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, 844 insertions, 0 deletions

diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c
new file mode 100644
index 000000000..ca89fe967
--- /dev/null
+++ b/net/nfc/llcp_commands.c
@@ -0,0 +1,844 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2011  Intel Corporation. All rights reserved.
+ */
+
+#define pr_fmt(fmt) "llcp: %s: " fmt, __func__
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/nfc.h>
+
+#include <net/nfc/nfc.h>
+
+#include "nfc.h"
+#include "llcp.h"
+
+static const u8 llcp_tlv_length[LLCP_TLV_MAX] = {
+	0,
+	1, /* VERSION */
+	2, /* MIUX */
+	2, /* WKS */
+	1, /* LTO */
+	1, /* RW */
+	0, /* SN */
+	1, /* OPT */
+	0, /* SDREQ */
+	2, /* SDRES */
+
+};
+
+static u8 llcp_tlv8(const u8 *tlv, u8 type)
+{
+	if (tlv[0] != type || tlv[1] != llcp_tlv_length[tlv[0]])
+		return 0;
+
+	return tlv[2];
+}
+
+static u16 llcp_tlv16(const u8 *tlv, u8 type)
+{
+	if (tlv[0] != type || tlv[1] != llcp_tlv_length[tlv[0]])
+		return 0;
+
+	return be16_to_cpu(*((__be16 *)(tlv + 2)));
+}
+
+
+static u8 llcp_tlv_version(const u8 *tlv)
+{
+	return llcp_tlv8(tlv, LLCP_TLV_VERSION);
+}
+
+static u16 llcp_tlv_miux(const u8 *tlv)
+{
+	return llcp_tlv16(tlv, LLCP_TLV_MIUX) & 0x7ff;
+}
+
+static u16 llcp_tlv_wks(const u8 *tlv)
+{
+	return llcp_tlv16(tlv, LLCP_TLV_WKS);
+}
+
+static u16 llcp_tlv_lto(const u8 *tlv)
+{
+	return llcp_tlv8(tlv, LLCP_TLV_LTO);
+}
+
+static u8 llcp_tlv_opt(const u8 *tlv)
+{
+	return llcp_tlv8(tlv, LLCP_TLV_OPT);
+}
+
+static u8 llcp_tlv_rw(const u8 *tlv)
+{
+	return llcp_tlv8(tlv, LLCP_TLV_RW) & 0xf;
+}
+
+u8 *nfc_llcp_build_tlv(u8 type, const u8 *value, u8 value_length, u8 *tlv_length)
+{
+	u8 *tlv, length;
+
+	pr_debug("type %d\n", type);
+
+	if (type >= LLCP_TLV_MAX)
+		return NULL;
+
+	length = llcp_tlv_length[type];
+	if (length == 0 && value_length == 0)
+		return NULL;
+	else if (length == 0)
+		length = value_length;
+
+	*tlv_length = 2 + length;
+	tlv = kzalloc(2 + length, GFP_KERNEL);
+	if (tlv == NULL)
+		return tlv;
+
+	tlv[0] = type;
+	tlv[1] = length;
+	memcpy(tlv + 2, value, length);
+
+	return tlv;
+}
+
+struct nfc_llcp_sdp_tlv *nfc_llcp_build_sdres_tlv(u8 tid, u8 sap)
+{
+	struct nfc_llcp_sdp_tlv *sdres;
+	u8 value[2];
+
+	sdres = kzalloc_obj(struct nfc_llcp_sdp_tlv);
+	if (sdres == NULL)
+		return NULL;
+
+	value[0] = tid;
+	value[1] = sap;
+
+	sdres->tlv = nfc_llcp_build_tlv(LLCP_TLV_SDRES, value, 2,
+					&sdres->tlv_len);
+	if (sdres->tlv == NULL) {
+		kfree(sdres);
+		return NULL;
+	}
+
+	sdres->tid = tid;
+	sdres->sap = sap;
+
+	INIT_HLIST_NODE(&sdres->node);
+
+	return sdres;
+}
+
