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, 464 insertions, 0 deletions

diff --git a/net/ethtool/tsconfig.c b/net/ethtool/tsconfig.c
new file mode 100644
index 000000000..6be3aa5d4
--- /dev/null
+++ b/net/ethtool/tsconfig.c
@@ -0,0 +1,464 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/net_tstamp.h>
+#include <linux/ptp_clock_kernel.h>
+#include <net/netdev_lock.h>
+
+#include "bitset.h"
+#include "common.h"
+#include "netlink.h"
+#include "ts.h"
+#include "../core/dev.h"
+
+struct tsconfig_req_info {
+	struct ethnl_req_info base;
+};
+
+struct tsconfig_reply_data {
+	struct ethnl_reply_data		base;
+	struct hwtstamp_provider_desc	hwprov_desc;
+	struct {
+		u32 tx_type;
+		u32 rx_filter;
+		u32 flags;
+	} hwtst_config;
+};
+
+#define TSCONFIG_REPDATA(__reply_base) \
+	container_of(__reply_base, struct tsconfig_reply_data, base)
+
+const struct nla_policy ethnl_tsconfig_get_policy[ETHTOOL_A_TSCONFIG_HEADER + 1] = {
+	[ETHTOOL_A_TSCONFIG_HEADER]		=
+		NLA_POLICY_NESTED(ethnl_header_policy),
+};
+
+static int tsconfig_prepare_data(const struct ethnl_req_info *req_base,
+				 struct ethnl_reply_data *reply_base,
+				 const struct genl_info *info)
+{
+	struct tsconfig_reply_data *data = TSCONFIG_REPDATA(reply_base);
+	struct hwtstamp_provider *hwprov = NULL;
+	struct net_device *dev = reply_base->dev;
+	struct kernel_hwtstamp_config cfg = {};
+	int ret;
+
+	if (!dev->netdev_ops->ndo_hwtstamp_get)
+		return -EOPNOTSUPP;
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		return ret;
+
+	ret = dev_get_hwtstamp_phylib(dev, &cfg);
+	if (ret)
+		goto out;
+
+	data->hwtst_config.tx_type = BIT(cfg.tx_type);
+	data->hwtst_config.rx_filter = BIT(cfg.rx_filter);
+	data->hwtst_config.flags = cfg.flags;
+
+	data->hwprov_desc.index = -1;
+	hwprov = netdev_ops_lock_dereference(dev->hwprov, dev);
+	if (hwprov) {
+		data->hwprov_desc.index = hwprov->desc.index;
+		data->hwprov_desc.qualifier = hwprov->desc.qualifier;
+	} else {
+		struct kernel_ethtool_ts_info ts_info = {};
+
+		ts_info.phc_index = -1;
+		ret = __ethtool_get_ts_info(dev, &ts_info);
+		if (ret)
+			goto out;
+
+		if (ts_info.phc_index == -1) {
+			ret = -ENODEV;
+			goto out;
+		}
+
+		data->hwprov_desc.index = ts_info.phc_index;
+		data->hwprov_desc.qualifier = ts_info.phc_qualifier;
+	}
+
+out:
+	ethnl_ops_complete(dev);
+	return ret;
+}
+
+static int tsconfig_reply_size(const struct ethnl_req_info *req_base,
+			       const struct ethnl_reply_data *reply_base)
+{
+	const struct tsconfig_reply_data *data = TSCONFIG_REPDATA(reply_base);
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	int len = 0;
+	int ret;
+
+	BUILD_BUG_ON(__HWTSTAMP_TX_CNT > 32);
+	BUILD_BUG_ON(__HWTSTAMP_FILTER_CNT > 32);
+	BUILD_BUG_ON(__HWTSTAMP_FLAG_CNT > 32);
+
+	if (data->hwtst_config.flags) {
+		ret = ethnl_bitset32_size(&data->hwtst_config.flags,
+					  NULL, __HWTSTAMP_FLAG_CNT,
+					  ts_flags_names, compact);
+		if (ret < 0)
+			return ret;
+		len += ret;	/* _TSCONFIG_HWTSTAMP_FLAGS */
+	}
+
+	if (data->hwtst_config.tx_type) {
+		ret = ethnl_bitset32_size(&data->hwtst_config.tx_type,
+					  NULL, __HWTSTAMP_TX_CNT,
+					  ts_tx_type_names, compact);
