x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 304 insertions, 0 deletions

diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
new file mode 100644
index 000000000..6e90d0bf9
--- /dev/null
+++ b/net/ipv6/ping.c
@@ -0,0 +1,304 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		"Ping" sockets
+ *
+ * Based on ipv4/ping.c code.
+ *
+ * Authors:	Lorenzo Colitti (IPv6 support)
+ *		Vasiliy Kulikov / Openwall (IPv4 implementation, for Linux 2.6),
+ *		Pavel Kankovsky (IPv4 implementation, for Linux 2.4.32)
+ */
+
+#include <net/addrconf.h>
+#include <net/ipv6.h>
+#include <net/ip6_route.h>
+#include <net/protocol.h>
+#include <net/udp.h>
+#include <net/transp_v6.h>
+#include <linux/proc_fs.h>
+#include <linux/bpf-cgroup.h>
+#include <net/ping.h>
+
+/* Compatibility glue so we can support IPv6 when it's compiled as a module */
+static int dummy_ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len)
+{
+	return -EAFNOSUPPORT;
+}
+static void dummy_ip6_datagram_recv_ctl(struct sock *sk, struct msghdr *msg,
+				       struct sk_buff *skb)
+{
+}
+static int dummy_icmpv6_err_convert(u8 type, u8 code, int *err)
+{
+	return -EAFNOSUPPORT;
+}
+static void dummy_ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
+				  __be16 port, u32 info, u8 *payload) {}
+static int dummy_ipv6_chk_addr(struct net *net, const struct in6_addr *addr,
+			       const struct net_device *dev, int strict)
+{
+	return 0;
+}
+
+static int ping_v6_pre_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
+			       int addr_len)
+{
+	/* This check is replicated from __ip6_datagram_connect() and
+	 * intended to prevent BPF program called below from accessing
+	 * bytes that are out of the bound specified by user in addr_len.
+	 */
+
+	if (addr_len < SIN6_LEN_RFC2133)
+		return -EINVAL;
+
+	return BPF_CGROUP_RUN_PROG_INET6_CONNECT_LOCK(sk, uaddr, &addr_len);
+}
+
+static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct ipv6_pinfo *np = inet6_sk(sk);
+	struct icmp6hdr user_icmph;
+	int addr_type;
+	struct in6_addr *daddr;
+	int oif = 0;
+	struct flowi6 fl6;
+	int err;
+	struct dst_entry *dst;
+	struct rt6_info *rt;
+	struct pingfakehdr pfh;
+	struct ipcm6_cookie ipc6;
+
+	err = ping_common_sendmsg(AF_INET6, msg, len, &user_icmph,
+				  sizeof(user_icmph));
+	if (err)
+		return err;
+
+	memset(&fl6, 0, sizeof(fl6));
+
+	if (msg->msg_name) {
+		DECLARE_SOCKADDR(struct sockaddr_in6 *, u, msg->msg_name);
+		if (msg->msg_namelen < sizeof(*u))
+			return -EINVAL;
+		if (u->sin6_family != AF_INET6) {
+			return -EAFNOSUPPORT;
+		}
+		daddr = &(u->sin6_addr);
+		if (inet6_test_bit(SNDFLOW, sk))
+			fl6.flowlabel = u->sin6_flowinfo & IPV6_FLOWINFO_MASK;
+		if (__ipv6_addr_needs_scope_id(ipv6_addr_type(daddr)))
+			oif = u->sin6_scope_id;
+	} else {
+		if (sk->sk_state != TCP_ESTABLISHED)
+			return -EDESTADDRREQ;
+		daddr = &sk->sk_v6_daddr;
+		fl6.flowlabel = np->flow_label;
+	}
+
+	if (!oif)
+		oif = sk->sk_bound_dev_if;
+
+	if (!oif)
+		oif = np->sticky_pktinfo.ipi6_ifindex;
+
+	if (!oif && ipv6_addr_is_multicast(daddr))
+		oif = READ_ONCE(np->mcast_oif);
+	else if (!oif)
+		oif = READ_ONCE(np->ucast_oif);
+
+	addr_type = ipv6_addr_type(daddr);
+	if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) ||
+	    (addr_type & IPV6_ADDR_MAPPED) ||
+	    (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if &&
+	     l3mdev_master_ifindex_by_index(sock_net(sk), oif) != sk->sk_bound_dev_if))
+		return -EINVAL;
+
+	ipcm6_init_sk(&ipc6, sk);
+
+	fl6.flowi6_oif = oif;
+
+	if (msg->msg_controllen) {
+		struct ipv6_txoptions opt = {};
+
+		opt.tot_len = sizeof(opt);
+		ipc6.opt = &opt;
+
+		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6);
+		if (err < 0)
+			return err;
+
+		/* Changes to txoptions and flow info are not implemented, yet.