+struct nfc_llcp_sdp_tlv *nfc_llcp_build_sdreq_tlv(u8 tid, const char *uri,
+						  size_t uri_len)
+{
+	struct nfc_llcp_sdp_tlv *sdreq;
+
+	pr_debug("uri: %s, len: %zu\n", uri, uri_len);
+
+	/* sdreq->tlv_len is u8, takes uri_len, + 3 for header, + 1 for NULL */
+	if (WARN_ON_ONCE(uri_len > U8_MAX - 4))
+		return NULL;
+
+	sdreq = kzalloc_obj(struct nfc_llcp_sdp_tlv);
+	if (sdreq == NULL)
+		return NULL;
+
+	sdreq->tlv_len = uri_len + 3;
+
+	if (uri[uri_len - 1] == 0)
+		sdreq->tlv_len--;
+
+	sdreq->tlv = kzalloc(sdreq->tlv_len + 1, GFP_KERNEL);
+	if (sdreq->tlv == NULL) {
+		kfree(sdreq);
+		return NULL;
+	}
+
+	sdreq->tlv[0] = LLCP_TLV_SDREQ;
+	sdreq->tlv[1] = sdreq->tlv_len - 2;
+	sdreq->tlv[2] = tid;
+
+	sdreq->tid = tid;
+	sdreq->uri = sdreq->tlv + 3;
+	memcpy(sdreq->uri, uri, uri_len);
+
+	sdreq->time = jiffies;
+
+	INIT_HLIST_NODE(&sdreq->node);
+
+	return sdreq;
+}
+
+void nfc_llcp_free_sdp_tlv(struct nfc_llcp_sdp_tlv *sdp)
+{
+	kfree(sdp->tlv);
+	kfree(sdp);
+}
+
+void nfc_llcp_free_sdp_tlv_list(struct hlist_head *head)
+{
+	struct nfc_llcp_sdp_tlv *sdp;
+	struct hlist_node *n;
+
+	hlist_for_each_entry_safe(sdp, n, head, node) {
+		hlist_del(&sdp->node);
+
+		nfc_llcp_free_sdp_tlv(sdp);
+	}
+}
+
+int nfc_llcp_parse_gb_tlv(struct nfc_llcp_local *local,
+			  const u8 *tlv_array, u16 tlv_array_len)
+{
+	const u8 *tlv = tlv_array;
+	u8 type, length;
+	u16 offset = 0;
+
+	pr_debug("TLV array length %d\n", tlv_array_len);
+
+	if (local == NULL)
+		return -ENODEV;
+
+	while (offset < tlv_array_len) {
+		if (offset + 2 > tlv_array_len)
+			return -EINVAL;
+
+		type = tlv[0];
+		length = tlv[1];
+
+		if (offset + 2 + length > tlv_array_len)
+			return -EINVAL;
+
+		pr_debug("type 0x%x length %d\n", type, length);
+
+		switch (type) {
+		case LLCP_TLV_VERSION:
+			local->remote_version = llcp_tlv_version(tlv);
+			break;
+		case LLCP_TLV_MIUX:
+			local->remote_miu = llcp_tlv_miux(tlv) + 128;
+			break;
+		case LLCP_TLV_WKS:
+			local->remote_wks = llcp_tlv_wks(tlv);
+			break;
+		case LLCP_TLV_LTO:
+			local->remote_lto = llcp_tlv_lto(tlv) * 10;
+			break;
+		case LLCP_TLV_OPT:
+			local->remote_opt = llcp_tlv_opt(tlv);
+			break;
+		default:
+			pr_err("Invalid gt tlv value 0x%x\n", type);
+			break;
+		}
+
+		offset += length + 2;
+		tlv += length + 2;
+	}
+
+	pr_debug("version 0x%x miu %d lto %d opt 0x%x wks 0x%x\n",
+		 local->remote_version, local->remote_miu,
+		 local->remote_lto, local->remote_opt,
+		 local->remote_wks);
+
+	return 0;
+}
+
+int nfc_llcp_parse_connection_tlv(struct nfc_llcp_sock *sock,
+				  const u8 *tlv_array, u16 tlv_array_len)
+{
+	const u8 *tlv = tlv_array;
+	u8 type, length;
