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, 1171 insertions, 0 deletions

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
new file mode 100644
index 000000000..d36f1e273
--- /dev/null
+++ b/net/ipv4/ping.c
@@ -0,0 +1,1171 @@
+// 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/udp.c code.
+ *
+ * Authors:	Vasiliy Kulikov / Openwall (for Linux 2.6),
+ *		Pavel Kankovsky (for Linux 2.4.32)
+ *
+ * Pavel gave all rights to bugs to Vasiliy,
+ * none of the bugs are Pavel's now.
+ */
+
+#include <linux/uaccess.h>
+#include <linux/types.h>
+#include <linux/fcntl.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/in.h>
+#include <linux/errno.h>
+#include <linux/timer.h>
+#include <linux/mm.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <net/snmp.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/protocol.h>
+#include <linux/skbuff.h>
+#include <linux/proc_fs.h>
+#include <linux/export.h>
+#include <linux/bpf-cgroup.h>
+#include <net/sock.h>
+#include <net/ping.h>
+#include <net/udp.h>
+#include <net/route.h>
+#include <net/inet_common.h>
+#include <net/checksum.h>
+
+#if IS_ENABLED(CONFIG_IPV6)
+#include <linux/in6.h>
+#include <linux/icmpv6.h>
+#include <net/addrconf.h>
+#include <net/ipv6.h>
+#include <net/transp_v6.h>
+#endif
+
+struct ping_table {
+	struct hlist_head	hash[PING_HTABLE_SIZE];
+	spinlock_t		lock;
+};
+
+static struct ping_table ping_table;
+struct pingv6_ops pingv6_ops;
+
+static inline u32 ping_hashfn(const struct net *net, u32 num, u32 mask)
+{
+	u32 res = (num + net_hash_mix(net)) & mask;
+
+	pr_debug("hash(%u) = %u\n", num, res);
+	return res;
+}
+
+static inline struct hlist_head *ping_hashslot(struct ping_table *table,
+					       struct net *net, unsigned int num)
+{
+	return &table->hash[ping_hashfn(net, num, PING_HTABLE_MASK)];
+}
+
+int ping_get_port(struct sock *sk, unsigned short ident)
+{
+	struct net *net = sock_net(sk);
+	struct inet_sock *isk, *isk2;
+	struct hlist_head *hlist;
+	struct sock *sk2 = NULL;
+
+	isk = inet_sk(sk);
+	spin_lock(&ping_table.lock);
+	if (ident == 0) {
+		u16 result = net->ipv4.ping_port_rover + 1;
+		u32 i;
+
+		for (i = 0; i < (1L << 16); i++, result++) {
+			if (!result)
+				continue; /* avoid zero */
+			hlist = ping_hashslot(&ping_table, net, result);
+			sk_for_each(sk2, hlist) {
+				if (!net_eq(sock_net(sk2), net))
+					continue;
+				isk2 = inet_sk(sk2);
+
+				if (isk2->inet_num == result)
+					goto next_port;
+			}
+
+			/* found */
+			net->ipv4.ping_port_rover = ident = result;
+			break;
+next_port:
+			;
+		}
+		if (i >= (1L << 16))
+			goto fail;
+	} else {
+		hlist = ping_hashslot(&ping_table, net, ident);
+		sk_for_each(sk2, hlist) {
+			if (!net_eq(sock_net(sk2), net))
+				continue;
+			isk2 = inet_sk(sk2);
+
+			/* BUG? Why is this reuse and not reuseaddr? ping.c
+			 * doesn't turn off SO_REUSEADDR, and it doesn't expect
+			 * that other ping processes can steal its packets.
