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, 222 insertions, 0 deletions

diff --git a/net/ethtool/pause.c b/net/ethtool/pause.c
new file mode 100644
index 000000000..ccaec8e87
--- /dev/null
+++ b/net/ethtool/pause.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "common.h"
+#include "netlink.h"
+
+struct pause_req_info {
+	struct ethnl_req_info		base;
+	enum ethtool_mac_stats_src	src;
+};
+
+#define PAUSE_REQINFO(__req_base) \
+	container_of(__req_base, struct pause_req_info, base)
+
+struct pause_reply_data {
+	struct ethnl_reply_data		base;
+	struct ethtool_pauseparam	pauseparam;
+	struct ethtool_pause_stats	pausestat;
+};
+
+#define PAUSE_REPDATA(__reply_base) \
+	container_of(__reply_base, struct pause_reply_data, base)
+
+const struct nla_policy ethnl_pause_get_policy[] = {
+	[ETHTOOL_A_PAUSE_HEADER]		=
+		NLA_POLICY_NESTED(ethnl_header_policy_stats),
+	[ETHTOOL_A_PAUSE_STATS_SRC]		=
+		NLA_POLICY_MAX(NLA_U32, ETHTOOL_MAC_STATS_SRC_PMAC),
+};
+
+static int pause_parse_request(struct ethnl_req_info *req_base,
+			       const struct genl_info *info,
+			       struct nlattr **tb,
+			       struct netlink_ext_ack *extack)
+{
+	enum ethtool_mac_stats_src src = ETHTOOL_MAC_STATS_SRC_AGGREGATE;
+	struct pause_req_info *req_info = PAUSE_REQINFO(req_base);
+
+	if (tb[ETHTOOL_A_PAUSE_STATS_SRC]) {
+		if (!(req_base->flags & ETHTOOL_FLAG_STATS)) {
+			NL_SET_ERR_MSG_MOD(extack,
+					   "ETHTOOL_FLAG_STATS must be set when requesting a source of stats");
+			return -EINVAL;
+		}
+
+		src = nla_get_u32(tb[ETHTOOL_A_PAUSE_STATS_SRC]);
+	}
+
+	req_info->src = src;
+
+	return 0;
+}
+
+static int pause_prepare_data(const struct ethnl_req_info *req_base,
+			      struct ethnl_reply_data *reply_base,
+			      const struct genl_info *info)
+{
+	const struct pause_req_info *req_info = PAUSE_REQINFO(req_base);
+	struct pause_reply_data *data = PAUSE_REPDATA(reply_base);
+	enum ethtool_mac_stats_src src = req_info->src;
+	struct net_device *dev = reply_base->dev;
+	int ret;
+
+	if (!dev->ethtool_ops->get_pauseparam)
+		return -EOPNOTSUPP;
+
+	ethtool_stats_init((u64 *)&data->pausestat,
+			   sizeof(data->pausestat) / 8);
+	data->pausestat.src = src;
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		return ret;
+
+	if ((src == ETHTOOL_MAC_STATS_SRC_EMAC ||
+	     src == ETHTOOL_MAC_STATS_SRC_PMAC) &&
+	    !__ethtool_dev_mm_supported(dev)) {
+		NL_SET_ERR_MSG_MOD(info->extack,
+				   "Device does not support MAC merge layer");
+		ethnl_ops_complete(dev);
+		return -EOPNOTSUPP;
+	}
+
+	dev->ethtool_ops->get_pauseparam(dev, &data->pauseparam);
+	if (req_base->flags & ETHTOOL_FLAG_STATS &&
+	    dev->ethtool_ops->get_pause_stats)
+		dev->ethtool_ops->get_pause_stats(dev, &data->pausestat);
+
+	ethnl_ops_complete(dev);
+
+	return 0;
+}
+
+static int pause_reply_size(const struct ethnl_req_info *req_base,
+			    const struct ethnl_reply_data *reply_base)
+{
+	int n = nla_total_size(sizeof(u8)) +	/* _PAUSE_AUTONEG */
+		nla_total_size(sizeof(u8)) +	/* _PAUSE_RX */
+		nla_total_size(sizeof(u8));	/* _PAUSE_TX */
+
+	if (req_base->flags & ETHTOOL_FLAG_STATS)
+		n += nla_total_size(0) +	/* _PAUSE_STATS */
+		     nla_total_size(sizeof(u32)) + /* _PAUSE_STATS_SRC */
+		     nla_total_size_64bit(sizeof(u64)) * ETHTOOL_PAUSE_STAT_CNT;
+	return n;
+}
+
+static int ethtool_put_stat(struct sk_buff *skb, u64 val, u16 attrtype,
+			    u16 padtype)
+{
+	if (val == ETHTOOL_STAT_NOT_SET)