+	u16 offset = 0;
+
+	pr_debug("TLV array length %d\n", tlv_array_len);
+
+	if (sock == NULL)
+		return -ENOTCONN;
+
+	while (offset < tlv_array_len) {
+		if (offset + 2 > tlv_array_len)
+			return -EINVAL;
+
+		type = tlv[0];
+		length = tlv[1];
+
+		if (offset + 2 + length > tlv_array_len)
+			return -EINVAL;
+
+		pr_debug("type 0x%x length %d\n", type, length);
+
+		switch (type) {
+		case LLCP_TLV_MIUX:
+			sock->remote_miu = llcp_tlv_miux(tlv) + 128;
+			break;
+		case LLCP_TLV_RW:
+			sock->remote_rw = llcp_tlv_rw(tlv);
+			break;
+		case LLCP_TLV_SN:
+			break;
+		default:
+			pr_err("Invalid gt tlv value 0x%x\n", type);
+			break;
+		}
+
+		offset += length + 2;
+		tlv += length + 2;
+	}
+
+	pr_debug("sock %p rw %d miu %d\n", sock,
+		 sock->remote_rw, sock->remote_miu);
+
+	return 0;
+}
+
+static struct sk_buff *llcp_add_header(struct sk_buff *pdu,
+				       u8 dsap, u8 ssap, u8 ptype)
+{
+	u8 header[2];
+
+	pr_debug("ptype 0x%x dsap 0x%x ssap 0x%x\n", ptype, dsap, ssap);
+
+	header[0] = (u8)((dsap << 2) | (ptype >> 2));
+	header[1] = (u8)((ptype << 6) | ssap);
+
+	pr_debug("header 0x%x 0x%x\n", header[0], header[1]);
+
+	skb_put_data(pdu, header, LLCP_HEADER_SIZE);
+
+	return pdu;
+}
+
+static struct sk_buff *llcp_add_tlv(struct sk_buff *pdu, const u8 *tlv,
+				    u8 tlv_length)
+{
+	/* XXX Add an skb length check */
+
+	if (tlv == NULL)
+		return NULL;
+
+	skb_put_data(pdu, tlv, tlv_length);
+
+	return pdu;
+}
+
+static struct sk_buff *llcp_allocate_pdu(struct nfc_llcp_sock *sock,
+					 u8 cmd, u16 size)
+{
+	struct sk_buff *skb;
+	int err;
+
+	if (sock->ssap == 0)
+		return NULL;
+
+	skb = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT,
+				 size + LLCP_HEADER_SIZE, &err);
+	if (skb == NULL) {
+		pr_err("Could not allocate PDU\n");
+		return NULL;
+	}
+
+	skb = llcp_add_header(skb, sock->dsap, sock->ssap, cmd);
+
+	return skb;
+}
+
+int nfc_llcp_send_disconnect(struct nfc_llcp_sock *sock)
+{
+	struct sk_buff *skb;
+	struct nfc_dev *dev;
+	struct nfc_llcp_local *local;
+
+	local = sock->local;
+	if (local == NULL)
+		return -ENODEV;
+
+	dev = sock->dev;
+	if (dev == NULL)
+		return -ENODEV;
+
+	skb = llcp_allocate_pdu(sock, LLCP_PDU_DISC, 0);
+	if (skb == NULL)
+		return -ENOMEM;
+
+	skb_queue_tail(&local->tx_queue, skb);
+
+	return 0;
+}
+
+int nfc_llcp_send_symm(struct nfc_dev *dev)
+{
+	struct sk_buff *skb;
+	struct nfc_llcp_local *local;
+	u16 size = 0;
+	int err;
+
+	local = nfc_llcp_find_local(dev);
+	if (local == NULL)
+		return -ENODEV;
+
+	size += LLCP_HEADER_SIZE;
+	size += dev->tx_headroom + dev->tx_tailroom + NFC_HEADER_SIZE;
+
+	skb = alloc_skb(size, GFP_KERNEL);
