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, 857 insertions, 0 deletions

diff --git a/net/atm/common.c b/net/atm/common.c
new file mode 100644
index 000000000..81195727f
--- /dev/null
+++ b/net/atm/common.c
@@ -0,0 +1,857 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* net/atm/common.c - ATM sockets (common part for PVC and SVC) */
+
+/* Written 1995-2000 by Werner Almesberger, EPFL LRC/ICA */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
+
+#include <linux/module.h>
+#include <linux/kmod.h>
+#include <linux/net.h>		/* struct socket, struct proto_ops */
+#include <linux/atm.h>		/* ATM stuff */
+#include <linux/atmdev.h>
+#include <linux/socket.h>	/* SOL_SOCKET */
+#include <linux/errno.h>	/* error codes */
+#include <linux/capability.h>
+#include <linux/mm.h>
+#include <linux/sched/signal.h>
+#include <linux/time64.h>	/* 64-bit time for seconds */
+#include <linux/skbuff.h>
+#include <linux/bitops.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <net/sock.h>		/* struct sock */
+#include <linux/uaccess.h>
+#include <linux/poll.h>
+#include <linux/uio.h>
+
+#include <linux/atomic.h>
+
+#include "resources.h"		/* atm_find_dev */
+#include "common.h"		/* prototypes */
+#include "protocols.h"		/* atm_init_<transport> */
+
+struct hlist_head vcc_hash[VCC_HTABLE_SIZE];
+EXPORT_SYMBOL(vcc_hash);
+
+DEFINE_RWLOCK(vcc_sklist_lock);
+EXPORT_SYMBOL(vcc_sklist_lock);
+
+static ATOMIC_NOTIFIER_HEAD(atm_dev_notify_chain);
+
+static void __vcc_insert_socket(struct sock *sk)
+{
+	struct atm_vcc *vcc = atm_sk(sk);
+	struct hlist_head *head = &vcc_hash[vcc->vci & (VCC_HTABLE_SIZE - 1)];
+	sk->sk_hash = vcc->vci & (VCC_HTABLE_SIZE - 1);
+	sk_add_node(sk, head);
+}
+
+void vcc_insert_socket(struct sock *sk)
+{
+	write_lock_irq(&vcc_sklist_lock);
+	__vcc_insert_socket(sk);
+	write_unlock_irq(&vcc_sklist_lock);
+}
+EXPORT_SYMBOL(vcc_insert_socket);
+
+static void vcc_remove_socket(struct sock *sk)
+{
+	write_lock_irq(&vcc_sklist_lock);
+	sk_del_node_init(sk);
+	write_unlock_irq(&vcc_sklist_lock);
+}
+
+static bool vcc_tx_ready(struct atm_vcc *vcc, unsigned int size)
+{
+	struct sock *sk = sk_atm(vcc);
+
+	if (sk_wmem_alloc_get(sk) && !atm_may_send(vcc, size)) {
+		pr_debug("Sorry: wmem_alloc = %d, size = %d, sndbuf = %d\n",
+			 sk_wmem_alloc_get(sk), size, sk->sk_sndbuf);
+		return false;
+	}
+	return true;
+}
+
+static void vcc_sock_destruct(struct sock *sk)
+{
+	if (atomic_read(&sk->sk_rmem_alloc))
+		printk(KERN_DEBUG "%s: rmem leakage (%d bytes) detected.\n",
+		       __func__, atomic_read(&sk->sk_rmem_alloc));
+
+	if (refcount_read(&sk->sk_wmem_alloc))
+		printk(KERN_DEBUG "%s: wmem leakage (%d bytes) detected.\n",