+			 */
+			if ((isk2->inet_num == ident) &&
+			    (sk2 != sk) &&
+			    (!sk2->sk_reuse || !sk->sk_reuse))
+				goto fail;
+		}
+	}
+
+	pr_debug("found port/ident = %d\n", ident);
+	isk->inet_num = ident;
+	if (sk_unhashed(sk)) {
+		pr_debug("was not hashed\n");
+		sk_add_node_rcu(sk, hlist);
+		sock_set_flag(sk, SOCK_RCU_FREE);
+		sock_prot_inuse_add(net, sk->sk_prot, 1);
+	}
+	spin_unlock(&ping_table.lock);
+	return 0;
+
+fail:
+	spin_unlock(&ping_table.lock);
+	return -EADDRINUSE;
+}
+
+void ping_unhash(struct sock *sk)
+{
+	struct inet_sock *isk = inet_sk(sk);
+
+	pr_debug("ping_unhash(isk=%p,isk->num=%u)\n", isk, isk->inet_num);
+	spin_lock(&ping_table.lock);
+	if (sk_del_node_init_rcu(sk)) {
+		WRITE_ONCE(isk->inet_num, 0);
+		isk->inet_sport = 0;
+		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+	}
+	spin_unlock(&ping_table.lock);
+}
+
+/* Called under rcu_read_lock() */
+static struct sock *ping_lookup(struct net *net, struct sk_buff *skb, u16 ident)
+{
+	struct hlist_head *hslot = ping_hashslot(&ping_table, net, ident);
+	struct sock *sk = NULL;
+	struct inet_sock *isk;
+	int dif, sdif;
+
+	if (skb->protocol == htons(ETH_P_IP)) {
+		dif = inet_iif(skb);
+		sdif = inet_sdif(skb);
+		pr_debug("try to find: num = %d, daddr = %pI4, dif = %d\n",
+			 (int)ident, &ip_hdr(skb)->daddr, dif);
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (skb->protocol == htons(ETH_P_IPV6)) {
+		dif = inet6_iif(skb);
+		sdif = inet6_sdif(skb);
+		pr_debug("try to find: num = %d, daddr = %pI6c, dif = %d\n",
+			 (int)ident, &ipv6_hdr(skb)->daddr, dif);
+#endif
+	} else {
+		return NULL;
+	}
+
+	sk_for_each_rcu(sk, hslot) {
+		int bound_dev_if;
+
+		if (!net_eq(sock_net(sk), net))
+			continue;
+		isk = inet_sk(sk);
+
+		pr_debug("iterate\n");
+		if (READ_ONCE(isk->inet_num) != ident)
+			continue;
+
+		bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+		if (skb->protocol == htons(ETH_P_IP) &&
+		    sk->sk_family == AF_INET) {
+			__be32 rcv_saddr = READ_ONCE(isk->inet_rcv_saddr);
+
+			pr_debug("found: %p: num=%d, daddr=%pI4, dif=%d\n", sk,
+				 ident, &rcv_saddr,
+				 bound_dev_if);
+
+			if (rcv_saddr && rcv_saddr != ip_hdr(skb)->daddr)
+				continue;
+#if IS_ENABLED(CONFIG_IPV6)
+		} else if (skb->protocol == htons(ETH_P_IPV6) &&
+			   sk->sk_family == AF_INET6) {
+
+			pr_debug("found: %p: num=%d, daddr=%pI6c, dif=%d\n", sk,
+				 ident,
+				 &sk->sk_v6_rcv_saddr,
+				 bound_dev_if);
+
+			if (!ipv6_addr_any(&sk->sk_v6_rcv_saddr) &&
+			    !ipv6_addr_equal(&sk->sk_v6_rcv_saddr,
+					     &ipv6_hdr(skb)->daddr))
+				continue;
+#endif
+		} else {
+			continue;
+		}
+
+		if (bound_dev_if && bound_dev_if != dif &&
+		    bound_dev_if != sdif)
+			continue;
+
+		goto exit;
+	}
+
+	sk = NULL;
+exit:
+
+	return sk;
+}
+
+static void inet_get_ping_group_range_net(struct net *net, kgid_t *low,
+					  kgid_t *high)
+{
+	kgid_t *data = net->ipv4.ping_group_range.range;
+	unsigned int seq;
+
+	do {
+		seq = read_seqbegin(&net->ipv4.ping_group_range.lock);
+
+		*low = data[0];
+		*high = data[1];
+	} while (read_seqretry(&net->ipv4.ping_group_range.lock, seq));
+}
+
+
+int ping_init_sock(struct sock *sk)
+{
+	struct net *net = sock_net(sk);
+	kgid_t group = current_egid();
+	struct group_info *group_info;
+	int i;
+	kgid_t low, high;
+	int ret = 0;
+
+	if (sk->sk_family == AF_INET6)
+		sk->sk_ipv6only = 1;
+
+	inet_get_ping_group_range_net(net, &low, &high);
+	if (gid_lte(low, group) && gid_lte(group, high))
+		return 0;
+
+	group_info = get_current_groups();
+	for (i = 0; i < group_info->ngroups; i++) {
+		kgid_t gid = group_info->gid[i];
+
+		if (gid_lte(low, gid) && gid_lte(gid, high))
+			goto out_release_group;
+	}
+
+	ret = -EACCES;
+
+out_release_group:
+	put_group_info(group_info);
+	return ret;
+}
+
+void ping_close(struct sock *sk, long timeout)
