From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/net/phy/amd.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 drivers/net/phy/amd.c (limited to 'drivers/net/phy/amd.c') diff --git a/drivers/net/phy/amd.c b/drivers/net/phy/amd.c new file mode 100644 index 000000000..75b5fe655 --- /dev/null +++ b/drivers/net/phy/amd.c @@ -0,0 +1,120 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Driver for AMD am79c PHYs + * + * Author: Heiko Schocher + * + * Copyright (c) 2011 DENX Software Engineering GmbH + */ +#include +#include +#include +#include +#include +#include + +#define PHY_ID_AC101L 0x00225520 +#define PHY_ID_AM79C874 0x0022561b + +#define MII_AM79C_IR 17 /* Interrupt Status/Control Register */ +#define MII_AM79C_IR_EN_LINK 0x0400 /* IR enable Linkstate */ +#define MII_AM79C_IR_EN_ANEG 0x0100 /* IR enable Aneg Complete */ +#define MII_AM79C_IR_IMASK_INIT (MII_AM79C_IR_EN_LINK | MII_AM79C_IR_EN_ANEG) + +#define MII_AM79C_IR_LINK_DOWN BIT(2) +#define MII_AM79C_IR_ANEG_DONE BIT(0) +#define MII_AM79C_IR_IMASK_STAT (MII_AM79C_IR_LINK_DOWN | MII_AM79C_IR_ANEG_DONE) + +MODULE_DESCRIPTION("AMD PHY driver"); +MODULE_AUTHOR("Heiko Schocher "); +MODULE_LICENSE("GPL"); + +static int am79c_ack_interrupt(struct phy_device *phydev) +{ + int err; + + err = phy_read(phydev, MII_BMSR); + if (err < 0) + return err; + + err = phy_read(phydev, MII_AM79C_IR); + if (err < 0) + return err; + + return 0; +} + +static int am79c_config_init(struct phy_device *phydev) +{ + return 0; +} + +static int am79c_config_intr(struct phy_device *phydev) +{ + int err; + + if (phydev->interrupts == PHY_INTERRUPT_ENABLED) { + err = am79c_ack_interrupt(phydev); + if (err) + return err; + + err = phy_write(phydev, MII_AM79C_IR, MII_AM79C_IR_IMASK_INIT); + } else { + err = phy_write(phydev, MII_AM79C_IR, 0); + if (err) + return err; + + err = am79c_ack_interrupt(phydev); + } + + return err; +} + +static irqreturn_t am79c_handle_interrupt(struct phy_device *phydev) +{ + int irq_status; + + irq_status = phy_read(phydev, MII_AM79C_IR); + if (irq_status < 0) { + phy_error(phydev); + return IRQ_NONE; + } + + if (!(irq_status & MII_AM79C_IR_IMASK_STAT)) + return IRQ_NONE; + + phy_trigger_machine(phydev); + + return IRQ_HANDLED; +} + +static struct phy_driver am79c_drivers[] = { + { + .phy_id = PHY_ID_AM79C874, + .name = "AM79C874", + .phy_id_mask = 0xfffffff0, + /* PHY_BASIC_FEATURES */ + .config_init = am79c_config_init, + .config_intr = am79c_config_intr, + .handle_interrupt = am79c_handle_interrupt, + }, + { + .phy_id = PHY_ID_AC101L, + .name = "AC101L", + .phy_id_mask = 0xfffffff0, + /* PHY_BASIC_FEATURES */ + .config_init = am79c_config_init, + .config_intr = am79c_config_intr, + .handle_interrupt = am79c_handle_interrupt, + }, +}; + +module_phy_driver(am79c_drivers); + +static const struct mdio_device_id __maybe_unused amd_tbl[] = { + { PHY_ID_AC101L, 0xfffffff0 }, + { PHY_ID_AM79C874, 0xfffffff0 }, + { } +}; + +MODULE_DEVICE_TABLE(mdio, amd_tbl); -- cgit v1.3.1