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@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=00c633585760c05507c3 Signed-off-by: Edward Adam Davis <eadavis@xxxxxx> --- 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