+{
+	pr_debug("ping_close(sk=%p,sk->num=%u)\n",
+		 inet_sk(sk), inet_sk(sk)->inet_num);
+	pr_debug("isk->refcnt = %d\n", refcount_read(&sk->sk_refcnt));
+
+	sk_common_release(sk);
+}
+
+static int ping_pre_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
+			    int addr_len)
+{
+	/* This check is replicated from __ip4_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 < sizeof(struct sockaddr_in))
+		return -EINVAL;
+
+	return BPF_CGROUP_RUN_PROG_INET4_CONNECT_LOCK(sk, uaddr, &addr_len);
+}
+
+/* Checks the bind address and possibly modifies sk->sk_bound_dev_if. */
+static int ping_check_bind_addr(struct sock *sk, struct inet_sock *isk,
+				struct sockaddr_unsized *uaddr, int addr_len)
+{
+	struct net *net = sock_net(sk);
+	if (sk->sk_family == AF_INET) {
+		struct sockaddr_in *addr = (struct sockaddr_in *) uaddr;
+		u32 tb_id = RT_TABLE_LOCAL;
+		int chk_addr_ret;
+
+		if (addr_len < sizeof(*addr))
+			return -EINVAL;
+
+		if (addr->sin_family != AF_INET &&
+		    !(addr->sin_family == AF_UNSPEC &&
+		      addr->sin_addr.s_addr == htonl(INADDR_ANY)))
+			return -EAFNOSUPPORT;
+
+		pr_debug("ping_check_bind_addr(sk=%p,addr=%pI4,port=%d)\n",
+			 sk, &addr->sin_addr.s_addr, ntohs(addr->sin_port));
+
+		if (addr->sin_addr.s_addr == htonl(INADDR_ANY))
+			return 0;
+
+		tb_id = l3mdev_fib_table_by_index(net, sk->sk_bound_dev_if) ? : tb_id;
+		chk_addr_ret = inet_addr_type_table(net, addr->sin_addr.s_addr, tb_id);
+
+		if (chk_addr_ret == RTN_MULTICAST ||
+		    chk_addr_ret == RTN_BROADCAST ||
+		    (chk_addr_ret != RTN_LOCAL &&
+		     !inet_can_nonlocal_bind(net, isk)))
+			return -EADDRNOTAVAIL;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (sk->sk_family == AF_INET6) {
+		struct sockaddr_in6 *addr = (struct sockaddr_in6 *) uaddr;
+		int addr_type, scoped, has_addr;
+		struct net_device *dev = NULL;
+
+		if (addr_len < sizeof(*addr))
+			return -EINVAL;
+
+		if (addr->sin6_family != AF_INET6)
+			return -EAFNOSUPPORT;
+
+		pr_debug("ping_check_bind_addr(sk=%p,addr=%pI6c,port=%d)\n",
+			 sk, addr->sin6_addr.s6_addr, ntohs(addr->sin6_port));
+
+		addr_type = ipv6_addr_type(&addr->sin6_addr);
+		scoped = __ipv6_addr_needs_scope_id(addr_type);
+		if ((addr_type != IPV6_ADDR_ANY &&
+		     !(addr_type & IPV6_ADDR_UNICAST)) ||
+		    (scoped && !addr->sin6_scope_id))
+			return -EINVAL;
+
+		rcu_read_lock();
+		if (addr->sin6_scope_id) {
+			dev = dev_get_by_index_rcu(net, addr->sin6_scope_id);
+			if (!dev) {
+				rcu_read_unlock();
+				return -ENODEV;
+			}
+		}
+
+		if (!dev && sk->sk_bound_dev_if) {
+			dev = dev_get_by_index_rcu(net, sk->sk_bound_dev_if);
+			if (!dev) {
+				rcu_read_unlock();
+				return -ENODEV;
+			}
+		}
+		has_addr = pingv6_ops.ipv6_chk_addr(net, &addr->sin6_addr, dev,
+						    scoped);
+		rcu_read_unlock();
+
+		if (!(ipv6_can_nonlocal_bind(net, isk) || has_addr ||
+		      addr_type == IPV6_ADDR_ANY))
+			return -EADDRNOTAVAIL;
+
+		if (scoped)
+			sk->sk_bound_dev_if = addr->sin6_scope_id;
+#endif
+	} else {
+		return -EAFNOSUPPORT;
+	}
+	return 0;
+}
+
+static void ping_set_saddr(struct sock *sk, struct sockaddr_unsized *saddr)
+{
+	if (saddr->sa_family == AF_INET) {
+		struct inet_sock *isk = inet_sk(sk);
+		struct sockaddr_in *addr = (struct sockaddr_in *) saddr;
+
+		isk->inet_saddr = addr->sin_addr.s_addr;
+		WRITE_ONCE(isk->inet_rcv_saddr, addr->sin_addr.s_addr);
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (saddr->sa_family == AF_INET6) {
+		struct sockaddr_in6 *addr = (struct sockaddr_in6 *) saddr;
+		struct ipv6_pinfo *np = inet6_sk(sk);
+		sk->sk_v6_rcv_saddr = np->saddr = addr->sin6_addr;
+#endif
+	}
+}
+
+/*
+ * We need our own bind because there are no privileged id's == local ports.
+ * Moreover, we don't allow binding to multi- and broadcast addresses.
