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, 364 insertions, 0 deletions

diff --git a/net/ethtool/fec.c b/net/ethtool/fec.c
new file mode 100644
index 000000000..e2d539271
--- /dev/null
+++ b/net/ethtool/fec.c
@@ -0,0 +1,364 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "bitset.h"
+#include "common.h"
+#include "netlink.h"
+
+struct fec_req_info {
+	struct ethnl_req_info		base;
+};
+
+struct fec_reply_data {
+	struct ethnl_reply_data		base;
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(fec_link_modes);
+	u32 active_fec;
+	u8 fec_auto;
+	struct fec_stat_grp {
+		u64 stats[1 + ETHTOOL_MAX_LANES];
+		u8 cnt;
+	} corr, uncorr, corr_bits;
+	struct ethtool_fec_hist fec_stat_hist;
+};
+
+#define FEC_REPDATA(__reply_base) \
+	container_of(__reply_base, struct fec_reply_data, base)
+
+#define ETHTOOL_FEC_MASK	((ETHTOOL_FEC_LLRS << 1) - 1)
+
+const struct nla_policy ethnl_fec_get_policy[ETHTOOL_A_FEC_HEADER + 1] = {
+	[ETHTOOL_A_FEC_HEADER]	= NLA_POLICY_NESTED(ethnl_header_policy_stats),
+};
+
+static void
+ethtool_fec_to_link_modes(u32 fec, unsigned long *link_modes, u8 *fec_auto)
+{
+	if (fec_auto)
+		*fec_auto = !!(fec & ETHTOOL_FEC_AUTO);
+
+	if (fec & ETHTOOL_FEC_OFF)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_NONE_BIT, link_modes);
+	if (fec & ETHTOOL_FEC_RS)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_RS_BIT, link_modes);
+	if (fec & ETHTOOL_FEC_BASER)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_BASER_BIT, link_modes);
+	if (fec & ETHTOOL_FEC_LLRS)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_LLRS_BIT, link_modes);
+}
+
+static int
+ethtool_link_modes_to_fecparam(struct ethtool_fecparam *fec,
+			       unsigned long *link_modes, u8 fec_auto)
+{
+	memset(fec, 0, sizeof(*fec));
+
+	if (fec_auto)
+		fec->fec |= ETHTOOL_FEC_AUTO;
+
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_NONE_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_OFF;
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_RS_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_RS;
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_BASER_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_BASER;
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_LLRS_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_LLRS;
+
+	if (!bitmap_empty(link_modes, __ETHTOOL_LINK_MODE_MASK_NBITS))
+		return -EINVAL;
+
+	return 0;
+}
+
+static void
+fec_stats_recalc(struct fec_stat_grp *grp, struct ethtool_fec_stat *stats)
+{
+	int i;
+
+	if (stats->lanes[0] == ETHTOOL_STAT_NOT_SET) {
+		grp->stats[0] = stats->total;
+		grp->cnt = stats->total != ETHTOOL_STAT_NOT_SET;
+		return;
+	}
+
+	grp->cnt = 1;
+	grp->stats[0] = 0;
+	for (i = 0; i < ETHTOOL_MAX_LANES; i++) {
+		if (stats->lanes[i] == ETHTOOL_STAT_NOT_SET)
+			break;
+
+		grp->stats[0] += stats->lanes[i];
+		grp->stats[grp->cnt++] = stats->lanes[i];
+	}
+}
+
+static int fec_prepare_data(const struct ethnl_req_info *req_base,
+			    struct ethnl_reply_data *reply_base,
+			    const struct genl_info *info)
+{
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(active_fec_modes) = {};
+	struct fec_reply_data *data = FEC_REPDATA(reply_base);
+	struct net_device *dev = reply_base->dev;
+	struct ethtool_fecparam fec = {};
+	int ret;
+
+	if (!dev->ethtool_ops->get_fecparam)
+		return -EOPNOTSUPP;
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		return ret;
+	ret = dev->ethtool_ops->get_fecparam(dev, &fec);
+	if (ret)
+		goto out_complete;
+	if (req_base->flags & ETHTOOL_FLAG_STATS &&
+	    dev->ethtool_ops->get_fec_stats) {
+		struct ethtool_fec_stats stats;
+
+		ethtool_stats_init((u64 *)&stats, sizeof(stats) / 8);
+		ethtool_stats_init((u64 *)data->fec_stat_hist.values,
+				   sizeof(data->fec_stat_hist.values) / 8);
+		dev->ethtool_ops->get_fec_stats(dev, &stats,
+						&data->fec_stat_hist);
+
+		fec_stats_recalc(&data->corr, &stats.corrected_blocks);
+		fec_stats_recalc(&data->uncorr, &stats.uncorrectable_blocks);
+		fec_stats_recalc(&data->corr_bits, &stats.corrected_bits);
+	}
+
+	WARN_ON_ONCE(fec.reserved);
+
+	ethtool_fec_to_link_modes(fec.fec, data->fec_link_modes,
+				  &data->fec_auto);
+
+	ethtool_fec_to_link_modes(fec.active_fec, active_fec_modes, NULL);
+	data->active_fec = find_first_bit(active_fec_modes,
+					  __ETHTOOL_LINK_MODE_MASK_NBITS);
+	/* Don't report attr if no FEC mode set. Note that
+	 * ethtool_fecparam_to_link_modes() ignores NONE and AUTO.
