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, 154 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/nettel.c b/arch/m68k/coldfire/nettel.c
new file mode 100644
index 000000000..e304571e0
--- /dev/null
+++ b/arch/m68k/coldfire/nettel.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0
+/***************************************************************************/
+
+/*
+ *	nettel.c -- startup code support for the NETtel boards
+ *
+ *	Copyright (C) 2009, Greg Ungerer (gerg@snapgear.com)
+ */
+
+/***************************************************************************/
+
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+#include <asm/nettel.h>
+
+/***************************************************************************/
+
+/*
+ * Define the IO and interrupt resources of the 2 SMC9196 interfaces.
+ */
+#define	NETTEL_SMC0_ADDR	0x30600300
+#define	NETTEL_SMC0_IRQ		29
+
+#define	NETTEL_SMC1_ADDR	0x30600000
+#define	NETTEL_SMC1_IRQ		27
+
+/*
+ * We need some access into the SMC9196 registers. Define those registers
+ * we will need here (including the smc91x.h doesn't seem to give us these
+ * in a simple form).
+ */
+#define	SMC91xx_BANKSELECT	14
+#define	SMC91xx_BASEADDR	2
+#define	SMC91xx_BASEMAC		4
+
+/***************************************************************************/
+
+static struct resource nettel_smc91x_0_resources[] = {
+	{
+		.start		= NETTEL_SMC0_ADDR,
+		.end		= NETTEL_SMC0_ADDR + 0x20,
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= NETTEL_SMC0_IRQ,
+		.end		= NETTEL_SMC0_IRQ,
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct resource nettel_smc91x_1_resources[] = {
+	{
+		.start		= NETTEL_SMC1_ADDR,
+		.end		= NETTEL_SMC1_ADDR + 0x20,
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= NETTEL_SMC1_IRQ,
+		.end		= NETTEL_SMC1_IRQ,
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct platform_device nettel_smc91x[] = {
+	{
+		.name			= "smc91x",
+		.id			= 0,
+		.num_resources		= ARRAY_SIZE(nettel_smc91x_0_resources),
+		.resource		= nettel_smc91x_0_resources,
+	},
+	{
+		.name			= "smc91x",
+		.id			= 1,
+		.num_resources		= ARRAY_SIZE(nettel_smc91x_1_resources),
+		.resource		= nettel_smc91x_1_resources,
+	},
+};
+
+static struct platform_device *nettel_devices[] __initdata = {
+	&nettel_smc91x[0],
+	&nettel_smc91x[1],
+};
+
+/***************************************************************************/
+
+static u8 nettel_macdefault[] __initdata = {
+	0x00, 0xd0, 0xcf, 0x00, 0x00, 0x01,
+};
+
+/*
+ * Set flash contained MAC address into SMC9196 core. Make sure the flash
+ * MAC address is sane, and not an empty flash. If no good use the Moreton
+ * Bay default MAC address instead.
+ */
+
+static void __init nettel_smc91x_setmac(unsigned int ioaddr, unsigned int flashaddr)
+{
+	u16 *macp;
+
+	macp = (u16 *) flashaddr;
+	if ((macp[0] == 0xffff) && (macp[1] == 0xffff) && (macp[2] == 0xffff))
+		macp = (u16 *) &nettel_macdefault[0];
+
+	mcf_write16(1, NETTEL_SMC0_ADDR + SMC91xx_BANKSELECT);
+	mcf_write16(macp[0], ioaddr + SMC91xx_BASEMAC);
+	mcf_write16(macp[1], ioaddr + SMC91xx_BASEMAC + 2);
+	mcf_write16(macp[2], ioaddr + SMC91xx_BASEMAC + 4);
+}
+
+/***************************************************************************/
+
+/*
+ * Re-map the address space of at least one of the SMC ethernet
+ * parts. Both parts power up decoding the same address, so we
+ * need to move one of them first, before doing anything else.
+ */
+
+static void __init nettel_smc91x_init(void)
+{
+	mcf_write16(0x00ec, MCFSIM_PADDR);
+	mcf_setppdata(0, 0x0080);
+	mcf_write16(1, NETTEL_SMC0_ADDR + SMC91xx_BANKSELECT);
+	mcf_write16(0x0067, NETTEL_SMC0_ADDR + SMC91xx_BASEADDR);
+	mcf_setppdata(0x0080, 0);
+
+	/* Set correct chip select timing for SMC9196 accesses */
+	mcf_write16(0x1180, MCFSIM_CSCR3);
+
+	/* Set the SMC interrupts to be auto-vectored */
+	mcf_autovector(NETTEL_SMC0_IRQ);
+	mcf_autovector(NETTEL_SMC1_IRQ);
+
+	/* Set MAC addresses from flash for both interfaces */
+	nettel_smc91x_setmac(NETTEL_SMC0_ADDR, 0xf0006000);
+	nettel_smc91x_setmac(NETTEL_SMC1_ADDR, 0xf0006006);
+}
+
+/***************************************************************************/
+
+static int __init init_nettel(void)
+{
+	nettel_smc91x_init();
+	platform_add_devices(nettel_devices, ARRAY_SIZE(nettel_devices));
+	return 0;
+}
+
+arch_initcall(init_nettel);
+
+/***************************************************************************/