+		       __func__, refcount_read(&sk->sk_wmem_alloc));
+}
+
+static void vcc_def_wakeup(struct sock *sk)
+{
+	struct socket_wq *wq;
+
+	rcu_read_lock();
+	wq = rcu_dereference(sk->sk_wq);
+	if (skwq_has_sleeper(wq))
+		wake_up(&wq->wait);
+	rcu_read_unlock();
+}
+
+static inline int vcc_writable(struct sock *sk)
+{
+	struct atm_vcc *vcc = atm_sk(sk);
+
+	return (vcc->qos.txtp.max_sdu +
+		refcount_read(&sk->sk_wmem_alloc)) <= sk->sk_sndbuf;
+}
+
+static void vcc_write_space(struct sock *sk)
+{
+	struct socket_wq *wq;
+
+	rcu_read_lock();
+
+	if (vcc_writable(sk)) {
+		wq = rcu_dereference(sk->sk_wq);
+		if (skwq_has_sleeper(wq))
+			wake_up_interruptible(&wq->wait);
+
+		sk_wake_async_rcu(sk, SOCK_WAKE_SPACE, POLL_OUT);
+	}
+
+	rcu_read_unlock();
+}
+
+static void vcc_release_cb(struct sock *sk)
+{
+	struct atm_vcc *vcc = atm_sk(sk);
+
+	if (vcc->release_cb)
+		vcc->release_cb(vcc);
+}
+
+static struct proto vcc_proto = {
+	.name	  = "VCC",
+	.owner	  = THIS_MODULE,
+	.obj_size = sizeof(struct atm_vcc),
+	.release_cb = vcc_release_cb,
+};
+
+int vcc_create(struct net *net, struct socket *sock, int protocol, int family, int kern)
+{
+	struct sock *sk;
+	struct atm_vcc *vcc;
+
+	sock->sk = NULL;
+	if (sock->type == SOCK_STREAM)
+		return -EINVAL;
+	sk = sk_alloc(net, family, GFP_KERNEL, &vcc_proto, kern);
+	if (!sk)
+		return -ENOMEM;
+	sock_init_data(sock, sk);
+	sk->sk_state_change = vcc_def_wakeup;
+	sk->sk_write_space = vcc_write_space;
+
+	vcc = atm_sk(sk);
+	vcc->dev = NULL;
+	vcc->qos.txtp.max_sdu = 1 << 16; /* for meta VCs */
+	refcount_set(&sk->sk_wmem_alloc, SK_WMEM_ALLOC_BIAS);
+	atomic_set(&sk->sk_rmem_alloc, 0);
+	vcc->push = NULL;
+	vcc->pop = NULL;
+	vcc->owner = NULL;
+	vcc->release_cb = NULL;
+	vcc->vpi = vcc->vci = 0; /* no VCI/VPI yet */
+	vcc->atm_options = vcc->aal_options = 0;
+	sk->sk_destruct = vcc_sock_destruct;
+	return 0;
+}
+
+static void vcc_destroy_socket(struct sock *sk)
+{
+	struct atm_vcc *vcc = atm_sk(sk);
+	struct sk_buff *skb;
+
+	set_bit(ATM_VF_CLOSE, &vcc->flags);
+	clear_bit(ATM_VF_READY, &vcc->flags);
+	if (vcc->dev && vcc->dev->ops->close)
+		vcc->dev->ops->close(vcc);
+	if (vcc->push)
+		vcc->push(vcc, NULL); /* atmarpd has no push */
+	module_put(vcc->owner);
+
+	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+		atm_return(vcc, skb->truesize);
+		kfree_skb(skb);
+	}
+
+	if (vcc->dev && vcc->dev->ops->owner) {
+		module_put(vcc->dev->ops->owner);
+		atm_dev_put(vcc->dev);
+	}
+
+	vcc_remove_socket(sk);
+}
+
+int vcc_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+
+	if (sk) {
+		lock_sock(sk);
+		vcc_destroy_socket(sock->sk);
+		release_sock(sk);
+		sock_put(sk);
+	}
+
+	return 0;
+}