+	 */
+	if (data->active_fec == __ETHTOOL_LINK_MODE_MASK_NBITS)
+		data->active_fec = 0;
+
+out_complete:
+	ethnl_ops_complete(dev);
+	return ret;
+}
+
+static int fec_reply_size(const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	const struct fec_reply_data *data = FEC_REPDATA(reply_base);
+	int len = 0;
+	int ret;
+
+	ret = ethnl_bitset_size(data->fec_link_modes, NULL,
+				__ETHTOOL_LINK_MODE_MASK_NBITS,
+				link_mode_names, compact);
+	if (ret < 0)
+		return ret;
+	len += ret;
+
+	len += nla_total_size(sizeof(u8)) +	/* _FEC_AUTO */
+	       nla_total_size(sizeof(u32));	/* _FEC_ACTIVE */
+
+	if (req_base->flags & ETHTOOL_FLAG_STATS) {
+		len += 3 * nla_total_size_64bit(sizeof(u64) *
+						(1 + ETHTOOL_MAX_LANES));
+		/* add FEC bins information */
+		len += (nla_total_size(0) +  /* _A_FEC_HIST */
+			nla_total_size(4) +  /* _A_FEC_HIST_BIN_LOW */
+			nla_total_size(4) +  /* _A_FEC_HIST_BIN_HI */
+			/* _A_FEC_HIST_BIN_VAL + per-lane values */
+			nla_total_size_64bit(sizeof(u64)) +
+			nla_total_size_64bit(sizeof(u64) * ETHTOOL_MAX_LANES)) *
+			ETHTOOL_FEC_HIST_MAX;
+	}
+
+	return len;
+}
+
+static int fec_put_hist(struct sk_buff *skb,
+			const struct ethtool_fec_hist *hist)
+{
+	const struct ethtool_fec_hist_range *ranges = hist->ranges;
+	const struct ethtool_fec_hist_value *values = hist->values;
+	struct nlattr *nest;
+	int i, j;
+	u64 sum;
+
+	if (!ranges)
+		return 0;
+
+	for (i = 0; i < ETHTOOL_FEC_HIST_MAX; i++) {
+		if (i && !ranges[i].low && !ranges[i].high)
+			break;
+
+		if (WARN_ON_ONCE(values[i].sum == ETHTOOL_STAT_NOT_SET &&
+				 values[i].per_lane[0] == ETHTOOL_STAT_NOT_SET))
+			break;
+
+		nest = nla_nest_start(skb, ETHTOOL_A_FEC_STAT_HIST);
+		if (!nest)
+			return -EMSGSIZE;
+
+		if (nla_put_u32(skb, ETHTOOL_A_FEC_HIST_BIN_LOW,
+				ranges[i].low) ||
+		    nla_put_u32(skb, ETHTOOL_A_FEC_HIST_BIN_HIGH,
+				ranges[i].high))
+			goto err_cancel_hist;
+		sum = 0;
+		for (j = 0; j < ETHTOOL_MAX_LANES; j++) {
+			if (values[i].per_lane[j] == ETHTOOL_STAT_NOT_SET)
+				break;
+			sum += values[i].per_lane[j];
+		}
+		if (nla_put_uint(skb, ETHTOOL_A_FEC_HIST_BIN_VAL,
+				 values[i].sum == ETHTOOL_STAT_NOT_SET ?
