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, 627 insertions, 0 deletions

diff --git a/net/devlink/linecard.c b/net/devlink/linecard.c
new file mode 100644
index 000000000..fd18f2759
--- /dev/null
+++ b/net/devlink/linecard.c
@@ -0,0 +1,627 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Jiri Pirko <jiri@mellanox.com>
+ */
+
+#include "devl_internal.h"
+
+struct devlink_linecard {
+	struct list_head list;
+	struct devlink *devlink;
+	unsigned int index;
+	const struct devlink_linecard_ops *ops;
+	void *priv;
+	enum devlink_linecard_state state;
+	struct mutex state_lock; /* Protects state */
+	const char *type;
+	struct devlink_linecard_type *types;
+	unsigned int types_count;
+	u32 rel_index;
+};
+
+unsigned int devlink_linecard_index(struct devlink_linecard *linecard)
+{
+	return linecard->index;
+}
+
+static struct devlink_linecard *
+devlink_linecard_get_by_index(struct devlink *devlink,
+			      unsigned int linecard_index)
+{
+	struct devlink_linecard *devlink_linecard;
+
+	list_for_each_entry(devlink_linecard, &devlink->linecard_list, list) {
+		if (devlink_linecard->index == linecard_index)
+			return devlink_linecard;
+	}
+	return NULL;
+}
+
+static bool devlink_linecard_index_exists(struct devlink *devlink,
+					  unsigned int linecard_index)
+{
+	return devlink_linecard_get_by_index(devlink, linecard_index);
+}
+
+static struct devlink_linecard *
+devlink_linecard_get_from_attrs(struct devlink *devlink, struct nlattr **attrs)
+{
+	if (attrs[DEVLINK_ATTR_LINECARD_INDEX]) {
+		u32 linecard_index = nla_get_u32(attrs[DEVLINK_ATTR_LINECARD_INDEX]);
+		struct devlink_linecard *linecard;
+
+		linecard = devlink_linecard_get_by_index(devlink, linecard_index);
+		if (!linecard)
+			return ERR_PTR(-ENODEV);
+		return linecard;
+	}
+	return ERR_PTR(-EINVAL);
+}
+
+static struct devlink_linecard *
+devlink_linecard_get_from_info(struct devlink *devlink, struct genl_info *info)
+{
+	return devlink_linecard_get_from_attrs(devlink, info->attrs);
+}
+
+struct devlink_linecard_type {
+	const char *type;
+	const void *priv;
+};
+
+static int devlink_nl_linecard_fill(struct sk_buff *msg,
+				    struct devlink *devlink,
+				    struct devlink_linecard *linecard,
+				    enum devlink_command cmd, u32 portid,
+				    u32 seq, int flags,
+				    struct netlink_ext_ack *extack)
+{
+	struct devlink_linecard_type *linecard_type;
+	struct nlattr *attr;
+	void *hdr;
+	int i;
+
+	hdr = genlmsg_put(msg, portid, seq, &devlink_nl_family, flags, cmd);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (devlink_nl_put_handle(msg, devlink))
+		goto nla_put_failure;
+	if (nla_put_u32(msg, DEVLINK_ATTR_LINECARD_INDEX, linecard->index))
+		goto nla_put_failure;
+	if (nla_put_u8(msg, DEVLINK_ATTR_LINECARD_STATE, linecard->state))
+		goto nla_put_failure;
+	if (linecard->type &&
+	    nla_put_string(msg, DEVLINK_ATTR_LINECARD_TYPE, linecard->type))
+		goto nla_put_failure;
+
+	if (linecard->types_count) {
+		attr = nla_nest_start(msg,
+				      DEVLINK_ATTR_LINECARD_SUPPORTED_TYPES);
+		if (!attr)
+			goto nla_put_failure;
+		for (i = 0; i < linecard->types_count; i++) {
+			linecard_type = &linecard->types[i];
+			if (nla_put_string(msg, DEVLINK_ATTR_LINECARD_TYPE,
+					   linecard_type->type)) {
+				nla_nest_cancel(msg, attr);
+				goto nla_put_failure;
+			}
+		}
+		nla_nest_end(msg, attr);
+	}
+
+	if (devlink_rel_devlink_handle_put(msg, devlink,
+					   linecard->rel_index,
+					   DEVLINK_ATTR_NESTED_DEVLINK,
+					   NULL))
+		goto nla_put_failure;
+
+	genlmsg_end(msg, hdr);
+	return 0;
+
+nla_put_failure:
+	genlmsg_cancel(msg, hdr);
+	return -EMSGSIZE;
+}
+
+static void devlink_linecard_notify(struct devlink_linecard *linecard,
+				    enum devlink_command cmd)
+{
+	struct devlink *devlink = linecard->devlink;
+	struct sk_buff *msg;
+	int err;
+
+	WARN_ON(cmd != DEVLINK_CMD_LINECARD_NEW &&
+		cmd != DEVLINK_CMD_LINECARD_DEL);
+
