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.
  *
  */
+static 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;
 
@@ -1976,9 +1979,11 @@ int cipso_v4_req_setattr(struct request_
 	buf = NULL;
 
 	req_inet = inet_rsk(req);
+	spin_lock(&setattr_spinlock);
 	opt = unrcu_pointer(xchg(&req_inet->ireq_opt, RCU_INITIALIZER(opt)));
 	if (opt)
 		kfree_rcu(opt, rcu);
+	spin_unlock(&setattr_spinlock);
 
 	return 0;
 
@@ -2000,11 +2005,15 @@ req_setattr_failure:
  */
 static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
 {
-	struct ip_options_rcu *opt = rcu_dereference_protected(*opt_ptr, 1);
+	struct ip_options_rcu *opt;
 	int hdr_delta = 0;
 
-	if (!opt || opt->opt.cipso == 0)
+	spin_lock(&setattr_spinlock);
+	opt = rcu_dereference_protected(*opt_ptr, 1);
+	if (!opt || opt->opt.cipso == 0) {
+		spin_unlock(&setattr_spinlock);
 		return 0;
+	}
 	if (opt->opt.srr || opt->opt.rr || opt->opt.ts || opt->opt.router_alert) {
 		u8 cipso_len;
 		u8 cipso_off;
@@ -2040,6 +2049,7 @@ static int cipso_v4_delopt(struct ip_opt
 		hdr_delta = opt->opt.optlen;
 		kfree_rcu(opt, rcu);
 	}
+	spin_unlock(&setattr_spinlock);
 
 	return hdr_delta;
 }
--