netlabel: fix RCU annotation for IPv4 options on socket creation

Xiumei reports the following splat when netlabel and TCP socket are used:

 =============================
 WARNING: suspicious RCU usage
 6.9.0-rc2+ kernel-patches#637 Not tainted
 -----------------------------
 net/ipv4/cipso_ipv4.c:1880 suspicious rcu_dereference_protected() usage!

 other info that might help us debug this:

 rcu_scheduler_active = 2, debug_locks = 1
 1 lock held by ncat/23333:
  #0: ffffffff906030c0 (rcu_read_lock){....}-{1:2}, at: netlbl_sock_setattr+0x25/0x1b0

 stack backtrace:
 CPU: 11 PID: 23333 Comm: ncat Kdump: loaded Not tainted 6.9.0-rc2+ kernel-patches#637
 Hardware name: Supermicro SYS-6027R-72RF/X9DRH-7TF/7F/iTF/iF, BIOS 3.0  07/26/2013
 Call Trace:
  <TASK>
  dump_stack_lvl+0xa9/0xc0
  lockdep_rcu_suspicious+0x117/0x190
  cipso_v4_sock_setattr+0x1ab/0x1b0
  netlbl_sock_setattr+0x13e/0x1b0
  selinux_netlbl_socket_post_create+0x3f/0x80
  selinux_socket_post_create+0x1a0/0x460
  security_socket_post_create+0x42/0x60
  __sock_create+0x342/0x3a0
  __sys_socket_create.part.22+0x42/0x70
  __sys_socket+0x37/0xb0
  __x64_sys_socket+0x16/0x20
  do_syscall_64+0x96/0x180
  ? do_user_addr_fault+0x68d/0xa30
  ? exc_page_fault+0x171/0x280
  ? asm_exc_page_fault+0x22/0x30
  entry_SYSCALL_64_after_hwframe+0x71/0x79
 RIP: 0033:0x7fbc0ca3fc1b
 Code: 73 01 c3 48 8b 0d 05 f2 1b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 29 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d d5 f1 1b 00 f7 d8 64 89 01 48
 RSP: 002b:00007fff18635208 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
 RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fbc0ca3fc1b
 RDX: 0000000000000006 RSI: 0000000000000001 RDI: 0000000000000002
 RBP: 000055d24f80f8a0 R08: 0000000000000003 R09: 0000000000000001

R10: 0000000000020000 R11: 0000000000000246 R12: 000055d24f80f8a0
 R13: 0000000000000000 R14: 000055d24f80fb88 R15: 0000000000000000
  </TASK>

The current implementation of cipso_v4_sock_setattr() replaces IP options
under the assumption that the caller holds the socket lock; however, such
assumption is not true, nor needed, in selinux_socket_post_create() hook.

Let all callers of cipso_v4_sock_setattr() specify the "socket lock held"
condition, except selinux_socket_post_create() _ where such condition can
safely be set as true even without holding the socket lock.
While at it: use rcu_replace_pointer() instead of open coding, and remove
useless NULL check of 'old' before kfree_rcu(old, ...).

v2:
 - pass lockdep_sock_is_held() through a boolean variable in the stack
   (thanks Eric Dumazet, Paul Moore, Casey Schaufler)
 - use rcu_replace_pointer() instead of rcu_dereference_protected() +
   rcu_assign_pointer()
 - remove NULL check of 'old' before kfree_rcu()

Fixes: f6d8bd0 ("inet: add RCU protection to inet->opt")
Reported-by: Xiumei Mu <[email protected]>
Signed-off-by: Davide Caratti <[email protected]>
Signed-off-by: NipaLocal <nipa@local>

Author: dcaratti

include/net/cipso_ipv4.h

@@ -183,7 +183,8 @@ int cipso_v4_getattr(const unsigned char *cipso,
 		     struct netlbl_lsm_secattr *secattr);
 int cipso_v4_sock_setattr(struct sock *sk,
 			  const struct cipso_v4_doi *doi_def,
-			  const struct netlbl_lsm_secattr *secattr);
+			  const struct netlbl_lsm_secattr *secattr,
+			  bool slock_held);
 void cipso_v4_sock_delattr(struct sock *sk);
 int cipso_v4_sock_getattr(struct sock *sk, struct netlbl_lsm_secattr *secattr);
 int cipso_v4_req_setattr(struct request_sock *req,
@@ -214,7 +215,8 @@ static inline int cipso_v4_getattr(const unsigned char *cipso,
 
 static inline int cipso_v4_sock_setattr(struct sock *sk,
 				      const struct cipso_v4_doi *doi_def,
-				      const struct netlbl_lsm_secattr *secattr)
+				      const struct netlbl_lsm_secattr *secattr,
+				      bool slock_held)
 {
 	return -ENOSYS;
 }