+
+void vcc_release_async(struct atm_vcc *vcc, int reply)
+{
+	struct sock *sk = sk_atm(vcc);
+
+	set_bit(ATM_VF_CLOSE, &vcc->flags);
+	sk->sk_shutdown |= RCV_SHUTDOWN;
+	sk->sk_err = -reply;
+	sk->sk_state_change(sk);
+}
+EXPORT_SYMBOL(vcc_release_async);
+
+void vcc_process_recv_queue(struct atm_vcc *vcc)
+{
+	struct sk_buff_head queue, *rq;
+	struct sk_buff *skb, *tmp;
+	unsigned long flags;
+
+	__skb_queue_head_init(&queue);
+	rq = &sk_atm(vcc)->sk_receive_queue;
+
+	spin_lock_irqsave(&rq->lock, flags);
+	skb_queue_splice_init(rq, &queue);
+	spin_unlock_irqrestore(&rq->lock, flags);
+
+	skb_queue_walk_safe(&queue, skb, tmp) {
+		__skb_unlink(skb, &queue);
+		vcc->push(vcc, skb);
+	}
+}
+EXPORT_SYMBOL(vcc_process_recv_queue);
+
+void atm_dev_signal_change(struct atm_dev *dev, char signal)
+{
+	pr_debug("%s signal=%d dev=%p number=%d dev->signal=%d\n",
+		__func__, signal, dev, dev->number, dev->signal);
+
+	/* atm driver sending invalid signal */
+	WARN_ON(signal < ATM_PHY_SIG_LOST || signal > ATM_PHY_SIG_FOUND);
+
+	if (dev->signal == signal)
+		return; /* no change */
+
+	dev->signal = signal;
+
+	atomic_notifier_call_chain(&atm_dev_notify_chain, signal, dev);
+}
+EXPORT_SYMBOL(atm_dev_signal_change);
+
+void atm_dev_release_vccs(struct atm_dev *dev)
+{
+	int i;
+
+	write_lock_irq(&vcc_sklist_lock);
+	for (i = 0; i < VCC_HTABLE_SIZE; i++) {
+		struct hlist_head *head = &vcc_hash[i];
+		struct hlist_node *tmp;
+		struct sock *s;
+		struct atm_vcc *vcc;
+
+		sk_for_each_safe(s, tmp, head) {
+			vcc = atm_sk(s);
+			if (vcc->dev == dev) {
+				vcc_release_async(vcc, -EPIPE);
+				sk_del_node_init(s);
+			}
+		}
+	}
+	write_unlock_irq(&vcc_sklist_lock);
+}
+EXPORT_SYMBOL(atm_dev_release_vccs);
+
+static int adjust_tp(struct atm_trafprm *tp, unsigned char aal)
+{
+	int max_sdu;
+
+	if (!tp->traffic_class)
+		return 0;
+	switch (aal) {
+	case ATM_AAL0:
+		max_sdu = ATM_CELL_SIZE-1;
+		break;
+	default:
+		pr_warn("AAL problems ... (%d)\n", aal);
+		fallthrough;
+	case ATM_AAL5:
+		max_sdu = ATM_MAX_AAL5_PDU;
+	}
+	if (!tp->max_sdu)
+		tp->max_sdu = max_sdu;
+	else if (tp->max_sdu > max_sdu)
+		return -EINVAL;
+	if (!tp->max_cdv)
+		tp->max_cdv = ATM_MAX_CDV;
+	return 0;
+}
+
+static int check_ci(const struct atm_vcc *vcc, short vpi, int vci)
+{
+	struct hlist_head *head = &vcc_hash[vci & (VCC_HTABLE_SIZE - 1)];
+	struct sock *s;
+	struct atm_vcc *walk;
+
+	sk_for_each(s, head) {
+		walk = atm_sk(s);
+		if (walk->dev != vcc->dev)
+			continue;
+		if (test_bit(ATM_VF_ADDR, &walk->flags) && walk->vpi == vpi &&
+		    walk->vci == vci && ((walk->qos.txtp.traffic_class !=
+		    ATM_NONE && vcc->qos.txtp.traffic_class != ATM_NONE) ||