+	if (!__devl_is_registered(devlink) || !devlink_nl_notify_need(devlink))
+		return;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return;
+
+	err = devlink_nl_linecard_fill(msg, devlink, linecard, cmd, 0, 0, 0,
+				       NULL);
+	if (err) {
+		nlmsg_free(msg);
+		return;
+	}
+
+	devlink_nl_notify_send(devlink, msg);
+}
+
+void devlink_linecards_notify_register(struct devlink *devlink)
+{
+	struct devlink_linecard *linecard;
+
+	list_for_each_entry(linecard, &devlink->linecard_list, list)
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+}
+
+void devlink_linecards_notify_unregister(struct devlink *devlink)
+{
+	struct devlink_linecard *linecard;
+
+	list_for_each_entry_reverse(linecard, &devlink->linecard_list, list)
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_DEL);
+}
+
+int devlink_nl_linecard_get_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct devlink *devlink = devlink_nl_ctx(info)->devlink;
+	struct devlink_linecard *linecard;
+	struct sk_buff *msg;
+	int err;
+
+	linecard = devlink_linecard_get_from_info(devlink, info);
+	if (IS_ERR(linecard))
+		return PTR_ERR(linecard);
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	mutex_lock(&linecard->state_lock);
+	err = devlink_nl_linecard_fill(msg, devlink, linecard,
+				       DEVLINK_CMD_LINECARD_NEW,
+				       info->snd_portid, info->snd_seq, 0,
+				       info->extack);
+	mutex_unlock(&linecard->state_lock);
+	if (err) {
+		nlmsg_free(msg);
+		return err;
+	}
+
+	return genlmsg_reply(msg, info);
+}
+
+static int devlink_nl_linecard_get_dump_one(struct sk_buff *msg,
+					    struct devlink *devlink,
+					    struct netlink_callback *cb,
+					    int flags)
+{
+	struct devlink_nl_dump_state *state = devlink_dump_state(cb);
+	struct devlink_linecard *linecard;
+	int idx = 0;
+	int err = 0;
+
+	list_for_each_entry(linecard, &devlink->linecard_list, list) {
+		if (idx < state->idx) {
+			idx++;
+			continue;
+		}
+		mutex_lock(&linecard->state_lock);
+		err = devlink_nl_linecard_fill(msg, devlink, linecard,
+					       DEVLINK_CMD_LINECARD_NEW,
+					       NETLINK_CB(cb->skb).portid,
+					       cb->nlh->nlmsg_seq, flags,
+					       cb->extack);
+		mutex_unlock(&linecard->state_lock);
+		if (err) {
+			state->idx = idx;
+			break;
+		}
+		idx++;
+	}
+
+	return err;
+}
+
+int devlink_nl_linecard_get_dumpit(struct sk_buff *skb,
+				   struct netlink_callback *cb)
+{
+	return devlink_nl_dumpit(skb, cb, devlink_nl_linecard_get_dump_one);
+}
+
+static struct devlink_linecard_type *
+devlink_linecard_type_lookup(struct devlink_linecard *linecard,
+			     const char *type)
+{
+	struct devlink_linecard_type *linecard_type;
+	int i;
+
+	for (i = 0; i < linecard->types_count; i++) {
+		linecard_type = &linecard->types[i];
+		if (!strcmp(type, linecard_type->type))
+			return linecard_type;
+	}
+	return NULL;
+}
+
+static int devlink_linecard_type_set(struct devlink_linecard *linecard,
+				     const char *type,
+				     struct netlink_ext_ack *extack)
+{
+	const struct devlink_linecard_ops *ops = linecard->ops;
+	struct devlink_linecard_type *linecard_type;
+	int err;
+
+	mutex_lock(&linecard->state_lock);
+	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being provisioned");
+		err = -EBUSY;
+		goto out;
+	}
+	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being unprovisioned");
+		err = -EBUSY;
+		goto out;
+	}
+
+	linecard_type = devlink_linecard_type_lookup(linecard, type);
+	if (!linecard_type) {
+		NL_SET_ERR_MSG(extack, "Unsupported line card type provided");
+		err = -EINVAL;
+		goto out;
+	}
+
+	if (linecard->state != DEVLINK_LINECARD_STATE_UNPROVISIONED &&
+	    linecard->state != DEVLINK_LINECARD_STATE_PROVISIONING_FAILED) {
+		NL_SET_ERR_MSG(extack, "Line card already provisioned");
+		err = -EBUSY;
+		/* Check if the line card is provisioned in the same
+		 * way the user asks. In case it is, make the operation
+		 * to return success.
