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, 297 insertions, 0 deletions

diff --git a/net/ethtool/features.c b/net/ethtool/features.c
new file mode 100644
index 000000000..d9455b30a
--- /dev/null
+++ b/net/ethtool/features.c
@@ -0,0 +1,297 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <net/netdev_lock.h>
+
+#include "bitset.h"
+#include "common.h"
+#include "netlink.h"
+
+struct features_req_info {
+	struct ethnl_req_info	base;
+};
+
+struct features_reply_data {
+	struct ethnl_reply_data	base;
+	u32			hw[ETHTOOL_DEV_FEATURE_WORDS];
+	u32			wanted[ETHTOOL_DEV_FEATURE_WORDS];
+	u32			active[ETHTOOL_DEV_FEATURE_WORDS];
+	u32			nochange[ETHTOOL_DEV_FEATURE_WORDS];
+	u32			all[ETHTOOL_DEV_FEATURE_WORDS];
+};
+
+#define FEATURES_REPDATA(__reply_base) \
+	container_of(__reply_base, struct features_reply_data, base)
+
+const struct nla_policy ethnl_features_get_policy[] = {
+	[ETHTOOL_A_FEATURES_HEADER]	=
+		NLA_POLICY_NESTED(ethnl_header_policy),
+};
+
+static void ethnl_features_to_bitmap32(u32 *dest, netdev_features_t src)
+{
+	unsigned int i;
+
+	for (i = 0; i < ETHTOOL_DEV_FEATURE_WORDS; i++)
+		dest[i] = src >> (32 * i);
+}
+
+static int features_prepare_data(const struct ethnl_req_info *req_base,
+				 struct ethnl_reply_data *reply_base,
+				 const struct genl_info *info)
+{
+	struct features_reply_data *data = FEATURES_REPDATA(reply_base);
+	struct net_device *dev = reply_base->dev;
+	netdev_features_t all_features;
+
+	ethnl_features_to_bitmap32(data->hw, dev->hw_features);
+	ethnl_features_to_bitmap32(data->wanted, dev->wanted_features);
+	ethnl_features_to_bitmap32(data->active, dev->features);
+	ethnl_features_to_bitmap32(data->nochange, NETIF_F_NEVER_CHANGE);
+	all_features = GENMASK_ULL(NETDEV_FEATURE_COUNT - 1, 0);
+	ethnl_features_to_bitmap32(data->all, all_features);
+
+	return 0;
+}
+
+static int features_reply_size(const struct ethnl_req_info *req_base,
+			       const struct ethnl_reply_data *reply_base)
+{
+	const struct features_reply_data *data = FEATURES_REPDATA(reply_base);
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	unsigned int len = 0;
+	int ret;
+
+	ret = ethnl_bitset32_size(data->hw, data->all, NETDEV_FEATURE_COUNT,
+				  netdev_features_strings, compact);
+	if (ret < 0)
+		return ret;
+	len += ret;
+	ret = ethnl_bitset32_size(data->wanted, NULL, NETDEV_FEATURE_COUNT,
+				  netdev_features_strings, compact);
+	if (ret < 0)
+		return ret;
+	len += ret;
+	ret = ethnl_bitset32_size(data->active, NULL, NETDEV_FEATURE_COUNT,
+				  netdev_features_strings, compact);
+	if (ret < 0)
+		return ret;
+	len += ret;
+	ret = ethnl_bitset32_size(data->nochange, NULL, NETDEV_FEATURE_COUNT,
+				  netdev_features_strings, compact);
+	if (ret < 0)
+		return ret;
+	len += ret;
+
+	return len;
+}
+
+static int features_fill_reply(struct sk_buff *skb,
+			       const struct ethnl_req_info *req_base,
+			       const struct ethnl_reply_data *reply_base)
+{
+	const struct features_reply_data *data = FEATURES_REPDATA(reply_base);
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	int ret;
+
+	ret = ethnl_put_bitset32(skb, ETHTOOL_A_FEATURES_HW, data->hw,
+				 data->all, NETDEV_FEATURE_COUNT,
+				 netdev_features_strings, compact);
+	if (ret < 0)