+		    (walk->qos.rxtp.traffic_class != ATM_NONE &&
+		    vcc->qos.rxtp.traffic_class != ATM_NONE)))
+			return -EADDRINUSE;
+	}
+
+	/* allow VCCs with same VPI/VCI iff they don't collide on
+	   TX/RX (but we may refuse such sharing for other reasons,
+	   e.g. if protocol requires to have both channels) */
+
+	return 0;
+}
+
+static int find_ci(const struct atm_vcc *vcc, short *vpi, int *vci)
+{
+	static short p;        /* poor man's per-device cache */
+	static int c;
+	short old_p;
+	int old_c;
+	int err;
+
+	if (*vpi != ATM_VPI_ANY && *vci != ATM_VCI_ANY) {
+		err = check_ci(vcc, *vpi, *vci);
+		return err;
+	}
+	/* last scan may have left values out of bounds for current device */
+	if (*vpi != ATM_VPI_ANY)
+		p = *vpi;
+	else if (p >= 1 << vcc->dev->ci_range.vpi_bits)
+		p = 0;
+	if (*vci != ATM_VCI_ANY)
+		c = *vci;
+	else if (c < ATM_NOT_RSV_VCI || c >= 1 << vcc->dev->ci_range.vci_bits)
+			c = ATM_NOT_RSV_VCI;
+	old_p = p;
+	old_c = c;
+	do {
+		if (!check_ci(vcc, p, c)) {
+			*vpi = p;
+			*vci = c;
+			return 0;
+		}
+		if (*vci == ATM_VCI_ANY) {
+			c++;
+			if (c >= 1 << vcc->dev->ci_range.vci_bits)
+				c = ATM_NOT_RSV_VCI;
+		}
+		if ((c == ATM_NOT_RSV_VCI || *vci != ATM_VCI_ANY) &&
+		    *vpi == ATM_VPI_ANY) {
+			p++;
+			if (p >= 1 << vcc->dev->ci_range.vpi_bits)
+				p = 0;
+		}
+	} while (old_p != p || old_c != c);
+	return -EADDRINUSE;
+}
+
+static int __vcc_connect(struct atm_vcc *vcc, struct atm_dev *dev, short vpi,
+			 int vci)
+{
+	struct sock *sk = sk_atm(vcc);
+	int error;
+
+	if ((vpi != ATM_VPI_UNSPEC && vpi != ATM_VPI_ANY &&
+	    vpi >> dev->ci_range.vpi_bits) || (vci != ATM_VCI_UNSPEC &&
+	    vci != ATM_VCI_ANY && vci >> dev->ci_range.vci_bits))
+		return -EINVAL;
+	if (vci > 0 && vci < ATM_NOT_RSV_VCI && !capable(CAP_NET_BIND_SERVICE))
+		return -EPERM;
+	error = -ENODEV;
+	if (!try_module_get(dev->ops->owner))
+		return error;
+	vcc->dev = dev;
+	write_lock_irq(&vcc_sklist_lock);
+	if (test_bit(ATM_DF_REMOVED, &dev->flags) ||
+	    (error = find_ci(vcc, &vpi, &vci))) {
+		write_unlock_irq(&vcc_sklist_lock);
+		goto fail_module_put;
+	}
+	vcc->vpi = vpi;
+	vcc->vci = vci;
+	__vcc_insert_socket(sk);
+	write_unlock_irq(&vcc_sklist_lock);
+	switch (vcc->qos.aal) {
+	case ATM_AAL0:
+		error = atm_init_aal0(vcc);
+		vcc->stats = &dev->stats.aal0;
+		break;
+	case ATM_NO_AAL:
+		/* ATM_AAL5 is also used in the "0 for default" case */
+		vcc->qos.aal = ATM_AAL5;
+		fallthrough;
+	case ATM_AAL5:
+		error = atm_init_aal5(vcc);
+		vcc->stats = &dev->stats.aal5;
+		break;
+	default:
+		error = -EPROTOTYPE;
+	}
+	if (!error)
+		error = adjust_tp(&vcc->qos.txtp, vcc->qos.aal);
+	if (!error)
