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 --- scripts/misc-check | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100755 scripts/misc-check (limited to 'scripts/misc-check') diff --git a/scripts/misc-check b/scripts/misc-check new file mode 100755 index 000000000..40e5a4b01 --- /dev/null +++ b/scripts/misc-check @@ -0,0 +1,76 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0-only + +set -e + +# Detect files that are tracked but ignored by git. +check_tracked_ignored_files () { + git -C "${srctree:-.}" ls-files -i -c --exclude-per-directory=.gitignore 2>/dev/null | + sed 's/$/: warning: ignored by one of the .gitignore files/' >&2 +} + +# Check for missing #include +# +# The rule for including is very simple: +# Include only when you use EXPORT_SYMBOL(). That's it. +# +# However, some headers include even though they are completely +# unrelated to EXPORT_SYMBOL(). +# +# One example is include/linux/module.h. Please note and +# are orthogonal. should be included by files +# that can be compiled as modules. In other words, should be +# included by EXPORT_SYMBOL consumers. In contrast, should be +# included from EXPORT_SYMBOL providers, which may or may not be modular. +# Hence, include/linux/module.h should *not* include . +# +# Another example is include/linux/linkage.h, which is completely unrelated to +# EXPORT_SYMBOL(). Worse, it is included by most C files, which means, most C +# files end up including , even though only some of them +# actually export symbols. Hence, include/linux/linkage.h should *not* include +# . +# +# Before fixing such headers, we must ensure that C files using EXPORT_SYMBOL() +# include directly, since many C files currently rely on +# being included indirectly (likely, via etc.). +# +# Therefore, this check. +# +# The problem is simple - the warned files use EXPORT_SYMBOL(), but do not +# include . Please add #include to them. +# +# If the included headers are sorted alphabetically, please insert +# in the appropriate position to maintain the sort order. +# For this reason, this script only checks missing , but +# does not automatically fix it. +check_missing_include_linux_export_h () { + + git -C "${srctree:-.}" grep --files-with-matches -E 'EXPORT_SYMBOL((_NS)?(_GPL)?|_FOR_MODULES)\(.*\)' \ + -- '*.[ch]' :^tools/ :^include/linux/export.h | + xargs -r git -C "${srctree:-.}" grep --files-without-match '#include[[:space:]]*' | + xargs -r printf "%s: warning: EXPORT_SYMBOL() is used, but #include is missing\n" >&2 +} + +# If you do not use EXPORT_SYMBOL(), please do not include . +# Currently, this is checked for *.c files, but not for *.h files, because some +# *.c files rely on being included indirectly. +check_unnecessary_include_linux_export_h () { + + git -C "${srctree:-.}" grep --files-with-matches '#include[[:space:]]*' \ + -- '*.[c]' :^tools/ | + xargs -r git -C "${srctree:-.}" grep --files-without-match -E 'EXPORT_SYMBOL((_NS)?(_GPL)?|_FOR_MODULES)\(.*\)' | + xargs -r printf "%s: warning: EXPORT_SYMBOL() is not used, but #include is present\n" >&2 +} + +case "${KBUILD_EXTRA_WARN}" in +*1*) + check_tracked_ignored_files + ;; +esac + +case "${KBUILD_EXTRA_WARN}" in +*2*) + check_missing_include_linux_export_h + check_unnecessary_include_linux_export_h + ;; +esac -- cgit v1.3.1