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, 358 insertions, 0 deletions

diff --git a/drivers/net/phy/lxt.c b/drivers/net/phy/lxt.c
new file mode 100644
index 000000000..5251a61c8
--- /dev/null
+++ b/drivers/net/phy/lxt.c
@@ -0,0 +1,358 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * drivers/net/phy/lxt.c
+ *
+ * Driver for Intel LXT PHYs
+ *
+ * Author: Andy Fleming
+ *
+ * Copyright (c) 2004 Freescale Semiconductor, Inc.
+ */
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/unistd.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/skbuff.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mii.h>
+#include <linux/ethtool.h>
+#include <linux/phy.h>
+
+#include <asm/io.h>
+#include <asm/irq.h>
+#include <linux/uaccess.h>
+
+/* The Level one LXT970 is used by many boards				     */
+
+#define MII_LXT970_IER       17  /* Interrupt Enable Register */
+
+#define MII_LXT970_IER_IEN	0x0002
+
+#define MII_LXT970_ISR       18  /* Interrupt Status Register */
+
+#define MII_LXT970_IRS_MINT  BIT(15)
+
+#define MII_LXT970_CONFIG    19  /* Configuration Register    */
+
+/* ------------------------------------------------------------------------- */
+/* The Level one LXT971 is used on some of my custom boards                  */
+
+/* register definitions for the 971 */
+#define MII_LXT971_IER		18  /* Interrupt Enable Register */
+#define MII_LXT971_IER_IEN	0x00f2
+
+#define MII_LXT971_ISR		19  /* Interrupt Status Register */
+#define MII_LXT971_ISR_MASK	0x00f0
+
+/* register definitions for the 973 */
+#define MII_LXT973_PCR 16 /* Port Configuration Register */
+#define PCR_FIBER_SELECT 1
+
+MODULE_DESCRIPTION("Intel LXT PHY driver");
+MODULE_AUTHOR("Andy Fleming");
+MODULE_LICENSE("GPL");
+
+static int lxt970_ack_interrupt(struct phy_device *phydev)
+{
+	int err;
+
+	err = phy_read(phydev, MII_BMSR);
+
+	if (err < 0)
+		return err;
+
+	err = phy_read(phydev, MII_LXT970_ISR);
+
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static int lxt970_config_intr(struct phy_device *phydev)
+{
+	int err;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = lxt970_ack_interrupt(phydev);
+		if (err)
+			return err;
+
+		err = phy_write(phydev, MII_LXT970_IER, MII_LXT970_IER_IEN);
+	} else {
+		err = phy_write(phydev, MII_LXT970_IER, 0);
+		if (err)
+			return err;
+
+		err = lxt970_ack_interrupt(phydev);
+	}
+
+	return err;
+}
+
+static irqreturn_t lxt970_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	/* The interrupt status register is cleared by reading BMSR
+	 * followed by MII_LXT970_ISR
+	 */
+	irq_status = phy_read(phydev, MII_BMSR);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	irq_status = phy_read(phydev, MII_LXT970_ISR);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (!(irq_status & MII_LXT970_IRS_MINT))
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
+static int lxt970_config_init(struct phy_device *phydev)
+{
+	return phy_write(phydev, MII_LXT970_CONFIG, 0);
+}
+
+
+static int lxt971_ack_interrupt(struct phy_device *phydev)
+{
+	int err = phy_read(phydev, MII_LXT971_ISR);
+
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static int lxt971_config_intr(struct phy_device *phydev)
+{
+	int err;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = lxt971_ack_interrupt(phydev);
+		if (err)
+			return err;
+
+		err = phy_write(phydev, MII_LXT971_IER, MII_LXT971_IER_IEN);
+	} else {
+		err = phy_write(phydev, MII_LXT971_IER, 0);
+		if (err)
+			return err;
+
+		err = lxt971_ack_interrupt(phydev);
+	}
+
+	return err;
+}
+
+static irqreturn_t lxt971_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	irq_status = phy_read(phydev, MII_LXT971_ISR);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (!(irq_status & MII_LXT971_ISR_MASK))
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * A2 version of LXT973 chip has an ERRATA: it randomly return the contents
+ * of the previous even register when you read a odd register regularly