+		error = adjust_tp(&vcc->qos.rxtp, vcc->qos.aal);
+	if (error)
+		goto fail;
+	pr_debug("VCC %d.%d, AAL %d\n", vpi, vci, vcc->qos.aal);
+	pr_debug("  TX: %d, PCR %d..%d, SDU %d\n",
+		 vcc->qos.txtp.traffic_class,
+		 vcc->qos.txtp.min_pcr,
+		 vcc->qos.txtp.max_pcr,
+		 vcc->qos.txtp.max_sdu);
+	pr_debug("  RX: %d, PCR %d..%d, SDU %d\n",
+		 vcc->qos.rxtp.traffic_class,
+		 vcc->qos.rxtp.min_pcr,
+		 vcc->qos.rxtp.max_pcr,
+		 vcc->qos.rxtp.max_sdu);
+
+	if (dev->ops->open) {
+		error = dev->ops->open(vcc);
+		if (error)
+			goto fail;
+	}
+	return 0;
+
+fail:
+	vcc_remove_socket(sk);
+fail_module_put:
+	module_put(dev->ops->owner);
+	/* ensure we get dev module ref count correct */
+	vcc->dev = NULL;
+	return error;
+}
+
+int vcc_connect(struct socket *sock, int itf, short vpi, int vci)
+{
+	struct atm_dev *dev;
+	struct atm_vcc *vcc = ATM_SD(sock);
+	int error;
+
+	pr_debug("(vpi %d, vci %d)\n", vpi, vci);
+	if (sock->state == SS_CONNECTED)
+		return -EISCONN;
+	if (sock->state != SS_UNCONNECTED)
+		return -EINVAL;
+	if (!(vpi || vci))
+		return -EINVAL;
+
+	if (vpi != ATM_VPI_UNSPEC && vci != ATM_VCI_UNSPEC)
+		clear_bit(ATM_VF_PARTIAL, &vcc->flags);
+	else
+		if (test_bit(ATM_VF_PARTIAL, &vcc->flags))
+			return -EINVAL;
+	pr_debug("(TX: cl %d,bw %d-%d,sdu %d; "
+		 "RX: cl %d,bw %d-%d,sdu %d,AAL %s%d)\n",
+		 vcc->qos.txtp.traffic_class, vcc->qos.txtp.min_pcr,
+		 vcc->qos.txtp.max_pcr, vcc->qos.txtp.max_sdu,
+		 vcc->qos.rxtp.traffic_class, vcc->qos.rxtp.min_pcr,
+		 vcc->qos.rxtp.max_pcr, vcc->qos.rxtp.max_sdu,
+		 vcc->qos.aal == ATM_AAL5 ? "" :
+		 vcc->qos.aal == ATM_AAL0 ? "" : " ??? code ",
+		 vcc->qos.aal == ATM_AAL0 ? 0 : vcc->qos.aal);
+	if (!test_bit(ATM_VF_HASQOS, &vcc->flags))
+		return -EBADFD;
+	if (vcc->qos.txtp.traffic_class == ATM_ANYCLASS ||
+	    vcc->qos.rxtp.traffic_class == ATM_ANYCLASS)
+		return -EINVAL;
+	if (likely(itf != ATM_ITF_ANY)) {
+		dev = try_then_request_module(atm_dev_lookup(itf),
+					      "atm-device-%d", itf);
+	} else {
+		dev = NULL;
+		mutex_lock(&atm_dev_mutex);
+		if (!list_empty(&atm_devs)) {
+			dev = list_entry(atm_devs.next,
+					 struct atm_dev, dev_list);
+			atm_dev_hold(dev);
+		}
+		mutex_unlock(&atm_dev_mutex);
+	}
+	if (!dev)
+		return -ENODEV;
+	error = __vcc_connect(vcc, dev, vpi, vci);
+	if (error) {
+		atm_dev_put(dev);
+		return error;
+	}
+	if (vpi == ATM_VPI_UNSPEC || vci == ATM_VCI_UNSPEC)
+		set_bit(ATM_VF_PARTIAL, &vcc->flags);
+	if (test_bit(ATM_VF_READY, &ATM_SD(sock)->flags))
+		sock->state = SS_CONNECTED;
+	return 0;
+}
+
+int vcc_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
+		int flags)
+{
+	struct sock *sk = sock->sk;
+	struct atm_vcc *vcc;
+	struct sk_buff *skb;
