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, 284 insertions, 0 deletions

diff --git a/net/mac80211/tests/tpe.c b/net/mac80211/tests/tpe.c
new file mode 100644
index 000000000..c73b6c66b
--- /dev/null
+++ b/net/mac80211/tests/tpe.c
@@ -0,0 +1,284 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for TPE element handling
+ *
+ * Copyright (C) 2024 Intel Corporation
+ */
+#include <kunit/test.h>
+#include "../ieee80211_i.h"
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+static struct ieee80211_channel chan6g_1 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 5955,
+};
+
+static struct ieee80211_channel chan6g_33 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 6115,
+};
+
+static struct ieee80211_channel chan6g_61 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 6255,
+};
+
+static const struct subchan_test_case {
+	const char *desc;
+	struct cfg80211_chan_def c;
+	u8 n;
+	int expect;
+} subchan_offset_cases[] = {
+	{
+		.desc = "identical 20 MHz",
+		.c.width = NL80211_CHAN_WIDTH_20,
+		.c.chan = &chan6g_1,
+		.c.center_freq1 = 5955,
+		.n = 1,
+		.expect = 0,
+	},
+	{
+		.desc = "identical 40 MHz",
+		.c.width = NL80211_CHAN_WIDTH_40,
+		.c.chan = &chan6g_1,
+		.c.center_freq1 = 5965,
+		.n = 2,
+		.expect = 0,
+	},
+	{
+		.desc = "identical 80+80 MHz",
+		/* not really is valid? doesn't matter for the test */
+		.c.width = NL80211_CHAN_WIDTH_80P80,
+		.c.chan = &chan6g_1,
+		.c.center_freq1 = 5985,
+		.c.center_freq2 = 6225,
+		.n = 16,
+		.expect = 0,
+	},
+	{
+		.desc = "identical 320 MHz",
+		.c.width = NL80211_CHAN_WIDTH_320,
+		.c.chan = &chan6g_1,
+		.c.center_freq1 = 6105,
+		.n = 16,
+		.expect = 0,
+	},
+	{
+		.desc = "lower 160 MHz of 320 MHz",
+		.c.width = NL80211_CHAN_WIDTH_320,
+		.c.chan = &chan6g_1,
+		.c.center_freq1 = 6105,
+		.n = 8,
+		.expect = 0,
+	},
+	{
+		.desc = "upper 160 MHz of 320 MHz",
+		.c.width = NL80211_CHAN_WIDTH_320,
+		.c.chan = &chan6g_61,
+		.c.center_freq1 = 6105,
+		.n = 8,
+		.expect = 8,
+	},
+	{
+		.desc = "upper 160 MHz of 320 MHz, go to 40",
+		.c.width = NL80211_CHAN_WIDTH_320,
+		.c.chan = &chan6g_61,
+		.c.center_freq1 = 6105,
+		.n = 2,
+		.expect = 8 + 4 + 2,
+	},
+	{
+		.desc = "secondary 80 above primary in 80+80 MHz",
+		/* not really is valid? doesn't matter for the test */
+		.c.width = NL80211_CHAN_WIDTH_80P80,
+		.c.chan = &chan6g_1,
+		.c.center_freq1 = 5985,
+		.c.center_freq2 = 6225,
+		.n = 4,
+		.expect = 0,
+	},
+	{
+		.desc = "secondary 80 below primary in 80+80 MHz",
+		/* not really is valid? doesn't matter for the test */
+		.c.width = NL80211_CHAN_WIDTH_80P80,
+		.c.chan = &chan6g_61,
+		.c.center_freq1 = 6225,
+		.c.center_freq2 = 5985,
+		.n = 4,
+		.expect = 4,
+	},
+	{
+		.desc = "secondary 80 below primary in 80+80 MHz, go to 20",
+		/* not really is valid? doesn't matter for the test */
+		.c.width = NL80211_CHAN_WIDTH_80P80,
+		.c.chan = &chan6g_61,
+		.c.center_freq1 = 6225,
+		.c.center_freq2 = 5985,
+		.n = 1,
+		.expect = 7,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(subchan_offset, subchan_offset_cases, desc);
+
+static void subchan_offset(struct kunit *test)
+{
+	const struct subchan_test_case *params = test->param_value;
+	int offset;
+
+	KUNIT_ASSERT_EQ(test, cfg80211_chandef_valid(&params->c), true);
+
+	offset = ieee80211_calc_chandef_subchan_offset(&params->c, params->n);
+
+	KUNIT_EXPECT_EQ(test, params->expect, offset);
+}
+
+static const struct psd_reorder_test_case {
+	const char *desc;
+	struct cfg80211_chan_def ap, used;
+	struct ieee80211_parsed_tpe_psd psd, out;
+} psd_reorder_cases[] = {
+	{
+		.desc = "no changes, 320 MHz",
+