+		if (ret < 0)
+			return ret;
+		len += ret;	/* _TSCONFIG_TX_TYPES */
+	}
+	if (data->hwtst_config.rx_filter) {
+		ret = ethnl_bitset32_size(&data->hwtst_config.rx_filter,
+					  NULL, __HWTSTAMP_FILTER_CNT,
+					  ts_rx_filter_names, compact);
+		if (ret < 0)
+			return ret;
+		len += ret;	/* _TSCONFIG_RX_FILTERS */
+	}
+
+	if (data->hwprov_desc.index >= 0)
+		/* _TSCONFIG_HWTSTAMP_PROVIDER */
+		len += nla_total_size(0) +
+		       2 * nla_total_size(sizeof(u32));
+
+	return len;
+}
+
+static int tsconfig_fill_reply(struct sk_buff *skb,
+			       const struct ethnl_req_info *req_base,
+			       const struct ethnl_reply_data *reply_base)
+{
+	const struct tsconfig_reply_data *data = TSCONFIG_REPDATA(reply_base);
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	int ret;
+
+	if (data->hwtst_config.flags) {
+		ret = ethnl_put_bitset32(skb, ETHTOOL_A_TSCONFIG_HWTSTAMP_FLAGS,
+					 &data->hwtst_config.flags, NULL,
+					 __HWTSTAMP_FLAG_CNT,
+					 ts_flags_names, compact);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (data->hwtst_config.tx_type) {
+		ret = ethnl_put_bitset32(skb, ETHTOOL_A_TSCONFIG_TX_TYPES,
+					 &data->hwtst_config.tx_type, NULL,
+					 __HWTSTAMP_TX_CNT,
+					 ts_tx_type_names, compact);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (data->hwtst_config.rx_filter) {
+		ret = ethnl_put_bitset32(skb, ETHTOOL_A_TSCONFIG_RX_FILTERS,
+					 &data->hwtst_config.rx_filter,
+					 NULL, __HWTSTAMP_FILTER_CNT,
+					 ts_rx_filter_names, compact);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (data->hwprov_desc.index >= 0) {
+		struct nlattr *nest;
+
+		nest = nla_nest_start(skb, ETHTOOL_A_TSCONFIG_HWTSTAMP_PROVIDER);
+		if (!nest)
+			return -EMSGSIZE;
+
+		if (nla_put_u32(skb, ETHTOOL_A_TS_HWTSTAMP_PROVIDER_INDEX,
+				data->hwprov_desc.index) ||
+		    nla_put_u32(skb,
+				ETHTOOL_A_TS_HWTSTAMP_PROVIDER_QUALIFIER,
+				data->hwprov_desc.qualifier)) {
+			nla_nest_cancel(skb, nest);
+			return -EMSGSIZE;
+		}
+
+		nla_nest_end(skb, nest);
+	}
+	return 0;
+}
+
+/* TSCONFIG_SET */
+const struct nla_policy ethnl_tsconfig_set_policy[ETHTOOL_A_TSCONFIG_MAX + 1] = {
+	[ETHTOOL_A_TSCONFIG_HEADER] = NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_TSCONFIG_HWTSTAMP_PROVIDER] =
+		NLA_POLICY_NESTED(ethnl_ts_hwtst_prov_policy),
+	[ETHTOOL_A_TSCONFIG_HWTSTAMP_FLAGS] = { .type = NLA_NESTED },
+	[ETHTOOL_A_TSCONFIG_RX_FILTERS] = { .type = NLA_NESTED },
+	[ETHTOOL_A_TSCONFIG_TX_TYPES] = { .type = NLA_NESTED },
+};
+
+static int tsconfig_send_reply(struct net_device *dev, struct genl_info *info)
+{
+	struct tsconfig_reply_data *reply_data;
+	struct tsconfig_req_info *req_info;
+	struct sk_buff *rskb;
+	void *reply_payload;
+	int reply_len = 0;
+	int ret;
+
+	req_info = kzalloc_obj(*req_info);
+	if (!req_info)
+		return -ENOMEM;
+	reply_data = kmalloc_obj(*reply_data);
+	if (!reply_data) {
+		kfree(req_info);
+		return -ENOMEM;
+	}
+
+	netdev_assert_locked_ops_compat(dev);
+	reply_data->base.dev = dev;
+	ret = tsconfig_prepare_data(&req_info->base, &reply_data->base, info);
+	if (ret < 0)
+		goto err_cleanup;
+
+	ret = tsconfig_reply_size(&req_info->base, &reply_data->base);