+	if (skb == NULL) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	skb_reserve(skb, dev->tx_headroom + NFC_HEADER_SIZE);
+
+	skb = llcp_add_header(skb, 0, 0, LLCP_PDU_SYMM);
+
+	__net_timestamp(skb);
+
+	nfc_llcp_send_to_raw_sock(local, skb, NFC_DIRECTION_TX);
+
+	err = nfc_data_exchange(dev, local->target_idx, skb,
+				 nfc_llcp_recv, local);
+out:
+	nfc_llcp_local_put(local);
+	return err;
+}
+
+int nfc_llcp_send_connect(struct nfc_llcp_sock *sock)
+{
+	struct nfc_llcp_local *local;
+	struct sk_buff *skb;
+	const u8 *service_name_tlv = NULL;
+	const u8 *miux_tlv = NULL;
+	const u8 *rw_tlv = NULL;
+	u8 service_name_tlv_length = 0;
+	u8 miux_tlv_length,  rw_tlv_length, rw;
+	int err;
+	u16 size = 0;
+	__be16 miux;
+
+	local = sock->local;
+	if (local == NULL)
+		return -ENODEV;
+
+	if (sock->service_name != NULL) {
+		service_name_tlv = nfc_llcp_build_tlv(LLCP_TLV_SN,
+						      sock->service_name,
+						      sock->service_name_len,
+						      &service_name_tlv_length);
+		if (!service_name_tlv) {
+			err = -ENOMEM;
+			goto error_tlv;
+		}
+		size += service_name_tlv_length;
+	}
+
+	/* If the socket parameters are not set, use the local ones */
+	miux = be16_to_cpu(sock->miux) > LLCP_MAX_MIUX ?
+		local->miux : sock->miux;
+	rw = sock->rw > LLCP_MAX_RW ? local->rw : sock->rw;
+
+	miux_tlv = nfc_llcp_build_tlv(LLCP_TLV_MIUX, (u8 *)&miux, 0,
+				      &miux_tlv_length);
+	if (!miux_tlv) {
+		err = -ENOMEM;
+		goto error_tlv;
+	}
+	size += miux_tlv_length;
+
+	rw_tlv = nfc_llcp_build_tlv(LLCP_TLV_RW, &rw, 0, &rw_tlv_length);
+	if (!rw_tlv) {
+		err = -ENOMEM;
+		goto error_tlv;
+	}
+	size += rw_tlv_length;
+
+	pr_debug("SKB size %d SN length %zu\n", size, sock->service_name_len);
+
+	skb = llcp_allocate_pdu(sock, LLCP_PDU_CONNECT, size);
+	if (skb == NULL) {
+		err = -ENOMEM;
+		goto error_tlv;
+	}
+
+	llcp_add_tlv(skb, service_name_tlv, service_name_tlv_length);
+	llcp_add_tlv(skb, miux_tlv, miux_tlv_length);
+	llcp_add_tlv(skb, rw_tlv, rw_tlv_length);
+
+	skb_queue_tail(&local->tx_queue, skb);
+
+	err = 0;
+
+error_tlv:
+	if (err)
+		pr_err("error %d\n", err);
+
+	kfree(service_name_tlv);
+	kfree(miux_tlv);
+	kfree(rw_tlv);
+
+	return err;
+}
+
+int nfc_llcp_send_cc(struct nfc_llcp_sock *sock)
+{
+	struct nfc_llcp_local *local;
+	struct sk_buff *skb;
+	const u8 *miux_tlv = NULL;
+	const u8 *rw_tlv = NULL;
+	u8 miux_tlv_length, rw_tlv_length, rw;
+	int err;
+	u16 size = 0;
+	__be16 miux;
+
+	local = sock->local;
+	if (local == NULL)
+		return -ENODEV;
+
+	/* If the socket parameters are not set, use the local ones */
+	miux = be16_to_cpu(sock->miux) > LLCP_MAX_MIUX ?
