On Mon, Mar 10, 2025 at 8:03 PM Edward Adam Davis <eadavis@xxxxxx> wrote: > > 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. > > Use READ_ONCE/WRITE_ONCE 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> > --- > V1 -> V2: replace with READ_ONCE/WRITE_ONCE Thanks for the patch. Did you audit all other users of sksec->sid to see if they too should be wrapped with READ_ONCE()/WRITE_ONCE() or are already safe? > > security/selinux/hooks.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 7b867dfec88b..77d2953eaa4d 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -4678,7 +4678,7 @@ static int selinux_socket_post_create(struct socket *sock, int family, > if (sock->sk) { > sksec = selinux_sock(sock->sk); > sksec->sclass = sclass; > - sksec->sid = sid; > + WRITE_ONCE(sksec->sid, sid); > /* Allows detection of the first association on this socket */ > if (sksec->sclass == SECCLASS_SCTP_SOCKET) > sksec->sctp_assoc_state = SCTP_ASSOC_UNSET; > @@ -5126,7 +5126,7 @@ 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 = READ_ONCE(sksec->sid); > struct common_audit_data ad; > struct lsm_network_audit net; > char *addrp; > -- > 2.43.0 >