+		return 0;
+	if (nla_put_u64_64bit(skb, attrtype, val, padtype))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static int pause_put_stats(struct sk_buff *skb,
+			   const struct ethtool_pause_stats *pause_stats)
+{
+	const u16 pad = ETHTOOL_A_PAUSE_STAT_PAD;
+	struct nlattr *nest;
+
+	if (nla_put_u32(skb, ETHTOOL_A_PAUSE_STATS_SRC, pause_stats->src))
+		return -EMSGSIZE;
+
+	nest = nla_nest_start(skb, ETHTOOL_A_PAUSE_STATS);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (ethtool_put_stat(skb, pause_stats->tx_pause_frames,
+			     ETHTOOL_A_PAUSE_STAT_TX_FRAMES, pad) ||
+	    ethtool_put_stat(skb, pause_stats->rx_pause_frames,
+			     ETHTOOL_A_PAUSE_STAT_RX_FRAMES, pad) ||
+	    ethtool_put_stat(skb, pause_stats->tx_pause_storm_events,
+			     ETHTOOL_A_PAUSE_STAT_TX_PAUSE_STORM_EVENTS, pad))
+		goto err_cancel;
+
+	nla_nest_end(skb, nest);
+	return 0;
+
+err_cancel:
+	nla_nest_cancel(skb, nest);
+	return -EMSGSIZE;
+}
+
+static int pause_fill_reply(struct sk_buff *skb,
+			    const struct ethnl_req_info *req_base,
+			    const struct ethnl_reply_data *reply_base)
+{
+	const struct pause_reply_data *data = PAUSE_REPDATA(reply_base);
+	const struct ethtool_pauseparam *pauseparam = &data->pauseparam;
+
+	if (nla_put_u8(skb, ETHTOOL_A_PAUSE_AUTONEG, !!pauseparam->autoneg) ||
+	    nla_put_u8(skb, ETHTOOL_A_PAUSE_RX, !!pauseparam->rx_pause) ||
+	    nla_put_u8(skb, ETHTOOL_A_PAUSE_TX, !!pauseparam->tx_pause))
+		return -EMSGSIZE;
+
+	if (req_base->flags & ETHTOOL_FLAG_STATS &&
+	    pause_put_stats(skb, &data->pausestat))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+/* PAUSE_SET */
+
+const struct nla_policy ethnl_pause_set_policy[] = {
+	[ETHTOOL_A_PAUSE_HEADER]		=
+		NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_PAUSE_AUTONEG]		= { .type = NLA_U8 },
+	[ETHTOOL_A_PAUSE_RX]			= { .type = NLA_U8 },
+	[ETHTOOL_A_PAUSE_TX]			= { .type = NLA_U8 },
+	[ETHTOOL_A_PAUSE_STATS_SRC]		= { .type = NLA_REJECT },
+};
+
+static int
+ethnl_set_pause_validate(struct ethnl_req_info *req_info,
+			 struct genl_info *info)
+{
+	const struct ethtool_ops *ops = req_info->dev->ethtool_ops;
+
+	return ops->get_pauseparam && ops->set_pauseparam ? 1 : -EOPNOTSUPP;
+}
+
+static int
+ethnl_set_pause(struct ethnl_req_info *req_info, struct genl_info *info)
+{
+	struct net_device *dev = req_info->dev;
+	struct ethtool_pauseparam params = {};
+	struct nlattr **tb = info->attrs;
+	bool mod = false;
+	int ret;
+
+	dev->ethtool_ops->get_pauseparam(dev, &params);
+
+	ethnl_update_bool32(&params.autoneg, tb[ETHTOOL_A_PAUSE_AUTONEG], &mod);
+	ethnl_update_bool32(&params.rx_pause, tb[ETHTOOL_A_PAUSE_RX], &mod);
+	ethnl_update_bool32(&params.tx_pause, tb[ETHTOOL_A_PAUSE_TX], &mod);
+	if (!mod)
+		return 0;
+
+	ret = dev->ethtool_ops->set_pauseparam(dev, &params);
+	return ret < 0 ? ret : 1;
+}
+
+const struct ethnl_request_ops ethnl_pause_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_PAUSE_GET,
+	.reply_cmd		= ETHTOOL_MSG_PAUSE_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_PAUSE_HEADER,
+	.req_info_size		= sizeof(struct pause_req_info),
+	.reply_data_size	= sizeof(struct pause_reply_data),
+
+	.parse_request		= pause_parse_request,
+	.prepare_data		= pause_prepare_data,
+	.reply_size		= pause_reply_size,
+	.fill_reply		= pause_fill_reply,
+
+	.set_validate		= ethnl_set_pause_validate,
+	.set			= ethnl_set_pause,
+	.set_ntf_cmd		= ETHTOOL_MSG_PAUSE_NTF,
+};