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, 222 insertions, 0 deletions

diff --git a/drivers/net/phy/bcm87xx.c b/drivers/net/phy/bcm87xx.c
new file mode 100644
index 000000000..299f9a8f3
--- /dev/null
+++ b/drivers/net/phy/bcm87xx.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2011 - 2012 Cavium, Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/phy.h>
+#include <linux/of.h>
+
+#define PHY_ID_BCM8706	0x0143bdc1
+#define PHY_ID_BCM8727	0x0143bff0
+
+#define BCM87XX_PMD_RX_SIGNAL_DETECT	0x000a
+#define BCM87XX_10GBASER_PCS_STATUS	0x0020
+#define BCM87XX_XGXS_LANE_STATUS	0x0018
+
+#define BCM87XX_LASI_CONTROL		0x9002
+#define BCM87XX_LASI_STATUS		0x9005
+
+#if IS_ENABLED(CONFIG_OF_MDIO)
+/* Set and/or override some configuration registers based on the
+ * broadcom,c45-reg-init property stored in the of_node for the phydev.
+ *
+ * broadcom,c45-reg-init = <devid reg mask value>,...;
+ *
+ * There may be one or more sets of <devid reg mask value>:
+ *
+ * devid: which sub-device to use.
+ * reg: the register.
+ * mask: if non-zero, ANDed with existing register value.
+ * value: ORed with the masked value and written to the regiser.
+ *
+ */
+static int bcm87xx_of_reg_init(struct phy_device *phydev)
+{
+	const __be32 *paddr;
+	const __be32 *paddr_end;
+	int len, ret;
+
+	if (!phydev->mdio.dev.of_node)
+		return 0;
+
+	paddr = of_get_property(phydev->mdio.dev.of_node,
+				"broadcom,c45-reg-init", &len);
+	if (!paddr)
+		return 0;
+
+	paddr_end = paddr + (len /= sizeof(*paddr));
+
+	ret = 0;
+
+	while (paddr + 3 < paddr_end) {
+		u16 devid	= be32_to_cpup(paddr++);
+		u16 reg		= be32_to_cpup(paddr++);
+		u16 mask	= be32_to_cpup(paddr++);
+		u16 val_bits	= be32_to_cpup(paddr++);
+		int val = 0;
+
+		if (mask) {
+			val = phy_read_mmd(phydev, devid, reg);
+			if (val < 0) {
+				ret = val;
+				goto err;
+			}
+			val &= mask;
+		}
+		val |= val_bits;
+
+		ret = phy_write_mmd(phydev, devid, reg, val);
+		if (ret < 0)
+			goto err;
+	}
+err:
+	return ret;
+}
+#else
+static int bcm87xx_of_reg_init(struct phy_device *phydev)
+{
+	return 0;
+}
+#endif /* CONFIG_OF_MDIO */
+
+static int bcm87xx_get_features(struct phy_device *phydev)
+{
+	linkmode_set_bit(ETHTOOL_LINK_MODE_10000baseR_FEC_BIT,
+			 phydev->supported);
+	return 0;
+}
+
+static int bcm87xx_config_init(struct phy_device *phydev)
+{
+	return bcm87xx_of_reg_init(phydev);
+}
+
+static int bcm87xx_config_aneg(struct phy_device *phydev)
+{
+	return -EINVAL;
+}
+
+static int bcm87xx_read_status(struct phy_device *phydev)
+{
+	int rx_signal_detect;
+	int pcs_status;
+	int xgxs_lane_status;
+
+	rx_signal_detect = phy_read_mmd(phydev, MDIO_MMD_PMAPMD,
+					BCM87XX_PMD_RX_SIGNAL_DETECT);
+	if (rx_signal_detect < 0)
+		return rx_signal_detect;
+
+	if ((rx_signal_detect & 1) == 0)
+		goto no_link;
+
+	pcs_status = phy_read_mmd(phydev, MDIO_MMD_PCS,
+				  BCM87XX_10GBASER_PCS_STATUS);
+	if (pcs_status < 0)
+		return pcs_status;
+
+	if ((pcs_status & 1) == 0)
+		goto no_link;
+
+	xgxs_lane_status = phy_read_mmd(phydev, MDIO_MMD_PHYXS,
+					BCM87XX_XGXS_LANE_STATUS);
+	if (xgxs_lane_status < 0)
+		return xgxs_lane_status;
+
+	if ((xgxs_lane_status & 0x1000) == 0)
+		goto no_link;
+
+	phydev->speed = 10000;
+	phydev->link = 1;
+	phydev->duplex = 1;
+	return 0;
+
+no_link:
+	phydev->link = 0;
+	return 0;
+}
+
+static int bcm87xx_config_intr(struct phy_device *phydev)
+{
+	int reg, err;
+
+	reg = phy_read_mmd(phydev, MDIO_MMD_PCS, BCM87XX_LASI_CONTROL);
+
+	if (reg < 0)
+		return reg;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = phy_read_mmd(phydev, MDIO_MMD_PCS, BCM87XX_LASI_STATUS);
+		if (err)
+			return err;
+
+		reg |= 1;
+		err = phy_write_mmd(phydev, MDIO_MMD_PCS,
+				    BCM87XX_LASI_CONTROL, reg);
+	} else {
+		reg &= ~1;
+		err = phy_write_mmd(phydev, MDIO_MMD_PCS,
+				    BCM87XX_LASI_CONTROL, reg);
+		if (err)
+			return err;
+
+		err = phy_read_mmd(phydev, MDIO_MMD_PCS, BCM87XX_LASI_STATUS);
+	}
+
+	return err;
+}
+
+static irqreturn_t bcm87xx_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	irq_status = phy_read(phydev, BCM87XX_LASI_STATUS);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (irq_status == 0)
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
+static int bcm87xx_match_phy_device(struct phy_device *phydev,
+				    const struct phy_driver *phydrv)
+{
+	return phydev->c45_ids.device_ids[4] == phydrv->phy_id;
+}
+
+static struct phy_driver bcm87xx_driver[] = {
+{
+	.phy_id		= PHY_ID_BCM8706,
+	.phy_id_mask	= 0xffffffff,
+	.name		= "Broadcom BCM8706",
+	.get_features	= bcm87xx_get_features,
+	.config_init	= bcm87xx_config_init,
+	.config_aneg	= bcm87xx_config_aneg,
+	.read_status	= bcm87xx_read_status,
+	.config_intr	= bcm87xx_config_intr,
+	.handle_interrupt = bcm87xx_handle_interrupt,
+	.match_phy_device = bcm87xx_match_phy_device,
+}, {
+	.phy_id		= PHY_ID_BCM8727,
+	.phy_id_mask	= 0xffffffff,
+	.name		= "Broadcom BCM8727",
+	.get_features	= bcm87xx_get_features,
+	.config_init	= bcm87xx_config_init,
+	.config_aneg	= bcm87xx_config_aneg,
+	.read_status	= bcm87xx_read_status,
+	.config_intr	= bcm87xx_config_intr,
+	.handle_interrupt = bcm87xx_handle_interrupt,
+	.match_phy_device = bcm87xx_match_phy_device,
+} };
+
+module_phy_driver(bcm87xx_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Broadcom BCM87xx PHY driver");