+		 */
+		if (ops->same_provision &&
+		    ops->same_provision(linecard, linecard->priv,
+					linecard_type->type,
+					linecard_type->priv))
+			err = 0;
+		goto out;
+	}
+
+	linecard->state = DEVLINK_LINECARD_STATE_PROVISIONING;
+	linecard->type = linecard_type->type;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+	err = ops->provision(linecard, linecard->priv, linecard_type->type,
+			     linecard_type->priv, extack);
+	if (err) {
+		/* Provisioning failed. Assume the linecard is unprovisioned
+		 * for future operations.
+		 */
+		mutex_lock(&linecard->state_lock);
+		linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+		linecard->type = NULL;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		mutex_unlock(&linecard->state_lock);
+	}
+	return err;
+
+out:
+	mutex_unlock(&linecard->state_lock);
+	return err;
+}
+
+static int devlink_linecard_type_unset(struct devlink_linecard *linecard,
+				       struct netlink_ext_ack *extack)
+{
+	int err;
+
+	mutex_lock(&linecard->state_lock);
+	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being provisioned");
+		err = -EBUSY;
+		goto out;
+	}
+	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being unprovisioned");
+		err = -EBUSY;
+		goto out;
+	}
+	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING_FAILED) {
+		linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+		linecard->type = NULL;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		err = 0;
+		goto out;
+	}
+
+	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONED) {
+		NL_SET_ERR_MSG(extack, "Line card is not provisioned");
+		err = 0;
+		goto out;
+	}
+	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONING;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+	err = linecard->ops->unprovision(linecard, linecard->priv,
+					 extack);
+	if (err) {
+		/* Unprovisioning failed. Assume the linecard is unprovisioned
+		 * for future operations.
+		 */
+		mutex_lock(&linecard->state_lock);
+		linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+		linecard->type = NULL;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		mutex_unlock(&linecard->state_lock);
+	}
+	return err;
+
+out:
+	mutex_unlock(&linecard->state_lock);
+	return err;
+}
+
+int devlink_nl_linecard_set_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct netlink_ext_ack *extack = info->extack;
+	struct devlink *devlink = devlink_nl_ctx(info)->devlink;
+	struct devlink_linecard *linecard;
+	int err;
+
+	linecard = devlink_linecard_get_from_info(devlink, info);
+	if (IS_ERR(linecard))
+		return PTR_ERR(linecard);
+
+	if (info->attrs[DEVLINK_ATTR_LINECARD_TYPE]) {
+		const char *type;
+
+		type = nla_data(info->attrs[DEVLINK_ATTR_LINECARD_TYPE]);
+		if (strcmp(type, "")) {
+			err = devlink_linecard_type_set(linecard, type, extack);
+			if (err)
+				return err;
+		} else {
+			err = devlink_linecard_type_unset(linecard, extack);
+			if (err)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
+static int devlink_linecard_types_init(struct devlink_linecard *linecard)
+{
+	struct devlink_linecard_type *linecard_type;
+	unsigned int count;
+	int i;
+
+	count = linecard->ops->types_count(linecard, linecard->priv);
+	linecard->types = kmalloc_objs(*linecard_type, count);
+	if (!linecard->types)
+		return -ENOMEM;
+	linecard->types_count = count;
+
+	for (i = 0; i < count; i++) {
+		linecard_type = &linecard->types[i];
+		linecard->ops->types_get(linecard, linecard->priv, i,
+					 &linecard_type->type,
+					 &linecard_type->priv);
+	}
+	return 0;
+}
+
+static void devlink_linecard_types_fini(struct devlink_linecard *linecard)
+{
+	kfree(linecard->types);
+}
+
+/**
+ *	devl_linecard_create - Create devlink linecard
+ *
+ *	@devlink: devlink
+ *	@linecard_index: driver-specific numerical identifier of the linecard
+ *	@ops: linecards ops
+ *	@priv: user priv pointer
+ *
+ *	Create devlink linecard instance with provided linecard index.
+ *	Caller can use any indexing, even hw-related one.
+ *
+ *	Return: Line card structure or an ERR_PTR() encoded error code.