+		 * Drop the options.
+		 */
+		ipc6.opt = NULL;
+	}
+
+	fl6.flowi6_proto = IPPROTO_ICMPV6;
+	fl6.saddr = np->saddr;
+	fl6.daddr = *daddr;
+	fl6.flowi6_mark = ipc6.sockc.mark;
+	fl6.flowi6_uid = sk_uid(sk);
+	fl6.fl6_icmp_type = user_icmph.icmp6_type;
+	fl6.fl6_icmp_code = user_icmph.icmp6_code;
+	security_sk_classify_flow(sk, flowi6_to_flowi_common(&fl6));
+
+	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);
+
+	dst = ip6_sk_dst_lookup_flow(sk, &fl6, daddr, false);
+	if (IS_ERR(dst))
+		return PTR_ERR(dst);
+	rt = dst_rt6_info(dst);
+
+	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
+		fl6.flowi6_oif = READ_ONCE(np->mcast_oif);
+	else if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = READ_ONCE(np->ucast_oif);
+
+	pfh.icmph.type = user_icmph.icmp6_type;
+	pfh.icmph.code = user_icmph.icmp6_code;
+	pfh.icmph.checksum = 0;
+	pfh.icmph.un.echo.id = inet->inet_sport;
+	pfh.icmph.un.echo.sequence = user_icmph.icmp6_sequence;
+	pfh.msg = msg;
+	pfh.wcheck = 0;
+	pfh.family = AF_INET6;
+
+	if (ipc6.hlimit < 0)
+		ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);
+
+	lock_sock(sk);
+	err = ip6_append_data(sk, ping_getfrag, &pfh, len,
+			      sizeof(struct icmp6hdr), &ipc6, &fl6, rt,
+			      MSG_DONTWAIT);
+
+	if (err) {
+		ICMP6_INC_STATS(sock_net(sk), rt->rt6i_idev,
+				ICMP6_MIB_OUTERRORS);
+		ip6_flush_pending_frames(sk);
+	} else {
+		icmpv6_push_pending_frames(sk, &fl6,
+					   (struct icmp6hdr *)&pfh.icmph, len);
+	}
+	release_sock(sk);
+
+	dst_release(dst);
+
+	if (err)
+		return err;
+
+	return len;
+}
+
+struct proto pingv6_prot = {
+	.name =		"PINGv6",
+	.owner =	THIS_MODULE,
+	.init =		ping_init_sock,
+	.close =	ping_close,
+	.pre_connect =	ping_v6_pre_connect,
+	.connect =	ip6_datagram_connect_v6_only,
+	.disconnect =	__udp_disconnect,
+	.setsockopt =	ipv6_setsockopt,
+	.getsockopt =	ipv6_getsockopt,
+	.sendmsg =	ping_v6_sendmsg,
+	.recvmsg =	ping_recvmsg,
+	.bind =		ping_bind,
+	.backlog_rcv =	ping_queue_rcv_skb,
+	.unhash =	ping_unhash,
+	.get_port =	ping_get_port,
+	.put_port =	ping_unhash,
+	.obj_size =	sizeof(struct raw6_sock),
+	.ipv6_pinfo_offset = offsetof(struct raw6_sock, inet6),
+};
+EXPORT_SYMBOL_GPL(pingv6_prot);
+
+static struct inet_protosw pingv6_protosw = {
+	.type =      SOCK_DGRAM,
+	.protocol =  IPPROTO_ICMPV6,
+	.prot =      &pingv6_prot,
+	.ops =       &inet6_sockraw_ops,
+	.flags =     INET_PROTOSW_REUSE,