+ */
+
+int ping_bind(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len)
+{
+	struct inet_sock *isk = inet_sk(sk);
+	unsigned short snum;
+	int err;
+	int dif = sk->sk_bound_dev_if;
+
+	err = ping_check_bind_addr(sk, isk, uaddr, addr_len);
+	if (err)
+		return err;
+
+	lock_sock(sk);
+
+	err = -EINVAL;
+	if (isk->inet_num != 0)
+		goto out;
+
+	err = -EADDRINUSE;
+	snum = ntohs(((struct sockaddr_in *)uaddr)->sin_port);
+	if (ping_get_port(sk, snum) != 0) {
+		/* Restore possibly modified sk->sk_bound_dev_if by ping_check_bind_addr(). */
+		sk->sk_bound_dev_if = dif;
+		goto out;
+	}
+	ping_set_saddr(sk, uaddr);
+
+	pr_debug("after bind(): num = %hu, dif = %d\n",
+		 isk->inet_num,
+		 sk->sk_bound_dev_if);
+
+	err = 0;
+	if (sk->sk_family == AF_INET && isk->inet_rcv_saddr)
+		sk->sk_userlocks |= SOCK_BINDADDR_LOCK;
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == AF_INET6 && !ipv6_addr_any(&sk->sk_v6_rcv_saddr))
+		sk->sk_userlocks |= SOCK_BINDADDR_LOCK;
+#endif
+
+	if (snum)
+		sk->sk_userlocks |= SOCK_BINDPORT_LOCK;
+	isk->inet_sport = htons(isk->inet_num);
+	isk->inet_daddr = 0;
+	isk->inet_dport = 0;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == AF_INET6)
+		memset(&sk->sk_v6_daddr, 0, sizeof(sk->sk_v6_daddr));
+#endif
+
+	sk_dst_reset(sk);
+out:
+	release_sock(sk);
+	pr_debug("ping_v4_bind -> %d\n", err);
+	return err;
+}
+
+/*
+ * Is this a supported type of ICMP message?
+ */
+
+static inline int ping_supported(int family, int type, int code)
+{
+	return (family == AF_INET && type == ICMP_ECHO && code == 0) ||
+	       (family == AF_INET && type == ICMP_EXT_ECHO && code == 0) ||
+	       (family == AF_INET6 && type == ICMPV6_ECHO_REQUEST && code == 0) ||
+	       (family == AF_INET6 && type == ICMPV6_EXT_ECHO_REQUEST && code == 0);
+}
+
+/*
+ * This routine is called by the ICMP module when it gets some
+ * sort of error condition.
+ */
+
+void ping_err(struct sk_buff *skb, int offset, u32 info)
+{
+	int family;
+	struct icmphdr *icmph;
+	struct inet_sock *inet_sock;
+	int type;
+	int code;
+	struct net *net = dev_net(skb->dev);
+	struct sock *sk;
+	int harderr;
+	int err;
+
+	if (skb->protocol == htons(ETH_P_IP)) {
+		family = AF_INET;
+		type = icmp_hdr(skb)->type;
+		code = icmp_hdr(skb)->code;
+		icmph = (struct icmphdr *)(skb->data + offset);
+	} else if (skb->protocol == htons(ETH_P_IPV6)) {
+		family = AF_INET6;
+		type = icmp6_hdr(skb)->icmp6_type;
+		code = icmp6_hdr(skb)->icmp6_code;
+		icmph = (struct icmphdr *) (skb->data + offset);
+	} else {
+		BUG();
+	}
+
+	/* We assume the packet has already been checked by icmp_unreach */
+
+	if (!ping_supported(family, icmph->type, icmph->code))
+		return;
+
+	pr_debug("ping_err(proto=0x%x,type=%d,code=%d,id=%04x,seq=%04x)\n",
+		 skb->protocol, type, code, ntohs(icmph->un.echo.id),
+		 ntohs(icmph->un.echo.sequence));
+
+	sk = ping_lookup(net, skb, ntohs(icmph->un.echo.id));
+	if (!sk) {
+		pr_debug("no socket, dropping\n");
+		return;	/* No socket for error */
+	}
+	pr_debug("err on socket %p\n", sk);
+
+	err = 0;
+	harderr = 0;
+	inet_sock = inet_sk(sk);
+
+	if (skb->protocol == htons(ETH_P_IP)) {
+		switch (type) {
+		default:
+		case ICMP_TIME_EXCEEDED:
+			err = EHOSTUNREACH;
+			break;
+		case ICMP_SOURCE_QUENCH:
+			/* This is not a real error but ping wants to see it.
+			 * Report it with some fake errno.
+			 */
+			err = EREMOTEIO;
+			break;
+		case ICMP_PARAMETERPROB:
+			err = EPROTO;
+			harderr = 1;
+			break;
+		case ICMP_DEST_UNREACH:
+			if (code == ICMP_FRAG_NEEDED) { /* Path MTU discovery */
+				ipv4_sk_update_pmtu(skb, sk, info);
+				if (READ_ONCE(inet_sock->pmtudisc) != IP_PMTUDISC_DONT) {
+					err = EMSGSIZE;
+					harderr = 1;
+					break;
+				}
+				goto out;
+			}
+			err = EHOSTUNREACH;
+			if (code <= NR_ICMP_UNREACH) {
+				harderr = icmp_err_convert[code].fatal;
+				err = icmp_err_convert[code].errno;
+			}
+			break;
+		case ICMP_REDIRECT:
+			/* See ICMP_SOURCE_QUENCH */
+			ipv4_sk_redirect(skb, sk);
+			err = EREMOTEIO;
+			break;
+		}
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (skb->protocol == htons(ETH_P_IPV6)) {
+		harderr = pingv6_ops.icmpv6_err_convert(type, code, &err);
+#endif
+	}
+
+	/*
+	 *      RFC1122: OK.  Passes ICMP errors back to application, as per
+	 *	4.1.3.3.
