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, 159 insertions, 0 deletions

diff --git a/drivers/media/common/ttpci-eeprom.c b/drivers/media/common/ttpci-eeprom.c
new file mode 100644
index 000000000..ef8746684
--- /dev/null
+++ b/drivers/media/common/ttpci-eeprom.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+    Retrieve encoded MAC address from 24C16 serial 2-wire EEPROM,
+    decode it and store it in the associated adapter struct for
+    use by dvb_net.c
+
+    This card appear to have the 24C16 write protect held to ground,
+    thus permitting normal read/write operation. Theoretically it
+    would be possible to write routines to burn a different (encoded)
+    MAC address into the EEPROM.
+
+    Robert Schlabbach	GMX
+    Michael Glaum	KVH Industries
+    Holger Waechtler	Convergence
+
+    Copyright (C) 2002-2003 Ralph Metzler <rjkm@metzlerbros.de>
+			    Metzler Brothers Systementwicklung GbR
+
+
+*/
+
+#include <asm/errno.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/i2c.h>
+#include <linux/etherdevice.h>
+
+#include "ttpci-eeprom.h"
+
+#if 1
+#define dprintk(x...) do { printk(x); } while (0)
+#else
+#define dprintk(x...) do { } while (0)
+#endif
+
+
+static int check_mac_tt(u8 *buf)
+{
+	int i;
+	u16 tmp = 0xffff;
+
+	for (i = 0; i < 8; i++) {
+		tmp  = (tmp << 8) | ((tmp >> 8) ^ buf[i]);
+		tmp ^= (tmp >> 4) & 0x0f;
+		tmp ^= (tmp << 12) ^ ((tmp & 0xff) << 5);
+	}
+	tmp ^= 0xffff;
+	return (((tmp >> 8) ^ buf[8]) | ((tmp & 0xff) ^ buf[9]));
+}
+
+static int getmac_tt(u8 * decodedMAC, u8 * encodedMAC)
+{
+	u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
+		       0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
+		       0x1d, 0x36, 0x64, 0x78};
+	u8 data[20];
+	int i;
+
+	/* In case there is a sig check failure have the orig contents available */
+	memcpy(data, encodedMAC, 20);
+
+	for (i = 0; i < 20; i++)
+		data[i] ^= xor[i];
+	for (i = 0; i < 10; i++)
+		data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
+			>> ((data[2 * i + 1] >> 6) & 3);
+
+	if (check_mac_tt(data))
+		return -ENODEV;
+
+	decodedMAC[0] = data[2]; decodedMAC[1] = data[1]; decodedMAC[2] = data[0];
+	decodedMAC[3] = data[6]; decodedMAC[4] = data[5]; decodedMAC[5] = data[4];
+	return 0;
+}
+
+int ttpci_eeprom_decode_mac(u8 *decodedMAC, u8 *encodedMAC)
+{
+	u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
+		       0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
+		       0x1d, 0x36, 0x64, 0x78};
+	u8 data[20];
+	int i;
+
+	memcpy(data, encodedMAC, 20);
+
+	for (i = 0; i < 20; i++)
+		data[i] ^= xor[i];
+	for (i = 0; i < 10; i++)
+		data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
+			>> ((data[2 * i + 1] >> 6) & 3);
+
+	if (check_mac_tt(data))
+		return -ENODEV;
+
+	decodedMAC[0] = data[2];
+	decodedMAC[1] = data[1];
+	decodedMAC[2] = data[0];
+	decodedMAC[3] = data[6];
+	decodedMAC[4] = data[5];
+	decodedMAC[5] = data[4];
+	return 0;
+}
+EXPORT_SYMBOL(ttpci_eeprom_decode_mac);
+
+static int ttpci_eeprom_read_encodedMAC(struct i2c_adapter *adapter, u8 * encodedMAC)
+{
+	int ret;
+	u8 b0[] = { 0xcc };
+
+	struct i2c_msg msg[] = {
+		{ .addr = 0x50, .flags = 0, .buf = b0, .len = 1 },
+		{ .addr = 0x50, .flags = I2C_M_RD, .buf = encodedMAC, .len = 20 }
+	};
+
+	/* dprintk("%s\n", __func__); */
+
+	ret = i2c_transfer(adapter, msg, 2);
+
+	if (ret != 2)		/* Assume EEPROM isn't there */
+		return (-ENODEV);
+
+	return 0;
+}
+
+
+int ttpci_eeprom_parse_mac(struct i2c_adapter *adapter, u8 *proposed_mac)
+{
+	int ret;
+	u8 encodedMAC[20];
+	u8 decodedMAC[6];
+
+	ret = ttpci_eeprom_read_encodedMAC(adapter, encodedMAC);
+
+	if (ret != 0) {		/* Will only be -ENODEV */
+		dprintk("Couldn't read from EEPROM: not there?\n");
+		eth_zero_addr(proposed_mac);
+		return ret;
+	}
+
+	ret = getmac_tt(decodedMAC, encodedMAC);
+	if( ret != 0 ) {
+		dprintk("adapter failed MAC signature check\n");
+		dprintk("encoded MAC from EEPROM was %*phC",
+			(int)sizeof(encodedMAC), &encodedMAC);
+		eth_zero_addr(proposed_mac);
+		return ret;
+	}
+
+	memcpy(proposed_mac, decodedMAC, 6);
+	dprintk("adapter has MAC addr = %pM\n", decodedMAC);
+	return 0;
+}
+
+EXPORT_SYMBOL(ttpci_eeprom_parse_mac);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Ralph Metzler, Marcus Metzler, others");
+MODULE_DESCRIPTION("Decode dvb_net MAC address from EEPROM of PCI DVB cards made by Siemens, Technotrend, Hauppauge");