+		return ret;
+	ret = ethnl_put_bitset32(skb, ETHTOOL_A_FEATURES_WANTED, data->wanted,
+				 NULL, NETDEV_FEATURE_COUNT,
+				 netdev_features_strings, compact);
+	if (ret < 0)
+		return ret;
+	ret = ethnl_put_bitset32(skb, ETHTOOL_A_FEATURES_ACTIVE, data->active,
+				 NULL, NETDEV_FEATURE_COUNT,
+				 netdev_features_strings, compact);
+	if (ret < 0)
+		return ret;
+	return ethnl_put_bitset32(skb, ETHTOOL_A_FEATURES_NOCHANGE,
+				  data->nochange, NULL, NETDEV_FEATURE_COUNT,
+				  netdev_features_strings, compact);
+}
+
+const struct ethnl_request_ops ethnl_features_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_FEATURES_GET,
+	.reply_cmd		= ETHTOOL_MSG_FEATURES_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_FEATURES_HEADER,
+	.req_info_size		= sizeof(struct features_req_info),
+	.reply_data_size	= sizeof(struct features_reply_data),
+
+	.prepare_data		= features_prepare_data,
+	.reply_size		= features_reply_size,
+	.fill_reply		= features_fill_reply,
+};
+
+/* FEATURES_SET */
+
+const struct nla_policy ethnl_features_set_policy[] = {
+	[ETHTOOL_A_FEATURES_HEADER]	=
+		NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_FEATURES_WANTED]	= { .type = NLA_NESTED },
+};
+
+static void ethnl_features_to_bitmap(unsigned long *dest, netdev_features_t val)
+{
+	const unsigned int words = BITS_TO_LONGS(NETDEV_FEATURE_COUNT);
+	unsigned int i;
+
+	for (i = 0; i < words; i++)
+		dest[i] = (unsigned long)(val >> (i * BITS_PER_LONG));
+}
+
+static netdev_features_t ethnl_bitmap_to_features(unsigned long *src)
+{
+	const unsigned int nft_bits = sizeof(netdev_features_t) * BITS_PER_BYTE;
+	const unsigned int words = BITS_TO_LONGS(NETDEV_FEATURE_COUNT);
+	netdev_features_t ret = 0;
+	unsigned int i;
+
+	for (i = 0; i < words; i++)
+		ret |= (netdev_features_t)(src[i]) << (i * BITS_PER_LONG);
+	ret &= ~(netdev_features_t)0 >> (nft_bits - NETDEV_FEATURE_COUNT);
+	return ret;
+}
+
+static int features_send_reply(struct net_device *dev, struct genl_info *info,
+			       const unsigned long *wanted,
+			       const unsigned long *wanted_mask,
+			       const unsigned long *active,
+			       const unsigned long *active_mask, bool compact)
+{
+	struct sk_buff *rskb;
+	void *reply_payload;
+	int reply_len = 0;
+	int ret;
+
+	reply_len = ethnl_reply_header_size();
+	ret = ethnl_bitset_size(wanted, wanted_mask, NETDEV_FEATURE_COUNT,
+				netdev_features_strings, compact);
+	if (ret < 0)
+		goto err;
+	reply_len += ret;
+	ret = ethnl_bitset_size(active, active_mask, NETDEV_FEATURE_COUNT,
+				netdev_features_strings, compact);
+	if (ret < 0)
+		goto err;
+	reply_len += ret;
+
+	ret = -ENOMEM;
+	rskb = ethnl_reply_init(reply_len, dev, ETHTOOL_MSG_FEATURES_SET_REPLY,
+				ETHTOOL_A_FEATURES_HEADER, info,
+				&reply_payload);
+	if (!rskb)
+		goto err;
+
+	ret = ethnl_put_bitset(rskb, ETHTOOL_A_FEATURES_WANTED, wanted,
+			       wanted_mask, NETDEV_FEATURE_COUNT,
+			       netdev_features_strings, compact);
+	if (ret < 0)
+		goto nla_put_failure;
+	ret = ethnl_put_bitset(rskb, ETHTOOL_A_FEATURES_ACTIVE, active,
+			       active_mask, NETDEV_FEATURE_COUNT,
+			       netdev_features_strings, compact);
+	if (ret < 0)
+		goto nla_put_failure;
+
+	genlmsg_end(rskb, reply_payload);
+	ret = genlmsg_reply(rskb, info);