+	 */
+	if ((family == AF_INET && !inet_test_bit(RECVERR, sk)) ||
+	    (family == AF_INET6 && !inet6_test_bit(RECVERR6, sk))) {
+		if (!harderr || sk->sk_state != TCP_ESTABLISHED)
+			goto out;
+	} else {
+		if (family == AF_INET) {
+			ip_icmp_error(sk, skb, err, 0 /* no remote port */,
+				      info, (u8 *)icmph);
+#if IS_ENABLED(CONFIG_IPV6)
+		} else if (family == AF_INET6) {
+			pingv6_ops.ipv6_icmp_error(sk, skb, err, 0,
+						   info, (u8 *)icmph);
+#endif
+		}
+	}
+	sk->sk_err = err;
+	sk_error_report(sk);
+out:
+	return;
+}
+
+/*
+ *	Copy and checksum an ICMP Echo packet from user space into a buffer
+ *	starting from the payload.
+ */
+
+int ping_getfrag(void *from, char *to,
+		 int offset, int fraglen, int odd, struct sk_buff *skb)
+{
+	struct pingfakehdr *pfh = from;
+
+	if (!csum_and_copy_from_iter_full(to, fraglen, &pfh->wcheck,
+					  &pfh->msg->msg_iter))
+		return -EFAULT;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	/* For IPv6, checksum each skb as we go along, as expected by
+	 * icmpv6_push_pending_frames. For IPv4, accumulate the checksum in
+	 * wcheck, it will be finalized in ping_v4_push_pending_frames.
+	 */
+	if (pfh->family == AF_INET6) {
+		skb->csum = csum_block_add(skb->csum, pfh->wcheck, odd);
+		skb->ip_summed = CHECKSUM_NONE;
+		pfh->wcheck = 0;
+	}
+#endif
+
+	return 0;
+}
+
+static int ping_v4_push_pending_frames(struct sock *sk, struct pingfakehdr *pfh,
+				       struct flowi4 *fl4)
+{
+	struct sk_buff *skb = skb_peek(&sk->sk_write_queue);
+
+	if (!skb)
+		return 0;
+	pfh->wcheck = csum_partial((char *)&pfh->icmph,
+		sizeof(struct icmphdr), pfh->wcheck);
+	pfh->icmph.checksum = csum_fold(pfh->wcheck);
+	memcpy(icmp_hdr(skb), &pfh->icmph, sizeof(struct icmphdr));
+	skb->ip_summed = CHECKSUM_NONE;
+	return ip_push_pending_frames(sk, fl4);
+}
+
+int ping_common_sendmsg(int family, struct msghdr *msg, size_t len,
+			void *user_icmph, size_t icmph_len)
+{
+	u8 type, code;
+
+	if (len > 0xFFFF)
+		return -EMSGSIZE;
+
+	/* Must have at least a full ICMP header. */
+	if (len < icmph_len)
+		return -EINVAL;
+
+	/*
+	 *	Check the flags.
+	 */
+
+	/* Mirror BSD error message compatibility */
+	if (msg->msg_flags & MSG_OOB)
+		return -EOPNOTSUPP;
+
+	/*
+	 *	Fetch the ICMP header provided by the userland.
+	 *	iovec is modified! The ICMP header is consumed.
+	 */
+	if (memcpy_from_msg(user_icmph, msg, icmph_len))
+		return -EFAULT;
+
+	if (family == AF_INET) {
+		type = ((struct icmphdr *) user_icmph)->type;
+		code = ((struct icmphdr *) user_icmph)->code;
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (family == AF_INET6) {
+		type = ((struct icmp6hdr *) user_icmph)->icmp6_type;
+		code = ((struct icmp6hdr *) user_icmph)->icmp6_code;
+#endif
+	} else {
+		BUG();
+	}
+
+	if (!ping_supported(family, type, code))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int ping_v4_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
+{
+	DEFINE_RAW_FLEX(struct ip_options_rcu, opt_copy, opt.__data,
+			IP_OPTIONS_DATA_FIXED_SIZE);
+	struct net *net = sock_net(sk);
+	struct flowi4 fl4;
+	struct inet_sock *inet = inet_sk(sk);
+	struct ipcm_cookie ipc;
+	struct icmphdr user_icmph;
+	struct pingfakehdr pfh;
+	struct rtable *rt = NULL;
+	int free = 0;
+	__be32 saddr, daddr, faddr;
+	u8 scope;
+	int err;
+
+	pr_debug("ping_v4_sendmsg(sk=%p,sk->num=%u)\n", inet, inet->inet_num);
+
+	err = ping_common_sendmsg(AF_INET, msg, len, &user_icmph,
+				  sizeof(user_icmph));
+	if (err)
+		return err;
+
+	/*
+	 *	Get and verify the address.