+	int copied, error = -EINVAL;
+
+	if (sock->state != SS_CONNECTED)
+		return -ENOTCONN;
+
+	/* only handle MSG_DONTWAIT and MSG_PEEK */
+	if (flags & ~(MSG_DONTWAIT | MSG_PEEK))
+		return -EOPNOTSUPP;
+
+	vcc = ATM_SD(sock);
+	if (test_bit(ATM_VF_CLOSE, &vcc->flags) ||
+	    !test_bit(ATM_VF_READY, &vcc->flags))
+		return 0;
+
+	skb = skb_recv_datagram(sk, flags, &error);
+	if (!skb)
+		return error;
+
+	copied = skb->len;
+	if (copied > size) {
+		copied = size;
+		msg->msg_flags |= MSG_TRUNC;
+	}
+
+	error = skb_copy_datagram_msg(skb, 0, msg, copied);
+	if (error)
+		return error;
+	sock_recv_cmsgs(msg, sk, skb);
+
+	if (!(flags & MSG_PEEK)) {
+		pr_debug("%d -= %d\n", atomic_read(&sk->sk_rmem_alloc),
+			 skb->truesize);
+		atm_return(vcc, skb->truesize);
+	}
+
+	skb_free_datagram(sk, skb);
+	return copied;
+}
+
+int vcc_sendmsg(struct socket *sock, struct msghdr *m, size_t size)
+{
+	struct sock *sk = sock->sk;
+	DEFINE_WAIT(wait);
+	struct atm_vcc *vcc;
+	struct sk_buff *skb;
+	int eff, error;
+
+	lock_sock(sk);
+	if (sock->state != SS_CONNECTED) {
+		error = -ENOTCONN;
+		goto out;
+	}
+	if (m->msg_name) {
+		error = -EISCONN;
+		goto out;
+	}
+	vcc = ATM_SD(sock);
+	if (test_bit(ATM_VF_CLOSE, &vcc->flags) ||
+	    !test_bit(ATM_VF_READY, &vcc->flags)) {
+		error = -EPIPE;
+		send_sig(SIGPIPE, current, 0);
+		goto out;
+	}
+	if (!size) {
+		error = 0;
+		goto out;
+	}
+	if (size > vcc->qos.txtp.max_sdu) {
+		error = -EMSGSIZE;
+		goto out;
+	}
+
+	eff = (size+3) & ~3; /* align to word boundary */
+	prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+	error = 0;
+	while (!vcc_tx_ready(vcc, eff)) {
+		if (m->msg_flags & MSG_DONTWAIT) {
+			error = -EAGAIN;
+			break;
+		}
+		schedule();
+		if (signal_pending(current)) {
+			error = -ERESTARTSYS;
+			break;
+		}
+		if (test_bit(ATM_VF_CLOSE, &vcc->flags) ||
+		    !test_bit(ATM_VF_READY, &vcc->flags)) {
+			error = -EPIPE;
+			send_sig(SIGPIPE, current, 0);
+			break;
+		}
+		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+	}
+	finish_wait(sk_sleep(sk), &wait);
+	if (error)
+		goto out;
+
+	skb = alloc_skb(eff, GFP_KERNEL);
+	if (!skb) {
+		error = -ENOMEM;
+		goto out;
+	}
+	pr_debug("%d += %d\n", sk_wmem_alloc_get(sk), skb->truesize);
+	atm_account_tx(vcc, skb);
+
+	skb->dev = NULL; /* for paths shared with net_device interfaces */
+	if (!copy_from_iter_full(skb_put(skb, size), size, &m->msg_iter)) {
+		error = -EFAULT;
+		goto free_skb;
+	}
+	if (eff != size)
+		memset(skb->data + size, 0, eff-size);
+
+	error = vcc->dev->ops->send(vcc, skb);
+	error = error ? error : size;
+out:
+	release_sock(sk);
+	return error;
+free_skb:
+	atm_return_tx(vcc, skb);
+	kfree_skb(skb);
