linux-kernel - [PATCH] selinux: read and write sid under lock

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Message-ID: <tencent_0BEE86CD3878D26D402DDD6F949484E96E0A@qq.com>
Date: Sun,  9 Mar 2025 12:55:02 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+00c633585760c05507c3@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	omosnace@...hat.com,
	paul@...l-moore.com,
	selinux@...r.kernel.org,
	stephen.smalley.work@...il.com,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH] selinux: read and write sid under lock

syzbot reported a data-race in selinux_socket_post_create /
selinux_socket_sock_rcv_skb. [1]

When creating the socket path and receiving the network data packet path,
effective data access protection is not performed when reading and writing
the sid, resulting in a race condition.

Add a lock to synchronize the two.

[1]
BUG: KCSAN: data-race in selinux_socket_post_create / selinux_socket_sock_rcv_skb

write to 0xffff88811b989e30 of 4 bytes by task 3803 on cpu 0:
 selinux_socket_post_create+0x1b5/0x2a0 security/selinux/hooks.c:4681
 security_socket_post_create+0x5b/0xa0 security/security.c:4577
 __sock_create+0x35b/0x5a0 net/socket.c:1571
 sock_create net/socket.c:1606 [inline]
 __sys_socket_create net/socket.c:1643 [inline]
 __sys_socket+0xae/0x240 net/socket.c:1690
 __do_sys_socket net/socket.c:1704 [inline]
 __se_sys_socket net/socket.c:1702 [inline]
 __x64_sys_socket+0x3f/0x50 net/socket.c:1702
 x64_sys_call+0x2cf2/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:42
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b989e30 of 4 bytes by task 3805 on cpu 1:
 selinux_socket_sock_rcv_skb+0x72/0x6a0 security/selinux/hooks.c:5129
 security_sock_rcv_skb+0x3d/0x80 security/security.c:4781
 sk_filter_trim_cap+0xca/0x3c0 net/core/filter.c:151
 sk_filter include/linux/filter.h:1062 [inline]
 sock_queue_rcv_skb_reason+0x28/0xc0 net/core/sock.c:527
 sock_queue_rcv_skb include/net/sock.h:2403 [inline]
 packet_rcv_spkt+0x2f7/0x3b0 net/packet/af_packet.c:1967
 deliver_skb net/core/dev.c:2449 [inline]
 __netif_receive_skb_core+0x48f/0x2350 net/core/dev.c:5737
 __netif_receive_skb_list_core+0x115/0x520 net/core/dev.c:5968
 __netif_receive_skb_list net/core/dev.c:6035 [inline]
 netif_receive_skb_list_internal+0x4e4/0x660 net/core/dev.c:6126
 netif_receive_skb_list+0x31/0x230 net/core/dev.c:6178
 xdp_recv_frames net/bpf/test_run.c:280 [inline]
 xdp_test_run_batch net/bpf/test_run.c:361 [inline]
 bpf_test_run_xdp_live+0xe10/0x1040 net/bpf/test_run.c:390
 bpf_prog_test_run_xdp+0x51d/0x8b0 net/bpf/test_run.c:1316
 bpf_prog_test_run+0x20f/0x3a0 kernel/bpf/syscall.c:4407
 __sys_bpf+0x400/0x7a0 kernel/bpf/syscall.c:5813
 __do_sys_bpf kernel/bpf/syscall.c:5902 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5900 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5900
 x64_sys_call+0x2914/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000003 -> 0x00000087

Reported-by: syzbot+00c633585760c05507c3@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=00c633585760c05507c3
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 security/selinux/hooks.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 7b867dfec88b..ea5d0273f9d5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4677,8 +4677,10 @@ static int selinux_socket_post_create(struct socket *sock, int family,
 
 	if (sock->sk) {
 		sksec = selinux_sock(sock->sk);
+		spin_lock(&sksec->lock);
 		sksec->sclass = sclass;
 		sksec->sid = sid;
+		spin_unlock(&sksec->lock);
 		/* Allows detection of the first association on this socket */
 		if (sksec->sclass == SECCLASS_SCTP_SOCKET)
 			sksec->sctp_assoc_state = SCTP_ASSOC_UNSET;
@@ -5126,7 +5128,7 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	int err, peerlbl_active, secmark_active;
 	struct sk_security_struct *sksec = selinux_sock(sk);
 	u16 family = sk->sk_family;
-	u32 sk_sid = sksec->sid;
+	u32 sk_sid;
 	struct common_audit_data ad;
 	struct lsm_network_audit net;
 	char *addrp;
@@ -5155,6 +5157,9 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	if (err)
 		return err;
 
+	spin_lock(&sksec->lock);
+	sk_sid = sksec->sid;
+	spin_unlock(&sksec->lock);
 	if (peerlbl_active) {
 		u32 peer_sid;
 
-- 
2.43.0