+		.ap.width = NL80211_CHAN_WIDTH_320,
+		.ap.chan = &chan6g_1,
+		.ap.center_freq1 = 6105,
+
+		.used.width = NL80211_CHAN_WIDTH_320,
+		.used.chan = &chan6g_1,
+		.used.center_freq1 = 6105,
+
+		.psd.valid = true,
+		.psd.count = 16,
+		.psd.n = 8,
+		.psd.power = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+
+		.out.valid = true,
+		.out.count = 16,
+		.out.n = 8,
+		.out.power = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+	},
+	{
+		.desc = "no changes, 320 MHz, 160 MHz used, n=0",
+
+		.ap.width = NL80211_CHAN_WIDTH_320,
+		.ap.chan = &chan6g_1,
+		.ap.center_freq1 = 6105,
+
+		.used.width = NL80211_CHAN_WIDTH_160,
+		.used.chan = &chan6g_1,
+		.used.center_freq1 = 6025,
+
+		.psd.valid = true,
+		.psd.count = 16,
+		.psd.n = 0,
+		.psd.power = { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, },
+
+		.out.valid = true,
+		.out.count = 8,
+		.out.n = 0,
+		.out.power = { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, },
+	},
+	{
+		.desc = "320 MHz, HE is 80, used 160, all lower",
+
+		.ap.width = NL80211_CHAN_WIDTH_320,
+		.ap.chan = &chan6g_1,
+		.ap.center_freq1 = 6105,
+
+		.used.width = NL80211_CHAN_WIDTH_160,
+		.used.chan = &chan6g_1,
+		.used.center_freq1 = 6025,
+
+		.psd.valid = true,
+		.psd.count = 16,
+		.psd.n = 4,
+		.psd.power = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+
+		.out.valid = true,
+		.out.count = 8,
+		.out.n = 4,
+		.out.power = { 0, 1, 2, 3, 4, 5, 6, 7, 127, 127, 127, 127, 127, 127, 127, 127},
+	},
+	{
+		.desc = "320 MHz, HE is 80, used 160, all upper",
+		/*
+		 * EHT: | | | | | | | | | | | | | | | | |
+		 * HE:                          | | | | |
+		 * used:                | | | | | | | | |
+		 */
+
+		.ap.width = NL80211_CHAN_WIDTH_320,
+		.ap.chan = &chan6g_61,
+		.ap.center_freq1 = 6105,
+
+		.used.width = NL80211_CHAN_WIDTH_160,
+		.used.chan = &chan6g_61,
+		.used.center_freq1 = 6185,
+
+		.psd.valid = true,
+		.psd.count = 16,
+		.psd.n = 4,
+		.psd.power = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+
+		.out.valid = true,
+		.out.count = 8,
+		.out.n = 4,
+		.out.power = { 12, 13, 14, 15, 0, 1, 2, 3, 127, 127, 127, 127, 127, 127, 127, 127},
+	},
+	{
+		.desc = "320 MHz, HE is 80, used 160, split",
+		/*
+		 * EHT: | | | | | | | | | | | | | | | | |
+		 * HE:                  | | | | |
+		 * used:                | | | | | | | | |
+		 */
+
+		.ap.width = NL80211_CHAN_WIDTH_320,
+		.ap.chan = &chan6g_33,
+		.ap.center_freq1 = 6105,
+
+		.used.width = NL80211_CHAN_WIDTH_160,
+		.used.chan = &chan6g_33,
+		.used.center_freq1 = 6185,
+
+		.psd.valid = true,
+		.psd.count = 16,
+		.psd.n = 4,
+		.psd.power = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+
+		.out.valid = true,
+		.out.count = 8,
+		.out.n = 4,
+		.out.power = { 0, 1, 2, 3, 12, 13, 14, 15, 127, 127, 127, 127, 127, 127, 127, 127},
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(psd_reorder, psd_reorder_cases, desc);
+
+static void psd_reorder(struct kunit *test)
+{
+	const struct psd_reorder_test_case *params = test->param_value;
+	struct ieee80211_parsed_tpe_psd tmp = params->psd;
+
+	KUNIT_ASSERT_EQ(test, cfg80211_chandef_valid(&params->ap), true);
+	KUNIT_ASSERT_EQ(test, cfg80211_chandef_valid(&params->used), true);
+
+	ieee80211_rearrange_tpe_psd(&tmp, &params->ap, &params->used);
+	KUNIT_EXPECT_MEMEQ(test, &tmp, &params->out, sizeof(tmp));
+}
+
+static struct kunit_case tpe_test_cases[] = {
+	KUNIT_CASE_PARAM(subchan_offset, subchan_offset_gen_params),
+	KUNIT_CASE_PARAM(psd_reorder, psd_reorder_gen_params),
+	{}
+};
+
+static struct kunit_suite tpe = {
+	.name = "mac80211-tpe",
+	.test_cases = tpe_test_cases,
+};
+
+kunit_test_suite(tpe);