include/net/netlabel.h

@@ -470,7 +470,8 @@ void netlbl_bitmap_setbit(unsigned char *bitmap, u32 bit, u8 state);
 int netlbl_enabled(void);
 int netlbl_sock_setattr(struct sock *sk,
 			u16 family,
-			const struct netlbl_lsm_secattr *secattr);
+			const struct netlbl_lsm_secattr *secattr,
+			bool slock_held);
 void netlbl_sock_delattr(struct sock *sk);
 int netlbl_sock_getattr(struct sock *sk,
 			struct netlbl_lsm_secattr *secattr);
@@ -614,7 +615,8 @@ static inline int netlbl_enabled(void)
 }
 static inline int netlbl_sock_setattr(struct sock *sk,
 				      u16 family,
-				      const struct netlbl_lsm_secattr *secattr)
+				      const struct netlbl_lsm_secattr *secattr,
+				      bool slock_held)
 {
 	return -ENOSYS;
 }

net/ipv4/cipso_ipv4.c

@@ -1815,6 +1815,7 @@ static int cipso_v4_genopt(unsigned char *buf, u32 buf_len,
  * @sk: the socket
  * @doi_def: the CIPSO DOI to use
  * @secattr: the specific security attributes of the socket
+ * @slock_held: true if caller holds the socket lock
  *
  * Description:
  * Set the CIPSO option on the given socket using the DOI definition and
@@ -1826,7 +1827,8 @@ static int cipso_v4_genopt(unsigned char *buf, u32 buf_len,
  */
 int cipso_v4_sock_setattr(struct sock *sk,
 			  const struct cipso_v4_doi *doi_def,
-			  const struct netlbl_lsm_secattr *secattr)
+			  const struct netlbl_lsm_secattr *secattr,
+			  bool slock_held)
 {
 	int ret_val = -EPERM;
 	unsigned char *buf = NULL;
@@ -1876,18 +1878,15 @@ int cipso_v4_sock_setattr(struct sock *sk,
 
 	sk_inet = inet_sk(sk);
 
-	old = rcu_dereference_protected(sk_inet->inet_opt,
-					lockdep_sock_is_held(sk));
+	old = rcu_replace_pointer(sk_inet->inet_opt, opt, slock_held);
 	if (inet_test_bit(IS_ICSK, sk)) {
 		sk_conn = inet_csk(sk);
 		if (old)
 			sk_conn->icsk_ext_hdr_len -= old->opt.optlen;
-		sk_conn->icsk_ext_hdr_len += opt->opt.optlen;
+		sk_conn->icsk_ext_hdr_len += opt_len;
 		sk_conn->icsk_sync_mss(sk, sk_conn->icsk_pmtu_cookie);
 	}
-	rcu_assign_pointer(sk_inet->inet_opt, opt);
-	if (old)
-		kfree_rcu(old, rcu);
+	kfree_rcu(old, rcu);
 
 	return 0;
 

net/netlabel/netlabel_kapi.c

@@ -965,6 +965,7 @@ int netlbl_enabled(void)
  * @sk: the socket to label
  * @family: protocol family
  * @secattr: the security attributes
+ * @slock_held: true if caller holds the socket lock
  *
  * Description:
  * Attach the correct label to the given socket using the security attributes
@@ -977,7 +978,8 @@ int netlbl_enabled(void)
  */
 int netlbl_sock_setattr(struct sock *sk,
 			u16 family,
-			const struct netlbl_lsm_secattr *secattr)
+			const struct netlbl_lsm_secattr *secattr,
+			bool slock_held)
 {
 	int ret_val;
 	struct netlbl_dom_map *dom_entry;
@@ -997,7 +999,7 @@ int netlbl_sock_setattr(struct sock *sk,
 		case NETLBL_NLTYPE_CIPSOV4:
 			ret_val = cipso_v4_sock_setattr(sk,
 							dom_entry->def.cipso,
-							secattr);
+							secattr, slock_held);
 			break;
 		case NETLBL_NLTYPE_UNLABELED:
 			ret_val = 0;
@@ -1126,7 +1128,8 @@ int netlbl_conn_setattr(struct sock *sk,
 		switch (entry->type) {
 		case NETLBL_NLTYPE_CIPSOV4:
 			ret_val = cipso_v4_sock_setattr(sk,
-							entry->cipso, secattr);
+							entry->cipso, secattr,
+							lockdep_sock_is_held(sk));
 			break;
 		case NETLBL_NLTYPE_UNLABELED:
 			/* just delete the protocols we support for right now

security/selinux/netlabel.c

@@ -402,7 +402,10 @@ int selinux_netlbl_socket_post_create(struct sock *sk, u16 family)
 	secattr = selinux_netlbl_sock_genattr(sk);
 	if (secattr == NULL)
 		return -ENOMEM;
-	rc = netlbl_sock_setattr(sk, family, secattr);
+	/* On socket creation, replacement of IP options is safe even if
+	 * the caller does not hold the socket lock.
+	 */
+	rc = netlbl_sock_setattr(sk, family, secattr, true);
 	switch (rc) {
 	case 0:
 		sksec->nlbl_state = NLBL_LABELED;

security/smack/smack_lsm.c

@@ -2565,7 +2565,8 @@ static int smack_netlbl_add(struct sock *sk)
 	local_bh_disable();
 	bh_lock_sock_nested(sk);
 
-	rc = netlbl_sock_setattr(sk, sk->sk_family, &skp->smk_netlabel);
+	rc = netlbl_sock_setattr(sk, sk->sk_family, &skp->smk_netlabel,
+				 lockdep_sock_is_held(sk));
 	switch (rc) {
 	case 0:
 		ssp->smk_state = SMK_NETLBL_LABELED;