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, 128 insertions, 0 deletions

diff --git a/arch/mips/ath25/devices.c b/arch/mips/ath25/devices.c
new file mode 100644
index 000000000..301a90282
--- /dev/null
+++ b/arch/mips/ath25/devices.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/serial_8250.h>
+#include <linux/platform_device.h>
+#include <asm/bootinfo.h>
+
+#include <ath25_platform.h>
+#include "devices.h"
+#include "ar5312.h"
+#include "ar2315.h"
+
+struct ar231x_board_config ath25_board;
+enum ath25_soc_type ath25_soc = ATH25_SOC_UNKNOWN;
+
+static struct resource ath25_wmac0_res[] = {
+	{
+		.name = "wmac0_membase",
+		.flags = IORESOURCE_MEM,
+	},
+	{
+		.name = "wmac0_irq",
+		.flags = IORESOURCE_IRQ,
+	}
+};
+
+static struct resource ath25_wmac1_res[] = {
+	{
+		.name = "wmac1_membase",
+		.flags = IORESOURCE_MEM,
+	},
+	{
+		.name = "wmac1_irq",
+		.flags = IORESOURCE_IRQ,
+	}
+};
+
+static struct platform_device ath25_wmac[] = {
+	{
+		.id = 0,
+		.name = "ar231x-wmac",
+		.resource = ath25_wmac0_res,
+		.num_resources = ARRAY_SIZE(ath25_wmac0_res),
+		.dev.platform_data = &ath25_board,
+	},
+	{
+		.id = 1,
+		.name = "ar231x-wmac",
+		.resource = ath25_wmac1_res,
+		.num_resources = ARRAY_SIZE(ath25_wmac1_res),
+		.dev.platform_data = &ath25_board,
+	},
+};
+
+static const char * const soc_type_strings[] = {
+	[ATH25_SOC_AR5312] = "Atheros AR5312",
+	[ATH25_SOC_AR2312] = "Atheros AR2312",
+	[ATH25_SOC_AR2313] = "Atheros AR2313",
+	[ATH25_SOC_AR2315] = "Atheros AR2315",
+	[ATH25_SOC_AR2316] = "Atheros AR2316",
+	[ATH25_SOC_AR2317] = "Atheros AR2317",
+	[ATH25_SOC_AR2318] = "Atheros AR2318",
+	[ATH25_SOC_UNKNOWN] = "Atheros (unknown)",
+};
+
+const char *get_system_type(void)
+{
+	if ((ath25_soc >= ARRAY_SIZE(soc_type_strings)) ||
+	    !soc_type_strings[ath25_soc])
+		return soc_type_strings[ATH25_SOC_UNKNOWN];
+	return soc_type_strings[ath25_soc];
+}
+
+void __init ath25_serial_setup(u32 mapbase, int irq, unsigned int uartclk)
+{
+#ifdef CONFIG_SERIAL_8250_CONSOLE
+	struct uart_port s;
+
+	memset(&s, 0, sizeof(s));
+
+	s.flags = UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_IOREMAP;
+	s.iotype = UPIO_MEM32;
+	s.irq = irq;
+	s.regshift = 2;
+	s.mapbase = mapbase;
+	s.uartclk = uartclk;
+
+	early_serial_setup(&s);
+#endif /* CONFIG_SERIAL_8250_CONSOLE */
+}
+
+int __init ath25_add_wmac(int nr, u32 base, int irq)
+{
+	struct resource *res;
+
+	ath25_wmac[nr].dev.platform_data = &ath25_board;
+	res = &ath25_wmac[nr].resource[0];
+	res->start = base;
+	res->end = base + 0x10000 - 1;
+	res++;
+	res->start = irq;
+	res->end = irq;
+	return platform_device_register(&ath25_wmac[nr]);
+}
+
+static int __init ath25_register_devices(void)
+{
+	if (is_ar5312())
+		ar5312_init_devices();
+	else
+		ar2315_init_devices();
+
+	return 0;
+}
+
+device_initcall(ath25_register_devices);
+
+static int __init ath25_arch_init(void)
+{
+	if (is_ar5312())
+		ar5312_arch_init();
+	else
+		ar2315_arch_init();
+
+	return 0;
+}
+
+arch_initcall(ath25_arch_init);