+};
+
+#ifdef CONFIG_PROC_FS
+static void *ping_v6_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	return ping_seq_start(seq, pos, AF_INET6);
+}
+
+static int ping_v6_seq_show(struct seq_file *seq, void *v)
+{
+	if (v == SEQ_START_TOKEN) {
+		seq_puts(seq, IPV6_SEQ_DGRAM_HEADER);
+	} else {
+		int bucket = ((struct ping_iter_state *) seq->private)->bucket;
+		struct inet_sock *inet = inet_sk((struct sock *)v);
+		__u16 srcp = ntohs(inet->inet_sport);
+		__u16 destp = ntohs(inet->inet_dport);
+		ip6_dgram_sock_seq_show(seq, v, srcp, destp, bucket);
+	}
+	return 0;
+}
+
+static const struct seq_operations ping_v6_seq_ops = {
+	.start		= ping_v6_seq_start,
+	.show		= ping_v6_seq_show,
+	.next		= ping_seq_next,
+	.stop		= ping_seq_stop,
+};
+
+static int __net_init ping_v6_proc_init_net(struct net *net)
+{
+	if (!proc_create_net("icmp6", 0444, net->proc_net, &ping_v6_seq_ops,
+			sizeof(struct ping_iter_state)))
+		return -ENOMEM;
+	return 0;
+}
+
+static void __net_exit ping_v6_proc_exit_net(struct net *net)
+{
+	remove_proc_entry("icmp6", net->proc_net);
+}
+
+static struct pernet_operations ping_v6_net_ops = {
+	.init = ping_v6_proc_init_net,
+	.exit = ping_v6_proc_exit_net,
+};
+#endif
+
+int __init pingv6_init(void)
+{
+#ifdef CONFIG_PROC_FS
+	int ret = register_pernet_subsys(&ping_v6_net_ops);
+	if (ret)
+		return ret;
+#endif
+	pingv6_ops.ipv6_recv_error = ipv6_recv_error;
+	pingv6_ops.ip6_datagram_recv_common_ctl = ip6_datagram_recv_common_ctl;
+	pingv6_ops.ip6_datagram_recv_specific_ctl =
+		ip6_datagram_recv_specific_ctl;
+	pingv6_ops.icmpv6_err_convert = icmpv6_err_convert;
+	pingv6_ops.ipv6_icmp_error = ipv6_icmp_error;
+	pingv6_ops.ipv6_chk_addr = ipv6_chk_addr;
+	return inet6_register_protosw(&pingv6_protosw);
+}
+
+/* This never gets called because it's not possible to unload the ipv6 module,
+ * but just in case.
+ */
+void pingv6_exit(void)
+{
+	pingv6_ops.ipv6_recv_error = dummy_ipv6_recv_error;
+	pingv6_ops.ip6_datagram_recv_common_ctl = dummy_ip6_datagram_recv_ctl;
+	pingv6_ops.ip6_datagram_recv_specific_ctl = dummy_ip6_datagram_recv_ctl;
+	pingv6_ops.icmpv6_err_convert = dummy_icmpv6_err_convert;
+	pingv6_ops.ipv6_icmp_error = dummy_ipv6_icmp_error;
+	pingv6_ops.ipv6_chk_addr = dummy_ipv6_chk_addr;
+#ifdef CONFIG_PROC_FS
+	unregister_pernet_subsys(&ping_v6_net_ops);
+#endif
+	inet6_unregister_protosw(&pingv6_protosw);
+}