+	 */
+
+	if (msg->msg_name) {
+		DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
+		if (msg->msg_namelen < sizeof(*usin))
+			return -EINVAL;
+		if (usin->sin_family != AF_INET)
+			return -EAFNOSUPPORT;
+		daddr = usin->sin_addr.s_addr;
+		/* no remote port */
+	} else {
+		if (sk->sk_state != TCP_ESTABLISHED)
+			return -EDESTADDRREQ;
+		daddr = inet->inet_daddr;
+		/* no remote port */
+	}
+
+	ipcm_init_sk(&ipc, inet);
+
+	if (msg->msg_controllen) {
+		err = ip_cmsg_send(sk, msg, &ipc, false);
+		if (unlikely(err)) {
+			kfree(ipc.opt);
+			return err;
+		}
+		if (ipc.opt)
+			free = 1;
+	}
+	if (!ipc.opt) {
+		struct ip_options_rcu *inet_opt;
+
+		rcu_read_lock();
+		inet_opt = rcu_dereference(inet->inet_opt);
+		if (inet_opt) {
+			memcpy(opt_copy, inet_opt,
+			       sizeof(*inet_opt) + inet_opt->opt.optlen);
+			ipc.opt = opt_copy;
+		}
+		rcu_read_unlock();
+	}
+
+	saddr = ipc.addr;
+	ipc.addr = faddr = daddr;
+
+	if (ipc.opt && ipc.opt->opt.srr) {
+		if (!daddr) {
+			err = -EINVAL;
+			goto out_free;
+		}
+		faddr = ipc.opt->opt.faddr;
+	}
+	scope = ip_sendmsg_scope(inet, &ipc, msg);
+
+	if (ipv4_is_multicast(daddr)) {
+		if (!ipc.oif || netif_index_is_l3_master(sock_net(sk), ipc.oif))
+			ipc.oif = READ_ONCE(inet->mc_index);
+		if (!saddr)
+			saddr = READ_ONCE(inet->mc_addr);
+	} else if (!ipc.oif)
+		ipc.oif = READ_ONCE(inet->uc_index);
+
+	flowi4_init_output(&fl4, ipc.oif, ipc.sockc.mark,
+			   ipc.tos & INET_DSCP_MASK, scope,
+			   sk->sk_protocol, inet_sk_flowi_flags(sk), faddr,
+			   saddr, 0, 0, sk_uid(sk));
+
+	fl4.fl4_icmp_type = user_icmph.type;
+	fl4.fl4_icmp_code = user_icmph.code;
+
+	security_sk_classify_flow(sk, flowi4_to_flowi_common(&fl4));
+	rt = ip_route_output_flow(net, &fl4, sk);
+	if (IS_ERR(rt)) {
+		err = PTR_ERR(rt);
+		rt = NULL;
+		if (err == -ENETUNREACH)
+			IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
+		goto out;
+	}
+
+	err = -EACCES;
+	if ((rt->rt_flags & RTCF_BROADCAST) &&
+	    !sock_flag(sk, SOCK_BROADCAST))
+		goto out;
+
+	if (msg->msg_flags & MSG_CONFIRM)
+		goto do_confirm;
+back_from_confirm:
+
+	if (!ipc.addr)
+		ipc.addr = fl4.daddr;
+
+	lock_sock(sk);
+
+	pfh.icmph.type = user_icmph.type; /* already checked */
+	pfh.icmph.code = user_icmph.code; /* ditto */
+	pfh.icmph.checksum = 0;
+	pfh.icmph.un.echo.id = inet->inet_sport;
+	pfh.icmph.un.echo.sequence = user_icmph.un.echo.sequence;
+	pfh.msg = msg;
+	pfh.wcheck = 0;
+	pfh.family = AF_INET;
+
+	err = ip_append_data(sk, &fl4, ping_getfrag, &pfh, len,
+			     sizeof(struct icmphdr), &ipc, &rt,
+			     msg->msg_flags);
+	if (err)
+		ip_flush_pending_frames(sk);
+	else
+		err = ping_v4_push_pending_frames(sk, &pfh, &fl4);
+	release_sock(sk);
+
+out:
+	ip_rt_put(rt);
+out_free:
+	if (free)
+		kfree(ipc.opt);
+	if (!err)
+		return len;
+	return err;
+
+do_confirm:
+	if (msg->msg_flags & MSG_PROBE)
+		dst_confirm_neigh(&rt->dst, &fl4.daddr);
+	if (!(msg->msg_flags & MSG_PROBE) || len)
+		goto back_from_confirm;
+	err = 0;
+	goto out;
+}
+
+int ping_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags)
+{
+	struct inet_sock *isk = inet_sk(sk);
+	int family = sk->sk_family;
+	struct sk_buff *skb;
+	int copied, err;
+
+	pr_debug("ping_recvmsg(sk=%p,sk->num=%u)\n", isk,
+		 READ_ONCE(isk->inet_num));
+
+	err = -EOPNOTSUPP;
+	if (flags & MSG_OOB)
+		goto out;
+
+	if (flags & MSG_ERRQUEUE)
+		return inet_recv_error(sk, msg, len);
+
+	skb = skb_recv_datagram(sk, flags, &err);
+	if (!skb)
+		goto out;
+
+	copied = skb->len;
+	if (copied > len) {
+		msg->msg_flags |= MSG_TRUNC;
+		copied = len;
+	}
+
+	/* Don't bother checking the checksum */
+	err = skb_copy_datagram_msg(skb, 0, msg, copied);