+	goto out;
+}
+
+__poll_t vcc_poll(struct file *file, struct socket *sock, poll_table *wait)
+{
+	struct sock *sk = sock->sk;
+	struct atm_vcc *vcc;
+	__poll_t mask;
+
+	sock_poll_wait(file, sock, wait);
+	mask = 0;
+
+	vcc = ATM_SD(sock);
+
+	/* exceptional events */
+	if (sk->sk_err)
+		mask = EPOLLERR;
+
+	if (test_bit(ATM_VF_CLOSE, &vcc->flags))
+		mask |= EPOLLHUP;
+
+	/* readable? */
+	if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
+		mask |= EPOLLIN | EPOLLRDNORM;
+
+	/* writable? */
+	if (vcc->qos.txtp.traffic_class != ATM_NONE &&
+	    vcc_writable(sk))
+		mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;
+
+	return mask;
+}
+
+static int check_tp(const struct atm_trafprm *tp)
+{
+	/* @@@ Should be merged with adjust_tp */
+	if (tp->traffic_class > ATM_ANYCLASS)
+		return -EINVAL;
+	if (!tp->traffic_class || tp->traffic_class == ATM_ANYCLASS)
+		return 0;
+	if (tp->traffic_class != ATM_UBR && !tp->min_pcr && !tp->pcr &&
+	    !tp->max_pcr)
+		return -EINVAL;
+	if (tp->min_pcr == ATM_MAX_PCR)
+		return -EINVAL;
+	if (tp->min_pcr && tp->max_pcr && tp->max_pcr != ATM_MAX_PCR &&
+	    tp->min_pcr > tp->max_pcr)
+		return -EINVAL;
+	/*
+	 * We allow pcr to be outside [min_pcr,max_pcr], because later
+	 * adjustment may still push it in the valid range.
+	 */
+	return 0;
+}
+
+static int check_qos(const struct atm_qos *qos)
+{
+	int error;
+
+	if (!qos->txtp.traffic_class && !qos->rxtp.traffic_class)
+		return -EINVAL;
+	if (qos->txtp.traffic_class != qos->rxtp.traffic_class &&
+	    qos->txtp.traffic_class && qos->rxtp.traffic_class &&
+	    qos->txtp.traffic_class != ATM_ANYCLASS &&
+	    qos->rxtp.traffic_class != ATM_ANYCLASS)
+		return -EINVAL;
+	error = check_tp(&qos->txtp);
+	if (error)
+		return error;
+	return check_tp(&qos->rxtp);
+}
+
+int vcc_setsockopt(struct socket *sock, int level, int optname,
+		   sockptr_t optval, unsigned int optlen)
+{
+	struct atm_vcc *vcc;
+	int value;
+	int error;
+
+	if (__SO_LEVEL_MATCH(optname, level) && optlen != __SO_SIZE(optname))
+		return -EINVAL;
+
+	vcc = ATM_SD(sock);
+	switch (optname) {
+	case SO_ATMQOS:
+	{
+		struct atm_qos qos;
+
+		error = copy_safe_from_sockptr(&qos, sizeof(qos), optval,
+					       optlen);
+		if (error)
+			return error;
+		error = check_qos(&qos);
+		if (error)
+			return error;
+		/* QoS cannot be renegotiated on an already connected VCC. */
+		if (sock->state == SS_CONNECTED)
+			return -EOPNOTSUPP;
+		if (sock->state != SS_UNCONNECTED)
+			return -EBADFD;
+		vcc->qos = qos;
+		set_bit(ATM_VF_HASQOS, &vcc->flags);
+		return 0;
+	}
+	case SO_SETCLP:
+		error = copy_safe_from_sockptr(&value, sizeof(value), optval,
+					       optlen);