+				 sum : values[i].sum))
+			goto err_cancel_hist;
+		if (j && nla_put_64bit(skb, ETHTOOL_A_FEC_HIST_BIN_VAL_PER_LANE,
+				       sizeof(u64) * j,
+				       values[i].per_lane,
+				       ETHTOOL_A_FEC_HIST_PAD))
+			goto err_cancel_hist;
+
+		nla_nest_end(skb, nest);
+	}
+
+	return 0;
+
+err_cancel_hist:
+	nla_nest_cancel(skb, nest);
+	return -EMSGSIZE;
+}
+
+static int fec_put_stats(struct sk_buff *skb, const struct fec_reply_data *data)
+{
+	struct nlattr *nest;
+
+	nest = nla_nest_start(skb, ETHTOOL_A_FEC_STATS);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_64bit(skb, ETHTOOL_A_FEC_STAT_CORRECTED,
+			  sizeof(u64) * data->corr.cnt,
+			  data->corr.stats, ETHTOOL_A_FEC_STAT_PAD) ||
+	    nla_put_64bit(skb, ETHTOOL_A_FEC_STAT_UNCORR,
+			  sizeof(u64) * data->uncorr.cnt,
+			  data->uncorr.stats, ETHTOOL_A_FEC_STAT_PAD) ||
+	    nla_put_64bit(skb, ETHTOOL_A_FEC_STAT_CORR_BITS,
+			  sizeof(u64) * data->corr_bits.cnt,
+			  data->corr_bits.stats, ETHTOOL_A_FEC_STAT_PAD))
+		goto err_cancel;
+
+	if (fec_put_hist(skb, &data->fec_stat_hist))
+		goto err_cancel;
+
+	nla_nest_end(skb, nest);
+	return 0;
+
+err_cancel:
+	nla_nest_cancel(skb, nest);
+	return -EMSGSIZE;
+}
+
+static int fec_fill_reply(struct sk_buff *skb,
+			  const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	const struct fec_reply_data *data = FEC_REPDATA(reply_base);
+	int ret;
+
+	ret = ethnl_put_bitset(skb, ETHTOOL_A_FEC_MODES,
+			       data->fec_link_modes, NULL,
+			       __ETHTOOL_LINK_MODE_MASK_NBITS,
+			       link_mode_names, compact);
+	if (ret < 0)
+		return ret;
+
+	if (nla_put_u8(skb, ETHTOOL_A_FEC_AUTO, data->fec_auto) ||
+	    (data->active_fec &&
+	     nla_put_u32(skb, ETHTOOL_A_FEC_ACTIVE, data->active_fec)))
+		return -EMSGSIZE;
+
+	if (req_base->flags & ETHTOOL_FLAG_STATS && fec_put_stats(skb, data))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+/* FEC_SET */
+
+const struct nla_policy ethnl_fec_set_policy[ETHTOOL_A_FEC_AUTO + 1] = {
+	[ETHTOOL_A_FEC_HEADER]	= NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_FEC_MODES]	= { .type = NLA_NESTED },
+	[ETHTOOL_A_FEC_AUTO]	= NLA_POLICY_MAX(NLA_U8, 1),
+};
+
+static int
+ethnl_set_fec_validate(struct ethnl_req_info *req_info, struct genl_info *info)
+{
+	const struct ethtool_ops *ops = req_info->dev->ethtool_ops;
+
+	return ops->get_fecparam && ops->set_fecparam ? 1 : -EOPNOTSUPP;
+}
+
+static int
+ethnl_set_fec(struct ethnl_req_info *req_info, struct genl_info *info)
+{
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(fec_link_modes) = {};
+	struct net_device *dev = req_info->dev;
+	struct nlattr **tb = info->attrs;
+	struct ethtool_fecparam fec = {};
+	bool mod = false;
+	u8 fec_auto;
+	int ret;
+
+	ret = dev->ethtool_ops->get_fecparam(dev, &fec);
+	if (ret < 0)
+		return ret;
+
+	ethtool_fec_to_link_modes(fec.fec, fec_link_modes, &fec_auto);
+
+	ret = ethnl_update_bitset(fec_link_modes,
+				  __ETHTOOL_LINK_MODE_MASK_NBITS,
+				  tb[ETHTOOL_A_FEC_MODES],
+				  link_mode_names, info->extack, &mod);
+	if (ret < 0)
+		return ret;
+	ethnl_update_u8(&fec_auto, tb[ETHTOOL_A_FEC_AUTO], &mod);
+	if (!mod)
+		return 0;
+
+	ret = ethtool_link_modes_to_fecparam(&fec, fec_link_modes, fec_auto);
+	if (ret) {
+		NL_SET_ERR_MSG_ATTR(info->extack, tb[ETHTOOL_A_FEC_MODES],
+				    "invalid FEC modes requested");
+		return ret;
+	}
+	if (!fec.fec) {
+		NL_SET_ERR_MSG_ATTR(info->extack, tb[ETHTOOL_A_FEC_MODES],
+				    "no FEC modes set");
+		return -EINVAL;
+	}
+
+	ret = dev->ethtool_ops->set_fecparam(dev, &fec);
+	return ret < 0 ? ret : 1;
+}
+
+const struct ethnl_request_ops ethnl_fec_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_FEC_GET,
+	.reply_cmd		= ETHTOOL_MSG_FEC_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_FEC_HEADER,
+	.req_info_size		= sizeof(struct fec_req_info),
+	.reply_data_size	= sizeof(struct fec_reply_data),
+
+	.prepare_data		= fec_prepare_data,
+	.reply_size		= fec_reply_size,
+	.fill_reply		= fec_fill_reply,
+
+	.set_validate		= ethnl_set_fec_validate,
+	.set			= ethnl_set_fec,
+	.set_ntf_cmd		= ETHTOOL_MSG_FEC_NTF,
+};