+ */
+struct devlink_linecard *
+devl_linecard_create(struct devlink *devlink, unsigned int linecard_index,
+		     const struct devlink_linecard_ops *ops, void *priv)
+{
+	struct devlink_linecard *linecard;
+	int err;
+
+	if (WARN_ON(!ops || !ops->provision || !ops->unprovision ||
+		    !ops->types_count || !ops->types_get))
+		return ERR_PTR(-EINVAL);
+
+	if (devlink_linecard_index_exists(devlink, linecard_index))
+		return ERR_PTR(-EEXIST);
+
+	linecard = kzalloc_obj(*linecard);
+	if (!linecard)
+		return ERR_PTR(-ENOMEM);
+
+	linecard->devlink = devlink;
+	linecard->index = linecard_index;
+	linecard->ops = ops;
+	linecard->priv = priv;
+	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+	mutex_init(&linecard->state_lock);
+
+	err = devlink_linecard_types_init(linecard);
+	if (err) {
+		mutex_destroy(&linecard->state_lock);
+		kfree(linecard);
+		return ERR_PTR(err);
+	}
+
+	list_add_tail(&linecard->list, &devlink->linecard_list);
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	return linecard;
+}
+EXPORT_SYMBOL_GPL(devl_linecard_create);
+
+/**
+ *	devl_linecard_destroy - Destroy devlink linecard
+ *
+ *	@linecard: devlink linecard
+ */
+void devl_linecard_destroy(struct devlink_linecard *linecard)
+{
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_DEL);
+	list_del(&linecard->list);
+	devlink_linecard_types_fini(linecard);
+	mutex_destroy(&linecard->state_lock);
+	kfree(linecard);
+}
+EXPORT_SYMBOL_GPL(devl_linecard_destroy);
+
+/**
+ *	devlink_linecard_provision_set - Set provisioning on linecard
+ *
+ *	@linecard: devlink linecard
+ *	@type: linecard type
+ *
+ *	This is either called directly from the provision() op call or
+ *	as a result of the provision() op call asynchronously.
+ */
+void devlink_linecard_provision_set(struct devlink_linecard *linecard,
+				    const char *type)
+{
+	mutex_lock(&linecard->state_lock);
+	WARN_ON(linecard->type && strcmp(linecard->type, type));
+	linecard->state = DEVLINK_LINECARD_STATE_PROVISIONED;
+	linecard->type = type;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_provision_set);
+
+/**
+ *	devlink_linecard_provision_clear - Clear provisioning on linecard
+ *
+ *	@linecard: devlink linecard
+ *
+ *	This is either called directly from the unprovision() op call or
+ *	as a result of the unprovision() op call asynchronously.
+ */
+void devlink_linecard_provision_clear(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+	linecard->type = NULL;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_provision_clear);
+
+/**
+ *	devlink_linecard_provision_fail - Fail provisioning on linecard
+ *
+ *	@linecard: devlink linecard
+ *
+ *	This is either called directly from the provision() op call or
+ *	as a result of the provision() op call asynchronously.
+ */
+void devlink_linecard_provision_fail(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	linecard->state = DEVLINK_LINECARD_STATE_PROVISIONING_FAILED;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_provision_fail);
+
+/**
+ *	devlink_linecard_activate - Set linecard active
+ *
+ *	@linecard: devlink linecard
+ */
+void devlink_linecard_activate(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	WARN_ON(linecard->state != DEVLINK_LINECARD_STATE_PROVISIONED);
+	linecard->state = DEVLINK_LINECARD_STATE_ACTIVE;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_activate);
+
+/**
+ *	devlink_linecard_deactivate - Set linecard inactive
+ *
+ *	@linecard: devlink linecard
+ */
+void devlink_linecard_deactivate(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	switch (linecard->state) {
+	case DEVLINK_LINECARD_STATE_ACTIVE:
+		linecard->state = DEVLINK_LINECARD_STATE_PROVISIONED;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		break;
+	case DEVLINK_LINECARD_STATE_UNPROVISIONING:
+		/* Line card is being deactivated as part
+		 * of unprovisioning flow.
+		 */
+		break;
+	default:
+		WARN_ON(1);
+		break;
+	}
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_deactivate);
+
+static void devlink_linecard_rel_notify_cb(struct devlink *devlink,
+					   u32 linecard_index)
+{
+	struct devlink_linecard *linecard;
+
+	linecard = devlink_linecard_get_by_index(devlink, linecard_index);
+	if (!linecard)
+		return;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+}
+
+static void devlink_linecard_rel_cleanup_cb(struct devlink *devlink,
+					    u32 linecard_index, u32 rel_index)
+{
+	struct devlink_linecard *linecard;
+
+	linecard = devlink_linecard_get_by_index(devlink, linecard_index);
+	if (linecard && linecard->rel_index == rel_index)
+		linecard->rel_index = 0;
+}
+
+/**
+ *	devlink_linecard_nested_dl_set - Attach/detach nested devlink
+ *					 instance to linecard.
+ *
+ *	@linecard: devlink linecard
+ *	@nested_devlink: devlink instance to attach or NULL to detach
+ */
+int devlink_linecard_nested_dl_set(struct devlink_linecard *linecard,
+				   struct devlink *nested_devlink)
+{
+	return devlink_rel_nested_in_add(&linecard->rel_index,
+					 linecard->devlink->index,
+					 linecard->index,
+					 devlink_linecard_rel_notify_cb,
+					 devlink_linecard_rel_cleanup_cb,
+					 nested_devlink);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_nested_dl_set);