+	if (ret < 0)
+		goto err_cleanup;
+
+	reply_len = ret + ethnl_reply_header_size();
+	rskb = ethnl_reply_init(reply_len, dev, ETHTOOL_MSG_TSCONFIG_SET_REPLY,
+				ETHTOOL_A_TSCONFIG_HEADER, info, &reply_payload);
+	if (!rskb) {
+		ret = -ENOMEM;
+		goto err_cleanup;
+	}
+
+	ret = tsconfig_fill_reply(rskb, &req_info->base, &reply_data->base);
+	if (ret < 0)
+		goto err_free_msg;
+
+	genlmsg_end(rskb, reply_payload);
+	ret = genlmsg_reply(rskb, info);
+	rskb = NULL;
+
+err_free_msg:
+	nlmsg_free(rskb);
+err_cleanup:
+	kfree(reply_data);
+	kfree(req_info);
+	return ret;
+}
+
+static int ethnl_set_tsconfig_validate(struct ethnl_req_info *req_base,
+				       struct genl_info *info)
+{
+	const struct net_device_ops *ops = req_base->dev->netdev_ops;
+
+	if (!ops->ndo_hwtstamp_set || !ops->ndo_hwtstamp_get)
+		return -EOPNOTSUPP;
+
+	return 1;
+}
+
+static struct hwtstamp_provider *
+tsconfig_set_hwprov_from_desc(struct net_device *dev,
+			      struct genl_info *info,
+			      struct hwtstamp_provider_desc *hwprov_desc)
+{
+	struct kernel_ethtool_ts_info ts_info;
+	struct hwtstamp_provider *hwprov;
+	struct nlattr **tb = info->attrs;
+	struct phy_device *phy = NULL;
+	enum hwtstamp_source source;
+	int ret;
+
+	ret = ethtool_net_get_ts_info_by_phc(dev, &ts_info, hwprov_desc);
+	if (!ret) {
+		/* Found */
+		source = HWTSTAMP_SOURCE_NETDEV;
+	} else {
+		phy = ethtool_phy_get_ts_info_by_phc(dev, &ts_info, hwprov_desc);
+		if (IS_ERR(phy)) {
+			if (PTR_ERR(phy) == -ENODEV)
+				NL_SET_ERR_MSG_ATTR(info->extack,
+						    tb[ETHTOOL_A_TSCONFIG_HWTSTAMP_PROVIDER],
+						    "phc not in this net device topology");
+			return ERR_CAST(phy);
+		}
+
+		source = HWTSTAMP_SOURCE_PHYLIB;
+	}
+
+	hwprov = kzalloc_obj(*hwprov);
+	if (!hwprov)
+		return ERR_PTR(-ENOMEM);
+
+	hwprov->desc.index = hwprov_desc->index;
+	hwprov->desc.qualifier = hwprov_desc->qualifier;
+	hwprov->source = source;
+	hwprov->phydev = phy;
+
+	return hwprov;
+}
+
+static int ethnl_set_tsconfig(struct ethnl_req_info *req_base,
+			      struct genl_info *info)
+{
+	struct kernel_hwtstamp_config hwtst_config = {0};
+	bool hwprov_mod = false, config_mod = false;
+	struct hwtstamp_provider *hwprov = NULL;
+	struct net_device *dev = req_base->dev;
+	struct nlattr **tb = info->attrs;
+	int ret;
+
+	if (!netif_device_present(dev))
+		return -ENODEV;
+
+	if (tb[ETHTOOL_A_TSCONFIG_HWTSTAMP_PROVIDER]) {
+		struct hwtstamp_provider_desc __hwprov_desc = {.index = -1};
+		struct hwtstamp_provider *__hwprov;
+
+		__hwprov = netdev_ops_lock_dereference(dev->hwprov, dev);
+		if (__hwprov) {
+			__hwprov_desc.index = __hwprov->desc.index;
+			__hwprov_desc.qualifier = __hwprov->desc.qualifier;
+		}
+
+		ret = ts_parse_hwtst_provider(tb[ETHTOOL_A_TSCONFIG_HWTSTAMP_PROVIDER],
+					      &__hwprov_desc, info->extack,
+					      &hwprov_mod);
+		if (ret < 0)
+			return ret;
+
+		if (hwprov_mod) {
+			hwprov = tsconfig_set_hwprov_from_desc(dev, info,
+							       &__hwprov_desc);
+			if (IS_ERR(hwprov))
+				return PTR_ERR(hwprov);
+		}
+	}
+
+	/* Get current hwtstamp config if we are not changing the
+	 * hwtstamp source. It will be zeroed in the other case.