+		local->miux : sock->miux;
+	rw = sock->rw > LLCP_MAX_RW ? local->rw : sock->rw;
+
+	miux_tlv = nfc_llcp_build_tlv(LLCP_TLV_MIUX, (u8 *)&miux, 0,
+				      &miux_tlv_length);
+	if (!miux_tlv) {
+		err = -ENOMEM;
+		goto error_tlv;
+	}
+	size += miux_tlv_length;
+
+	rw_tlv = nfc_llcp_build_tlv(LLCP_TLV_RW, &rw, 0, &rw_tlv_length);
+	if (!rw_tlv) {
+		err = -ENOMEM;
+		goto error_tlv;
+	}
+	size += rw_tlv_length;
+
+	skb = llcp_allocate_pdu(sock, LLCP_PDU_CC, size);
+	if (skb == NULL) {
+		err = -ENOMEM;
+		goto error_tlv;
+	}
+
+	llcp_add_tlv(skb, miux_tlv, miux_tlv_length);
+	llcp_add_tlv(skb, rw_tlv, rw_tlv_length);
+
+	skb_queue_tail(&local->tx_queue, skb);
+
+	err = 0;
+
+error_tlv:
+	if (err)
+		pr_err("error %d\n", err);
+
+	kfree(miux_tlv);
+	kfree(rw_tlv);
+
+	return err;
+}
+
+static struct sk_buff *nfc_llcp_allocate_snl(struct nfc_llcp_local *local,
+					     size_t tlv_length)
+{
+	struct sk_buff *skb;
+	struct nfc_dev *dev;
+	u16 size = 0;
+
+	if (local == NULL)
+		return ERR_PTR(-ENODEV);
+
+	dev = local->dev;
+	if (dev == NULL)
+		return ERR_PTR(-ENODEV);
+
+	size += LLCP_HEADER_SIZE;
+	size += dev->tx_headroom + dev->tx_tailroom + NFC_HEADER_SIZE;
+	size += tlv_length;
+
+	skb = alloc_skb(size, GFP_KERNEL);
+	if (skb == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	skb_reserve(skb, dev->tx_headroom + NFC_HEADER_SIZE);
+
+	skb = llcp_add_header(skb, LLCP_SAP_SDP, LLCP_SAP_SDP, LLCP_PDU_SNL);
+
+	return skb;
+}
+
+int nfc_llcp_send_snl_sdres(struct nfc_llcp_local *local,
+			    struct hlist_head *tlv_list, size_t tlvs_len)
+{
+	struct nfc_llcp_sdp_tlv *sdp;
+	struct hlist_node *n;
+	struct sk_buff *skb;
+
+	skb = nfc_llcp_allocate_snl(local, tlvs_len);
+	if (IS_ERR(skb))
+		return PTR_ERR(skb);
+
+	hlist_for_each_entry_safe(sdp, n, tlv_list, node) {
+		skb_put_data(skb, sdp->tlv, sdp->tlv_len);
+
+		hlist_del(&sdp->node);
+
+		nfc_llcp_free_sdp_tlv(sdp);
+	}
+
+	skb_queue_tail(&local->tx_queue, skb);
+
+	return 0;
+}
+
+int nfc_llcp_send_snl_sdreq(struct nfc_llcp_local *local,
+			    struct hlist_head *tlv_list, size_t tlvs_len)
+{
+	struct nfc_llcp_sdp_tlv *sdreq;
+	struct hlist_node *n;
+	struct sk_buff *skb;
+
+	skb = nfc_llcp_allocate_snl(local, tlvs_len);
+	if (IS_ERR(skb))
+		return PTR_ERR(skb);
+
+	mutex_lock(&local->sdreq_lock);
+
+	if (hlist_empty(&local->pending_sdreqs))
+		mod_timer(&local->sdreq_timer,
