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, 286 insertions, 0 deletions

diff --git a/net/mac80211/tests/mfp.c b/net/mac80211/tests/mfp.c
new file mode 100644
index 000000000..58e675e0e
--- /dev/null
+++ b/net/mac80211/tests/mfp.c
@@ -0,0 +1,286 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for management frame acceptance
+ *
+ * Copyright (C) 2023 Intel Corporation
+ */
+#include <kunit/test.h>
+#include <kunit/skbuff.h>
+#include "../ieee80211_i.h"
+#include "../sta_info.h"
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+static const struct mfp_test_case {
+	const char *desc;
+	bool sta, mfp, decrypted, unicast, assoc;
+	u8 category;
+	u8 stype;
+	u8 action;
+	ieee80211_rx_result result;
+} accept_mfp_cases[] = {
+	/* regular public action */
+	{
+		.desc = "public action: accept unicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: accept multicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: accept unicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: accept multicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: drop unicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_UNICAST_PUB_ACTION,
+	},
+	{
+		.desc = "public action: accept multicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.mfp = true,
+		.result = RX_CONTINUE,
+	},
+	/* protected dual of public action */
+	{
+		.desc = "protected dual: drop unicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop multicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop unicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop multicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop undecrypted unicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop undecrypted multicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: accept unicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.decrypted = true,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "protected dual: accept multicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.decrypted = true,
+		.unicast = false,
+		.sta = true,
+		.mfp = true,
+		.result = RX_CONTINUE,
+	},
+	/* deauth/disassoc before keys are set */
+	{
+		.desc = "deauth: accept unicast with MFP but w/o key",
+		.stype = IEEE80211_STYPE_DEAUTH,
+		.sta = true,
+		.mfp = true,
+		.unicast = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "disassoc: accept unicast with MFP but w/o key",
+		.stype = IEEE80211_STYPE_DEAUTH,
+		.sta = true,
+		.mfp = true,
+		.unicast = true,
+		.result = RX_CONTINUE,
+	},
+	/* non-public robust action frame ... */
+	{
+		.desc = "BA action: drop unicast before assoc",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.result = RX_DROP_U_UNPROT_ROBUST_ACTION,
+	},
+	{
+		.desc = "BA action: drop unprotected after assoc",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_UCAST_MGMT,
+	},
+	{
+		.desc = "BA action: accept unprotected without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.assoc = true,
+		.mfp = false,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "BA action: drop unprotected with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_UCAST_MGMT,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(accept_mfp, accept_mfp_cases, desc);
+
+static void accept_mfp(struct kunit *test)
+{
+	static struct sta_info sta;
+	const struct mfp_test_case *params = test->param_value;
+	struct ieee80211_rx_data rx = {
+		.sta = params->sta ? &sta : NULL,
+	};
+	struct ieee80211_rx_status *status;
+	struct ieee80211_hdr_3addr hdr = {
+		.frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
+					     params->stype),
+		.addr1 = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
+		.addr2 = { 0x12, 0x22, 0x33, 0x44, 0x55, 0x66 },
+		/* A3/BSSID doesn't matter here */
+	};
+
+	memset(&sta, 0, sizeof(sta));
+
+	if (!params->sta) {
+		KUNIT_ASSERT_FALSE(test, params->mfp);
+		KUNIT_ASSERT_FALSE(test, params->decrypted);
+	}
+
+	if (params->mfp)
+		set_sta_flag(&sta, WLAN_STA_MFP);
+
+	if (params->assoc)
+		set_bit(WLAN_STA_ASSOC, &sta._flags);
+
+	rx.skb = kunit_zalloc_skb(test, 128, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, rx.skb);
+	status = IEEE80211_SKB_RXCB(rx.skb);
+
+	if (params->decrypted) {
+		status->flag |= RX_FLAG_DECRYPTED;
+		if (params->unicast)
+			hdr.frame_control |=
+				cpu_to_le16(IEEE80211_FCTL_PROTECTED);
+	}
+
+	if (params->unicast)
+		hdr.addr1[0] = 0x02;
+
+	skb_put_data(rx.skb, &hdr, sizeof(hdr));
+
+	switch (params->stype) {
+	case IEEE80211_STYPE_ACTION:
+		skb_put_u8(rx.skb, params->category);
+		skb_put_u8(rx.skb, params->action);
+		break;
+	case IEEE80211_STYPE_DEAUTH:
+	case IEEE80211_STYPE_DISASSOC: {
+		__le16 reason = cpu_to_le16(WLAN_REASON_UNSPECIFIED);
+
+		skb_put_data(rx.skb, &reason, sizeof(reason));
+		}
+		break;
+	}
+
+	KUNIT_EXPECT_EQ(test,
+			(__force u32)ieee80211_drop_unencrypted_mgmt(&rx),
+			(__force u32)params->result);
+}
+
+static struct kunit_case mfp_test_cases[] = {
+	KUNIT_CASE_PARAM(accept_mfp, accept_mfp_gen_params),
+	{}
+};
+
+static struct kunit_suite mfp = {
+	.name = "mac80211-mfp",
+	.test_cases = mfp_test_cases,
+};
+
+kunit_test_suite(mfp);