+	 */
+	if (!hwprov_mod) {
+		ret = dev_get_hwtstamp_phylib(dev, &hwtst_config);
+		if (ret < 0 && ret != -EOPNOTSUPP)
+			goto err_free_hwprov;
+	}
+
+	/* Get the hwtstamp config from netlink */
+	if (tb[ETHTOOL_A_TSCONFIG_TX_TYPES]) {
+		u32 req_tx_type;
+
+		req_tx_type = BIT(hwtst_config.tx_type);
+		ret = ethnl_update_bitset32(&req_tx_type,
+					    __HWTSTAMP_TX_CNT,
+					    tb[ETHTOOL_A_TSCONFIG_TX_TYPES],
+					    ts_tx_type_names, info->extack,
+					    &config_mod);
+		if (ret < 0)
+			goto err_free_hwprov;
+
+		/* Select exactly one tx type at a time */
+		if (hweight32(req_tx_type) != 1) {
+			NL_SET_BAD_ATTR(info->extack,
+					tb[ETHTOOL_A_TSCONFIG_TX_TYPES]);
+			ret = -EINVAL;
+			goto err_free_hwprov;
+		}
+
+		hwtst_config.tx_type = ffs(req_tx_type) - 1;
+	}
+
+	if (tb[ETHTOOL_A_TSCONFIG_RX_FILTERS]) {
+		u32 req_rx_filter;
+
+		req_rx_filter = BIT(hwtst_config.rx_filter);
+		ret = ethnl_update_bitset32(&req_rx_filter,
+					    __HWTSTAMP_FILTER_CNT,
+					    tb[ETHTOOL_A_TSCONFIG_RX_FILTERS],
+					    ts_rx_filter_names, info->extack,
+					    &config_mod);
+		if (ret < 0)
+			goto err_free_hwprov;
+
+		/* Select exactly one rx filter at a time */
+		if (hweight32(req_rx_filter) != 1) {
+			NL_SET_BAD_ATTR(info->extack,
+					tb[ETHTOOL_A_TSCONFIG_RX_FILTERS]);
+			ret = -EINVAL;
+			goto err_free_hwprov;
+		}
+
+		hwtst_config.rx_filter = ffs(req_rx_filter) - 1;
+	}
+
+	if (tb[ETHTOOL_A_TSCONFIG_HWTSTAMP_FLAGS]) {
+		ret = ethnl_update_bitset32(&hwtst_config.flags,
+					    __HWTSTAMP_FLAG_CNT,
+					    tb[ETHTOOL_A_TSCONFIG_HWTSTAMP_FLAGS],
+					    ts_flags_names, info->extack,
+					    &config_mod);
+		if (ret < 0)
+			goto err_free_hwprov;
+	}
+
+	ret = net_hwtstamp_validate(&hwtst_config);
+	if (ret)
+		goto err_free_hwprov;
+
+	if (hwprov_mod) {
+		struct kernel_hwtstamp_config zero_config = {0};
+		struct hwtstamp_provider *__hwprov;
+
+		/* Disable current time stamping if we try to enable
+		 * another one
+		 */
+		ret = dev_set_hwtstamp_phylib(dev, &zero_config, info->extack);
+		if (ret < 0)
+			goto err_free_hwprov;
+
+		/* Change the selected hwtstamp source */
+		__hwprov = rcu_replace_pointer(dev->hwprov, hwprov,
+					       netdev_is_locked_ops_compat(dev));
+		if (__hwprov)
+			kfree_rcu(__hwprov, rcu_head);
+	}
+
+	if (config_mod) {
+		ret = dev_set_hwtstamp_phylib(dev, &hwtst_config,
+					      info->extack);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = tsconfig_send_reply(dev, info);
+	if (ret && ret != -EOPNOTSUPP) {
+		NL_SET_ERR_MSG(info->extack,
+			       "error while reading the new configuration set");
+		return ret;
+	}
+
+	/* tsconfig has no notification */
+	return 0;
+
+err_free_hwprov:
+	kfree(hwprov);
+
+	return ret;
+}
+
+const struct ethnl_request_ops ethnl_tsconfig_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_TSCONFIG_GET,
+	.reply_cmd		= ETHTOOL_MSG_TSCONFIG_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_TSCONFIG_HEADER,
+	.req_info_size		= sizeof(struct tsconfig_req_info),
+	.reply_data_size	= sizeof(struct tsconfig_reply_data),
+
+	.prepare_data		= tsconfig_prepare_data,
+	.reply_size		= tsconfig_reply_size,
+	.fill_reply		= tsconfig_fill_reply,
+
+	.set_validate		= ethnl_set_tsconfig_validate,
+	.set			= ethnl_set_tsconfig,
+};