+ */
+
+static int lxt973a2_update_link(struct phy_device *phydev)
+{
+	int status;
+	int control;
+	int retry = 8; /* we try 8 times */
+
+	/* Do a fake read */
+	status = phy_read(phydev, MII_BMSR);
+
+	if (status < 0)
+		return status;
+
+	control = phy_read(phydev, MII_BMCR);
+	if (control < 0)
+		return control;
+
+	do {
+		/* Read link and autonegotiation status */
+		status = phy_read(phydev, MII_BMSR);
+	} while (status >= 0 && retry-- && status == control);
+
+	if (status < 0)
+		return status;
+
+	if ((status & BMSR_LSTATUS) == 0)
+		phydev->link = 0;
+	else
+		phydev->link = 1;
+
+	return 0;
+}
+
+static int lxt973a2_read_status(struct phy_device *phydev)
+{
+	int adv;
+	int err;
+	int lpa;
+
+	/* Update the link, but return if there was an error */
+	err = lxt973a2_update_link(phydev);
+	if (err)
+		return err;
+
+	if (AUTONEG_ENABLE == phydev->autoneg) {
+		int retry = 1;
+
+		adv = phy_read(phydev, MII_ADVERTISE);
+
+		if (adv < 0)
+			return adv;
+
+		do {
+			lpa = phy_read(phydev, MII_LPA);
+
+			if (lpa < 0)
+				return lpa;
+
+			/* If both registers are equal, it is suspect but not
+			 * impossible, hence a new try
+			 */
+		} while (lpa == adv && retry--);
+
+		mii_lpa_to_linkmode_lpa_t(phydev->lp_advertising, lpa);
+
+		lpa &= adv;
+
+		phydev->speed = SPEED_10;
+		phydev->duplex = DUPLEX_HALF;
+		phydev->pause = phydev->asym_pause = 0;
+
+		if (lpa & (LPA_100FULL | LPA_100HALF)) {
+			phydev->speed = SPEED_100;
+
+			if (lpa & LPA_100FULL)
+				phydev->duplex = DUPLEX_FULL;
+		} else {
+			if (lpa & LPA_10FULL)
+				phydev->duplex = DUPLEX_FULL;
+		}
+
+		phy_resolve_aneg_pause(phydev);
+	} else {
+		err = genphy_read_status_fixed(phydev);
+		if (err < 0)
+			return err;
+
+		phydev->pause = phydev->asym_pause = 0;
+		linkmode_zero(phydev->lp_advertising);
+	}
+
+	return 0;
+}
+
+static int lxt973_probe(struct phy_device *phydev)
+{
+	int val = phy_read(phydev, MII_LXT973_PCR);
+
+	if (val & PCR_FIBER_SELECT) {
+		/*
+		 * If fiber is selected, then the only correct setting
+		 * is 100Mbps, full duplex, and auto negotiation off.
+		 */
+		val = phy_read(phydev, MII_BMCR);
+		val |= (BMCR_SPEED100 | BMCR_FULLDPLX);
+		val &= ~BMCR_ANENABLE;
+		phy_write(phydev, MII_BMCR, val);
+		/* Remember that the port is in fiber mode. */
+		phydev->priv = lxt973_probe;
+		phydev->port = PORT_FIBRE;
+	} else {
+		phydev->priv = NULL;
+	}
+	return 0;
+}
+
+static int lxt973_config_aneg(struct phy_device *phydev)
+{
+	/* Do nothing if port is in fiber mode. */
+	return phydev->priv ? 0 : genphy_config_aneg(phydev);
+}
+
+static struct phy_driver lxt97x_driver[] = {
+{
+	.phy_id		= 0x78100000,
+	.name		= "LXT970",
+	.phy_id_mask	= 0xfffffff0,
+	/* PHY_BASIC_FEATURES */
+	.config_init	= lxt970_config_init,
+	.config_intr	= lxt970_config_intr,
+	.handle_interrupt = lxt970_handle_interrupt,
+}, {
+	.phy_id		= 0x001378e0,
+	.name		= "LXT971",
+	.phy_id_mask	= 0xfffffff0,
+	/* PHY_BASIC_FEATURES */
+	.config_intr	= lxt971_config_intr,
+	.handle_interrupt = lxt971_handle_interrupt,
+	.suspend	= genphy_suspend,
+	.resume		= genphy_resume,
+}, {
+	.phy_id		= 0x00137a10,
+	.name		= "LXT973-A2",
+	.phy_id_mask	= 0xffffffff,
+	/* PHY_BASIC_FEATURES */
+	.flags		= 0,
+	.probe		= lxt973_probe,
+	.config_aneg	= lxt973_config_aneg,
+	.read_status	= lxt973a2_read_status,
+	.suspend	= genphy_suspend,
+	.resume		= genphy_resume,
+}, {
+	.phy_id		= 0x00137a10,
+	.name		= "LXT973",
+	.phy_id_mask	= 0xfffffff0,
+	/* PHY_BASIC_FEATURES */
+	.flags		= 0,
+	.probe		= lxt973_probe,
+	.config_aneg	= lxt973_config_aneg,
+	.suspend	= genphy_suspend,
+	.resume		= genphy_resume,
+} };
+
+module_phy_driver(lxt97x_driver);
+
+static const struct mdio_device_id __maybe_unused lxt_tbl[] = {
+	{ 0x78100000, 0xfffffff0 },
+	{ 0x001378e0, 0xfffffff0 },
+	{ 0x00137a10, 0xfffffff0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, lxt_tbl);