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

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Message-ID: <20250711130450.3505-1-hdanton@sina.com>
Date: Fri, 11 Jul 2025 21:04:48 +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/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;
 
@@ -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;
 
@@ -1998,13 +2003,19 @@ req_setattr_failure:
  * values on failure.
  *
  */
-static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
+static int cipso_v4_delopt(struct sock *sk)
 {
-	struct ip_options_rcu *opt = rcu_dereference_protected(*opt_ptr, 1);
+	struct ip_options_rcu *opt;
+	struct inet_sock *sk_inet;
 	int hdr_delta = 0;
 
-	if (!opt || opt->opt.cipso == 0)
+	spin_lock(&setattr_spinlock);
+	sk_inet = inet_sk(sk);
+	opt = rcu_dereference_protected(sk_inet->inet_opt, 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;
@@ -2036,10 +2047,11 @@ static int cipso_v4_delopt(struct ip_opt
 	} else {
 		/* only the cipso option was present on the socket so we can
 		 * remove the entire option struct */
-		*opt_ptr = NULL;
+		rcu_assign_pointer(sk_inet->inet_opt, NULL);
 		hdr_delta = opt->opt.optlen;
 		kfree_rcu(opt, rcu);
 	}
+	spin_unlock(&setattr_spinlock);
 
 	return hdr_delta;
 }
@@ -2054,12 +2066,9 @@ static int cipso_v4_delopt(struct ip_opt
  */
 void cipso_v4_sock_delattr(struct sock *sk)
 {
-	struct inet_sock *sk_inet;
 	int hdr_delta;
 
-	sk_inet = inet_sk(sk);
-
-	hdr_delta = cipso_v4_delopt(&sk_inet->inet_opt);
+	hdr_delta = cipso_v4_delopt(sk);
 	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 +2086,7 @@ void cipso_v4_sock_delattr(struct sock *
  */
 void cipso_v4_req_delattr(struct request_sock *req)
 {
-	cipso_v4_delopt(&inet_rsk(req)->ireq_opt);
+	cipso_v4_delopt(req_to_sk(req));
 }
 
 /**
--