+		if (error)
+			return error;
+		if (value)
+			vcc->atm_options |= ATM_ATMOPT_CLP;
+		else
+			vcc->atm_options &= ~ATM_ATMOPT_CLP;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+int vcc_getsockopt(struct socket *sock, int level, int optname,
+		   sockopt_t *opt)
+{
+	struct atm_vcc *vcc;
+	int val;
+	int len;
+
+	len = opt->optlen;
+	if (__SO_LEVEL_MATCH(optname, level) && len != __SO_SIZE(optname))
+		return -EINVAL;
+
+	vcc = ATM_SD(sock);
+	switch (optname) {
+	case SO_ATMQOS:
+		if (!test_bit(ATM_VF_HASQOS, &vcc->flags))
+			return -EINVAL;
+		return copy_to_iter(&vcc->qos, sizeof(vcc->qos),
+				    &opt->iter_out) != sizeof(vcc->qos)
+			? -EFAULT : 0;
+	case SO_SETCLP:
+		val = vcc->atm_options & ATM_ATMOPT_CLP ? 1 : 0;
+		return copy_to_iter(&val, sizeof(val), &opt->iter_out) !=
+		       sizeof(val) ? -EFAULT : 0;
+	case SO_ATMPVC:
+	{
+		struct sockaddr_atmpvc pvc;
+
+		if (!vcc->dev || !test_bit(ATM_VF_ADDR, &vcc->flags))
+			return -ENOTCONN;
+		memset(&pvc, 0, sizeof(pvc));
+		pvc.sap_family = AF_ATMPVC;
+		pvc.sap_addr.itf = vcc->dev->number;
+		pvc.sap_addr.vpi = vcc->vpi;
+		pvc.sap_addr.vci = vcc->vci;
+		return copy_to_iter(&pvc, sizeof(pvc), &opt->iter_out) !=
+		       sizeof(pvc) ? -EFAULT : 0;
+	}
+	default:
+		return -EINVAL;
+	}
+}
+
+int register_atmdevice_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&atm_dev_notify_chain, nb);
+}
+EXPORT_SYMBOL_GPL(register_atmdevice_notifier);
+
+void unregister_atmdevice_notifier(struct notifier_block *nb)
+{
+	atomic_notifier_chain_unregister(&atm_dev_notify_chain, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_atmdevice_notifier);
+
+static int __init atm_init(void)
+{
+	int error;
+
+	error = proto_register(&vcc_proto, 0);
+	if (error < 0)
+		goto out;
+	error = atmpvc_init();
+	if (error < 0) {
+		pr_err("atmpvc_init() failed with %d\n", error);
+		goto out_unregister_vcc_proto;
+	}
+	error = atm_proc_init();
+	if (error < 0) {
+		pr_err("atm_proc_init() failed with %d\n", error);
+		goto out_atmpvc_exit;
+	}
+	error = atm_sysfs_init();
+	if (error < 0) {
+		pr_err("atm_sysfs_init() failed with %d\n", error);
+		goto out_atmproc_exit;
+	}
+out:
+	return error;
+out_atmproc_exit:
+	atm_proc_exit();
+out_atmpvc_exit:
+	atmpvc_exit();
+out_unregister_vcc_proto:
+	proto_unregister(&vcc_proto);
+	goto out;
+}
+
+static void __exit atm_exit(void)
+{
+	atm_proc_exit();
+	atm_sysfs_exit();
+	atmpvc_exit();
+	proto_unregister(&vcc_proto);
+}
+
+subsys_initcall(atm_init);
+
+module_exit(atm_exit);
+
+MODULE_DESCRIPTION("Asynchronous Transfer Mode (ATM) networking core");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_NETPROTO(PF_ATMPVC);