu_assign_pointer(sk_inet->inet_opt, opt);
 	if (old)
 		kfree_rcu(old, rcu);
+	spin_unlock(&sk_inet->inet_lock);
 
 	return 0;
 
@@ -2059,7 +2061,9 @@ void cipso_v4_sock_delattr(struct sock *
 
 	sk_inet = inet_sk(sk);
 
+	spin_lock(&sk_inet->inet_lock);
 	hdr_delta = cipso_v4_delopt(&sk_inet->inet_opt);
+	spin_unlock(&sk_inet->inet_lock);
 	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;
--