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/extcon/extcon.h | 68 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 drivers/extcon/extcon.h (limited to 'drivers/extcon/extcon.h') diff --git a/drivers/extcon/extcon.h b/drivers/extcon/extcon.h new file mode 100644 index 000000000..946182687 --- /dev/null +++ b/drivers/extcon/extcon.h @@ -0,0 +1,68 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __LINUX_EXTCON_INTERNAL_H__ +#define __LINUX_EXTCON_INTERNAL_H__ + +#include + +/** + * struct extcon_dev - An extcon device represents one external connector. + * @name: The name of this extcon device. Parent device name is + * used if NULL. + * @supported_cable: Array of supported cable names ending with EXTCON_NONE. + * If supported_cable is NULL, cable name related APIs + * are disabled. + * @mutually_exclusive: Array of mutually exclusive set of cables that cannot + * be attached simultaneously. The array should be + * ending with 0 or be NULL (no mutually exclusive cables). + * For example, if it is {0x7, 0x30, 0}, then, + * {0, 1}, {0, 1, 2}, {0, 2}, {1, 2}, or {4, 5} cannot + * be attached simulataneously. {0x7, 0} is equivalent to + * {0x3, 0x6, 0x5, 0}. If it is {0xFFFFFFFF, 0}, there + * can be no simultaneous connections. + * @dev: Device of this extcon. + * @id: Unique device ID of this extcon. + * @state: Attach/detach state of this extcon. Do not provide at + * register-time. + * @nh_all: Notifier for the state change events for all supported + * external connectors from this extcon. + * @nh: Notifier for the state change events from this extcon + * @entry: To support list of extcon devices so that users can + * search for extcon devices based on the extcon name. + * @lock: Protects device state and serialises device registration + * @max_supported: Internal value to store the number of cables. + * @extcon_dev_type: Device_type struct to provide attribute_groups + * customized for each extcon device. + * @cables: Sysfs subdirectories. Each represents one cable. + * + * In most cases, users only need to provide "User initializing data" of + * this struct when registering an extcon. In some exceptional cases, + * optional callbacks may be needed. However, the values in "internal data" + * are overwritten by register function. + */ +struct extcon_dev { + /* Optional user initializing data */ + const char *name; + const unsigned int *supported_cable; + const u32 *mutually_exclusive; + + /* Internal data. Please do not set. */ + struct device dev; + unsigned int id; + struct raw_notifier_head nh_all; + struct raw_notifier_head *nh; + struct list_head entry; + int max_supported; + spinlock_t lock; /* could be called by irq handler */ + u32 state; + + /* /sys/class/extcon/.../cable.n/... */ + struct device_type extcon_dev_type; + struct extcon_cable *cables; + + /* /sys/class/extcon/.../mutually_exclusive/... */ + struct attribute_group attr_g_muex; + struct attribute **attrs_muex; + struct device_attribute *d_attrs_muex; +}; + +#endif /* __LINUX_EXTCON_INTERNAL_H__ */ -- cgit v1.3.1