+	if (err)
+		goto done;
+
+	sock_recv_timestamp(msg, sk, skb);
+
+	/* Copy the address and add cmsg data. */
+	if (family == AF_INET) {
+		DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
+
+		if (sin) {
+			sin->sin_family = AF_INET;
+			sin->sin_port = 0 /* skb->h.uh->source */;
+			sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
+			memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+			msg->msg_namelen = sizeof(*sin);
+		}
+
+		if (inet_cmsg_flags(isk))
+			ip_cmsg_recv(msg, skb);
+
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (family == AF_INET6) {
+		struct ipv6hdr *ip6 = ipv6_hdr(skb);
+		DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
+
+		if (sin6) {
+			sin6->sin6_family = AF_INET6;
+			sin6->sin6_port = 0;
+			sin6->sin6_addr = ip6->saddr;
+			sin6->sin6_flowinfo = 0;
+			if (inet6_test_bit(SNDFLOW, sk))
+				sin6->sin6_flowinfo = ip6_flowinfo(ip6);
+			sin6->sin6_scope_id =
+				ipv6_iface_scope_id(&sin6->sin6_addr,
+						    inet6_iif(skb));
+			msg->msg_namelen = sizeof(*sin6);
+		}
+
+		if (inet6_sk(sk)->rxopt.all)
+			pingv6_ops.ip6_datagram_recv_common_ctl(sk, msg, skb);
+		if (skb->protocol == htons(ETH_P_IPV6) &&
+		    inet6_sk(sk)->rxopt.all)
+			pingv6_ops.ip6_datagram_recv_specific_ctl(sk, msg, skb);
+		else if (skb->protocol == htons(ETH_P_IP) &&
+			 inet_cmsg_flags(isk))
+			ip_cmsg_recv(msg, skb);
+#endif
+	} else {
+		BUG();
+	}
+
+	err = copied;
+
+done:
+	skb_free_datagram(sk, skb);
+out:
+	pr_debug("ping_recvmsg -> %d\n", err);
+	return err;
+}
+
+static enum skb_drop_reason __ping_queue_rcv_skb(struct sock *sk,
+						 struct sk_buff *skb)
+{
+	enum skb_drop_reason reason;
+
+	pr_debug("ping_queue_rcv_skb(sk=%p,sk->num=%d,skb=%p)\n",
+		 inet_sk(sk), inet_sk(sk)->inet_num, skb);
+	reason = sock_queue_rcv_skb_reason(sk, skb);
+	if (reason) {
+		sk_skb_reason_drop(sk, skb, reason);
+		pr_debug("ping_queue_rcv_skb -> failed\n");
+		return reason;
+	}
+	return SKB_NOT_DROPPED_YET;
+}
+
+int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
+{
+	return __ping_queue_rcv_skb(sk, skb) ? -1 : 0;
+}
+
+
+/*
+ *	All we need to do is get the socket.
+ */
+
+enum skb_drop_reason ping_rcv(struct sk_buff *skb)
+{
+	struct net *net = dev_net(skb->dev);
+	struct icmphdr *icmph = icmp_hdr(skb);
+	struct sock *sk;
+
+	/* We assume the packet has already been checked by icmp_rcv */
+
+	pr_debug("ping_rcv(skb=%p,id=%04x,seq=%04x)\n",
+		 skb, ntohs(icmph->un.echo.id), ntohs(icmph->un.echo.sequence));
+
+	/* Push ICMP header back */
+	skb_push(skb, skb->data - (u8 *)icmph);
+
+	sk = ping_lookup(net, skb, ntohs(icmph->un.echo.id));
+	if (sk)
+		return __ping_queue_rcv_skb(sk, skb);
+
+	kfree_skb_reason(skb, SKB_DROP_REASON_NO_SOCKET);
+	return SKB_DROP_REASON_NO_SOCKET;
+}
+
+struct proto ping_prot = {
+	.name =		"PING",
+	.owner =	THIS_MODULE,
+	.init =		ping_init_sock,
+	.close =	ping_close,
+	.pre_connect =	ping_pre_connect,
+	.connect =	ip4_datagram_connect,
+	.disconnect =	__udp_disconnect,
+	.setsockopt =	ip_setsockopt,
+	.getsockopt =	ip_getsockopt,
+	.sendmsg =	ping_v4_sendmsg,
+	.recvmsg =	ping_recvmsg,
+	.bind =		ping_bind,
+	.backlog_rcv =	ping_queue_rcv_skb,
+	.release_cb =	ip4_datagram_release_cb,
+	.unhash =	ping_unhash,
+	.get_port =	ping_get_port,
+	.put_port =	ping_unhash,
+	.obj_size =	sizeof(struct inet_sock),
+};
+
+#ifdef CONFIG_PROC_FS
+
+static struct sock *ping_get_first(struct seq_file *seq, int start)
+{
+	struct sock *sk;
+	struct ping_iter_state *state = seq->private;
+	struct net *net = seq_file_net(seq);
+
+	for (state->bucket = start; state->bucket < PING_HTABLE_SIZE;
+	     ++state->bucket) {