+	return ret;
+
+nla_put_failure:
+	nlmsg_free(rskb);
+	WARN_ONCE(1, "calculated message payload length (%d) not sufficient\n",
+		  reply_len);
+err:
+	GENL_SET_ERR_MSG(info, "failed to send reply message");
+	return ret;
+}
+
+int ethnl_set_features(struct sk_buff *skb, struct genl_info *info)
+{
+	DECLARE_BITMAP(wanted_diff_mask, NETDEV_FEATURE_COUNT);
+	DECLARE_BITMAP(active_diff_mask, NETDEV_FEATURE_COUNT);
+	DECLARE_BITMAP(old_active, NETDEV_FEATURE_COUNT);
+	DECLARE_BITMAP(old_wanted, NETDEV_FEATURE_COUNT);
+	DECLARE_BITMAP(new_active, NETDEV_FEATURE_COUNT);
+	DECLARE_BITMAP(new_wanted, NETDEV_FEATURE_COUNT);
+	DECLARE_BITMAP(req_wanted, NETDEV_FEATURE_COUNT);
+	DECLARE_BITMAP(req_mask, NETDEV_FEATURE_COUNT);
+	struct ethnl_req_info req_info = {};
+	struct nlattr **tb = info->attrs;
+	struct net_device *dev;
+	bool mod;
+	int ret;
+
+	if (!tb[ETHTOOL_A_FEATURES_WANTED])
+		return -EINVAL;
+	ret = ethnl_parse_header_dev_get(&req_info,
+					 tb[ETHTOOL_A_FEATURES_HEADER],
+					 genl_info_net(info), info->extack,
+					 true);
+	if (ret < 0)
+		return ret;
+	dev = req_info.dev;
+
+	rtnl_lock();
+	netdev_lock_ops(dev);
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto out_unlock;
+	ethnl_features_to_bitmap(old_active, dev->features);
+	ethnl_features_to_bitmap(old_wanted, dev->wanted_features);
+	ret = ethnl_parse_bitset(req_wanted, req_mask, NETDEV_FEATURE_COUNT,
+				 tb[ETHTOOL_A_FEATURES_WANTED],
+				 netdev_features_strings, info->extack);
+	if (ret < 0)
+		goto out_ops;
+	if (ethnl_bitmap_to_features(req_mask) & ~NETIF_F_ETHTOOL_BITS) {
+		GENL_SET_ERR_MSG(info, "attempt to change non-ethtool features");
+		ret = -EINVAL;
+		goto out_ops;
+	}
+
+	/* set req_wanted bits not in req_mask from old_wanted */
+	bitmap_and(req_wanted, req_wanted, req_mask, NETDEV_FEATURE_COUNT);
+	bitmap_andnot(new_wanted, old_wanted, req_mask, NETDEV_FEATURE_COUNT);
+	bitmap_or(req_wanted, new_wanted, req_wanted, NETDEV_FEATURE_COUNT);
+	if (!bitmap_equal(req_wanted, old_wanted, NETDEV_FEATURE_COUNT)) {
+		dev->wanted_features &= ~dev->hw_features;
+		dev->wanted_features |= ethnl_bitmap_to_features(req_wanted) & dev->hw_features;
+		__netdev_update_features(dev);
+	}
+	ethnl_features_to_bitmap(new_active, dev->features);
+	mod = !bitmap_equal(old_active, new_active, NETDEV_FEATURE_COUNT);
+
+	ret = 0;
+	if (!(req_info.flags & ETHTOOL_FLAG_OMIT_REPLY)) {
+		bool compact = req_info.flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+
+		bitmap_xor(wanted_diff_mask, req_wanted, new_active,
+			   NETDEV_FEATURE_COUNT);
+		bitmap_xor(active_diff_mask, old_active, new_active,
+			   NETDEV_FEATURE_COUNT);
+		bitmap_and(wanted_diff_mask, wanted_diff_mask, req_mask,
+			   NETDEV_FEATURE_COUNT);
+		bitmap_and(req_wanted, req_wanted, wanted_diff_mask,
+			   NETDEV_FEATURE_COUNT);
+		bitmap_and(new_active, new_active, active_diff_mask,
+			   NETDEV_FEATURE_COUNT);
+
+		ret = features_send_reply(dev, info, req_wanted,
+					  wanted_diff_mask, new_active,
+					  active_diff_mask, compact);
+	}
+	if (mod)
+		netdev_features_change(dev);
+
+out_ops:
+	ethnl_ops_complete(dev);
+out_unlock:
+	netdev_unlock_ops(dev);
+	rtnl_unlock();
+	ethnl_parse_header_dev_put(&req_info);
+	return ret;
+}