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 --- lib/xz/Kconfig | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 lib/xz/Kconfig (limited to 'lib/xz/Kconfig') diff --git a/lib/xz/Kconfig b/lib/xz/Kconfig new file mode 100644 index 000000000..20aa459bf --- /dev/null +++ b/lib/xz/Kconfig @@ -0,0 +1,77 @@ +# SPDX-License-Identifier: GPL-2.0-only +config XZ_DEC + tristate "XZ decompression support" + select CRC32 + help + LZMA2 compression algorithm and BCJ filters are supported using + the .xz file format as the container. For integrity checking, + CRC32 is supported. See Documentation/staging/xz.rst for more + information. + +if XZ_DEC + +config XZ_DEC_X86 + bool "x86 BCJ filter decoder" if EXPERT + default y + select XZ_DEC_BCJ + +config XZ_DEC_POWERPC + bool "PowerPC BCJ filter decoder" if EXPERT + default y + select XZ_DEC_BCJ + +config XZ_DEC_ARM + bool "ARM BCJ filter decoder" if EXPERT + default y + select XZ_DEC_BCJ + +config XZ_DEC_ARMTHUMB + bool "ARM-Thumb BCJ filter decoder" if EXPERT + default y + select XZ_DEC_BCJ + +config XZ_DEC_ARM64 + bool "ARM64 BCJ filter decoder" if EXPERT + default y + select XZ_DEC_BCJ + +config XZ_DEC_SPARC + bool "SPARC BCJ filter decoder" if EXPERT + default y + select XZ_DEC_BCJ + +config XZ_DEC_RISCV + bool "RISC-V BCJ filter decoder" if EXPERT + default y + select XZ_DEC_BCJ + +config XZ_DEC_MICROLZMA + bool "MicroLZMA decoder" + default n + help + MicroLZMA is a header format variant where the first byte + of a raw LZMA stream (without the end of stream marker) has + been replaced with a bitwise-negation of the lc/lp/pb + properties byte. MicroLZMA was created to be used in EROFS + but can be used by other things too where wasting minimal + amount of space for headers is important. + + Unless you know that you need this, say N. + +endif + +config XZ_DEC_BCJ + bool + default n + +config XZ_DEC_TEST + tristate "XZ decompressor tester" + default n + depends on XZ_DEC + help + This allows passing .xz files to the in-kernel XZ decoder via + a character special file. It calculates CRC32 of the decompressed + data and writes diagnostics to the system log. + + Unless you are developing the XZ decoder, you don't need this + and should say N. -- cgit v1.3.1