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 --- include/uapi/asm-generic/signal.h | 93 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 include/uapi/asm-generic/signal.h (limited to 'include/uapi/asm-generic/signal.h') diff --git a/include/uapi/asm-generic/signal.h b/include/uapi/asm-generic/signal.h new file mode 100644 index 000000000..0eb69dc8e --- /dev/null +++ b/include/uapi/asm-generic/signal.h @@ -0,0 +1,93 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI__ASM_GENERIC_SIGNAL_H +#define _UAPI__ASM_GENERIC_SIGNAL_H + +#include + +#define _NSIG 64 +#define _NSIG_BPW __BITS_PER_LONG +#define _NSIG_WORDS (_NSIG / _NSIG_BPW) + +#define SIGHUP 1 +#define SIGINT 2 +#define SIGQUIT 3 +#define SIGILL 4 +#define SIGTRAP 5 +#define SIGABRT 6 +#define SIGIOT 6 +#define SIGBUS 7 +#define SIGFPE 8 +#define SIGKILL 9 +#define SIGUSR1 10 +#define SIGSEGV 11 +#define SIGUSR2 12 +#define SIGPIPE 13 +#define SIGALRM 14 +#define SIGTERM 15 +#define SIGSTKFLT 16 +#define SIGCHLD 17 +#define SIGCONT 18 +#define SIGSTOP 19 +#define SIGTSTP 20 +#define SIGTTIN 21 +#define SIGTTOU 22 +#define SIGURG 23 +#define SIGXCPU 24 +#define SIGXFSZ 25 +#define SIGVTALRM 26 +#define SIGPROF 27 +#define SIGWINCH 28 +#define SIGIO 29 +#define SIGPOLL SIGIO +/* +#define SIGLOST 29 +*/ +#define SIGPWR 30 +#define SIGSYS 31 +#define SIGUNUSED 31 + +/* These should not be considered constants from userland. */ +#define SIGRTMIN 32 +#ifndef SIGRTMAX +#define SIGRTMAX _NSIG +#endif + +#if !defined MINSIGSTKSZ || !defined SIGSTKSZ +#define MINSIGSTKSZ 2048 +#define SIGSTKSZ 8192 +#endif + +#ifndef __ASSEMBLY__ +typedef struct { + unsigned long sig[_NSIG_WORDS]; +} sigset_t; + +/* not actually used, but required for linux/syscalls.h */ +typedef unsigned long old_sigset_t; + +#include + +#ifdef SA_RESTORER +#define __ARCH_HAS_SA_RESTORER +#endif + +#ifndef __KERNEL__ +struct sigaction { + __sighandler_t sa_handler; + unsigned long sa_flags; +#ifdef SA_RESTORER + __sigrestore_t sa_restorer; +#endif + sigset_t sa_mask; /* mask last for extensibility */ +}; +#endif + +typedef struct sigaltstack { + void __user *ss_sp; + int ss_flags; + __kernel_size_t ss_size; +} stack_t; + +#endif /* __ASSEMBLY__ */ + +#endif /* _UAPI__ASM_GENERIC_SIGNAL_H */ -- cgit v1.3.1