+			  jiffies + msecs_to_jiffies(3 * local->remote_lto));
+
+	hlist_for_each_entry_safe(sdreq, n, tlv_list, node) {
+		pr_debug("tid %d for %s\n", sdreq->tid, sdreq->uri);
+
+		skb_put_data(skb, sdreq->tlv, sdreq->tlv_len);
+
+		hlist_del(&sdreq->node);
+
+		hlist_add_head(&sdreq->node, &local->pending_sdreqs);
+	}
+
+	mutex_unlock(&local->sdreq_lock);
+
+	skb_queue_tail(&local->tx_queue, skb);
+
+	return 0;
+}
+
+int nfc_llcp_send_dm(struct nfc_llcp_local *local, u8 ssap, u8 dsap, u8 reason)
+{
+	struct sk_buff *skb;
+	struct nfc_dev *dev;
+	u16 size = 1; /* Reason code */
+
+	pr_debug("Sending DM reason 0x%x\n", reason);
+
+	if (local == NULL)
+		return -ENODEV;
+
+	dev = local->dev;
+	if (dev == NULL)
+		return -ENODEV;
+
+	size += LLCP_HEADER_SIZE;
+	size += dev->tx_headroom + dev->tx_tailroom + NFC_HEADER_SIZE;
+
+	skb = alloc_skb(size, GFP_KERNEL);
+	if (skb == NULL)
+		return -ENOMEM;
+
+	skb_reserve(skb, dev->tx_headroom + NFC_HEADER_SIZE);
+
+	skb = llcp_add_header(skb, dsap, ssap, LLCP_PDU_DM);
+
+	skb_put_data(skb, &reason, 1);
+
+	skb_queue_head(&local->tx_queue, skb);
+
+	return 0;
+}
+
+int nfc_llcp_send_i_frame(struct nfc_llcp_sock *sock,
+			  struct msghdr *msg, size_t len)
+{
+	struct sk_buff *pdu;
+	struct sock *sk = &sock->sk;
+	struct nfc_llcp_local *local;
+	size_t frag_len = 0, remaining_len;
+	u8 *msg_data, *msg_ptr;
+	u16 remote_miu;
+
+	pr_debug("Send I frame len %zd\n", len);
+
+	local = sock->local;
+	if (local == NULL)
+		return -ENODEV;
+
+	/* Remote is ready but has not acknowledged our frames */
+	if((sock->remote_ready &&
+	    skb_queue_len(&sock->tx_pending_queue) >= sock->remote_rw &&
+	    skb_queue_len(&sock->tx_queue) >= 2 * sock->remote_rw)) {
+		pr_err("Pending queue is full %d frames\n",
+		       skb_queue_len(&sock->tx_pending_queue));
+		return -ENOBUFS;
+	}
+
+	/* Remote is not ready and we've been queueing enough frames */
+	if ((!sock->remote_ready &&
+	     skb_queue_len(&sock->tx_queue) >= 2 * sock->remote_rw)) {
+		pr_err("Tx queue is full %d frames\n",
+		       skb_queue_len(&sock->tx_queue));
+		return -ENOBUFS;
+	}
+
+	msg_data = kmalloc(len, GFP_USER | __GFP_NOWARN);
+	if (msg_data == NULL)
+		return -ENOMEM;
+
+	if (memcpy_from_msg(msg_data, msg, len)) {
+		kfree(msg_data);
+		return -EFAULT;
+	}
+
+	remaining_len = len;
+	msg_ptr = msg_data;
+
+	do {
+		remote_miu = sock->remote_miu > LLCP_MAX_MIU ?