+		struct hlist_head *hslot;
+
+		hslot = &ping_table.hash[state->bucket];
+
+		if (hlist_empty(hslot))
+			continue;
+
+		sk_for_each(sk, hslot) {
+			if (net_eq(sock_net(sk), net) &&
+			    sk->sk_family == state->family)
+				goto found;
+		}
+	}
+	sk = NULL;
+found:
+	return sk;
+}
+
+static struct sock *ping_get_next(struct seq_file *seq, struct sock *sk)
+{
+	struct ping_iter_state *state = seq->private;
+	struct net *net = seq_file_net(seq);
+
+	do {
+		sk = sk_next(sk);
+	} while (sk && (!net_eq(sock_net(sk), net)));
+
+	if (!sk)
+		return ping_get_first(seq, state->bucket + 1);
+	return sk;
+}
+
+static struct sock *ping_get_idx(struct seq_file *seq, loff_t pos)
+{
+	struct sock *sk = ping_get_first(seq, 0);
+
+	if (sk)
+		while (pos && (sk = ping_get_next(seq, sk)) != NULL)
+			--pos;
+	return pos ? NULL : sk;
+}
+
+void *ping_seq_start(struct seq_file *seq, loff_t *pos, sa_family_t family)
+	__acquires(ping_table.lock)
+{
+	struct ping_iter_state *state = seq->private;
+	state->bucket = 0;
+	state->family = family;
+
+	spin_lock(&ping_table.lock);
+
+	return *pos ? ping_get_idx(seq, *pos-1) : SEQ_START_TOKEN;
+}
+
+static void *ping_v4_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	return ping_seq_start(seq, pos, AF_INET);
+}
+
+void *ping_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct sock *sk;
+
+	if (v == SEQ_START_TOKEN)
+		sk = ping_get_idx(seq, 0);
+	else
+		sk = ping_get_next(seq, v);
+
+	++*pos;
+	return sk;
+}
+
+void ping_seq_stop(struct seq_file *seq, void *v)
+	__releases(ping_table.lock)
+{
+	spin_unlock(&ping_table.lock);
+}
+
+static void ping_v4_format_sock(struct sock *sp, struct seq_file *f,
+		int bucket)
+{
+	struct inet_sock *inet = inet_sk(sp);
+	__be32 dest = inet->inet_daddr;
+	__be32 src = inet->inet_rcv_saddr;
+	__u16 destp = ntohs(inet->inet_dport);
+	__u16 srcp = ntohs(inet->inet_sport);
+
+	seq_printf(f, "%5d: %08X:%04X %08X:%04X"
+		" %02X %08X:%08X %02X:%08lX %08X %5u %8d %llu %d %pK %u",
+		bucket, src, srcp, dest, destp, sp->sk_state,
+		sk_wmem_alloc_get(sp),
+		sk_rmem_alloc_get(sp),
+		0, 0L, 0,
+		from_kuid_munged(seq_user_ns(f), sk_uid(sp)),
+		0, sock_i_ino(sp),
+		refcount_read(&sp->sk_refcnt), sp,
+		sk_drops_read(sp));
+}
+
+static int ping_v4_seq_show(struct seq_file *seq, void *v)
+{
+	seq_setwidth(seq, 127);
+	if (v == SEQ_START_TOKEN)
+		seq_puts(seq, "  sl  local_address rem_address   st tx_queue "
+			   "rx_queue tr tm->when retrnsmt   uid  timeout "
+			   "inode ref pointer drops");
+	else {
+		struct ping_iter_state *state = seq->private;
+
+		ping_v4_format_sock(v, seq, state->bucket);
+	}
+	seq_pad(seq, '\n');
+	return 0;
+}
+
+static const struct seq_operations ping_v4_seq_ops = {
+	.start		= ping_v4_seq_start,
+	.show		= ping_v4_seq_show,
+	.next		= ping_seq_next,
+	.stop		= ping_seq_stop,
+};
+
+static int __net_init ping_v4_proc_init_net(struct net *net)
+{
+	if (!proc_create_net("icmp", 0444, net->proc_net, &ping_v4_seq_ops,
+			sizeof(struct ping_iter_state)))
+		return -ENOMEM;
+
+	net->ipv4.ping_port_rover = get_random_u16();
+	return 0;
+}
+
+static void __net_exit ping_v4_proc_exit_net(struct net *net)
+{
+	remove_proc_entry("icmp", net->proc_net);
+}
+
+static struct pernet_operations ping_v4_net_ops = {
+	.init = ping_v4_proc_init_net,
+	.exit = ping_v4_proc_exit_net,
+};
+
+int __init ping_proc_init(void)
+{
+	return register_pernet_subsys(&ping_v4_net_ops);
+}
+
+void ping_proc_exit(void)
+{
+	unregister_pernet_subsys(&ping_v4_net_ops);
+}
+
+#endif
+
+void __init ping_init(void)
+{
+	int i;
+
+	for (i = 0; i < PING_HTABLE_SIZE; i++)
+		INIT_HLIST_HEAD(&ping_table.hash[i]);
+	spin_lock_init(&ping_table.lock);
+}