+				LLCP_DEFAULT_MIU : sock->remote_miu;
+
+		frag_len = min_t(size_t, remote_miu, remaining_len);
+
+		pr_debug("Fragment %zd bytes remaining %zd",
+			 frag_len, remaining_len);
+
+		pdu = llcp_allocate_pdu(sock, LLCP_PDU_I,
+					frag_len + LLCP_SEQUENCE_SIZE);
+		if (pdu == NULL) {
+			kfree(msg_data);
+			return -ENOMEM;
+		}
+
+		skb_put(pdu, LLCP_SEQUENCE_SIZE);
+
+		if (likely(frag_len > 0))
+			skb_put_data(pdu, msg_ptr, frag_len);
+
+		skb_queue_tail(&sock->tx_queue, pdu);
+
+		lock_sock(sk);
+
+		nfc_llcp_queue_i_frames(sock);
+
+		release_sock(sk);
+
+		remaining_len -= frag_len;
+		msg_ptr += frag_len;
+	} while (remaining_len > 0);
+
+	kfree(msg_data);
+
+	return len;
+}
+
+int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap,
+			   struct msghdr *msg, size_t len)
+{
+	struct sk_buff *pdu;
+	struct nfc_llcp_local *local;
+	size_t frag_len = 0, remaining_len;
+	u8 *msg_ptr, *msg_data;
+	u16 remote_miu;
+	int err;
+
+	pr_debug("Send UI frame len %zd\n", len);
+
+	local = sock->local;
+	if (local == NULL)
+		return -ENODEV;
+
+	msg_data = kmalloc(len, GFP_USER | __GFP_NOWARN);
+	if (msg_data == NULL)
+		return -ENOMEM;
+
+	if (memcpy_from_msg(msg_data, msg, len)) {
+		kfree(msg_data);
+		return -EFAULT;
+	}
+
+	remaining_len = len;
+	msg_ptr = msg_data;
+
+	do {
+		remote_miu = sock->remote_miu > LLCP_MAX_MIU ?
+				local->remote_miu : sock->remote_miu;
+
+		frag_len = min_t(size_t, remote_miu, remaining_len);
+
+		pr_debug("Fragment %zd bytes remaining %zd",
+			 frag_len, remaining_len);
+
+		pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, 0,
+					 frag_len + LLCP_HEADER_SIZE, &err);
+		if (pdu == NULL) {
+			pr_err("Could not allocate PDU (error=%d)\n", err);
+			len -= remaining_len;
+			if (len == 0)
+				len = err;
+			break;
+		}
+
+		pdu = llcp_add_header(pdu, dsap, ssap, LLCP_PDU_UI);
+
+		if (likely(frag_len > 0))
+			skb_put_data(pdu, msg_ptr, frag_len);
+
+		spin_lock(&local->tx_queue.lock);
+
+		if (list_empty(&local->list)) {
+			spin_unlock(&local->tx_queue.lock);
+
+			kfree_skb(pdu);
+
+			len -= remaining_len;
+			if (len == 0)
+				len = -ENXIO;
+			break;
+		}
+
+		/* No need to check for the peer RW for UI frames */
+		__skb_queue_tail(&local->tx_queue, pdu);
+
+		spin_unlock(&local->tx_queue.lock);
+
+		remaining_len -= frag_len;
+		msg_ptr += frag_len;
+	} while (remaining_len > 0);
+
+	kfree(msg_data);
+
+	return len;
+}
+
+int nfc_llcp_send_rr(struct nfc_llcp_sock *sock)
+{
+	struct sk_buff *skb;
+	struct nfc_llcp_local *local;
+
+	pr_debug("Send rr nr %d\n", sock->recv_n);
+
+	local = sock->local;
+	if (local == NULL)
+		return -ENODEV;
+
+	skb = llcp_allocate_pdu(sock, LLCP_PDU_RR, LLCP_SEQUENCE_SIZE);
+	if (skb == NULL)
+		return -ENOMEM;
+
+	skb_put(skb, LLCP_SEQUENCE_SIZE);
+
+	skb->data[2] = sock->recv_n;
+
+	skb_queue_head(&local->tx_queue, skb);
+
+	return 0;
+}