Messages in this thread | | | Date | Mon, 1 Aug 2022 11:44:45 +0800 | Subject | Re: [PATCH] kprobes: Forbid probing on kprobe_insn_slot | From | Chen Zhongjin <> |
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Hi,
On 2022/7/31 23:48, Masami Hiramatsu (Google) wrote: > On Wed, 27 Jul 2022 11:20:58 +0800 > Chen Zhongjin <chenzhongjin@huawei.com> wrote: > >> Syzkaller reported a BUG on arm64: >> Unrecoverable kprobe detected. >> Dumping kprobe: >> Name: (null) >> Offset: 0 >> Address: 0xffffa00010019000 >> ------------[ cut here ]------------ >> kernel BUG at arch/arm64/kernel/probes/kprobes.c:235! >> Internal error: Oops - BUG: 0 [#1] SMP >> Modules linked in: >> CPU: 1 PID: 31060 Comm: syz-executor.6 Not tainted 5.10.0 #11 >> ... >> Call trace: >> reenter_kprobe arch/arm64/kernel/probes/kprobes.c:234 [inline] >> kprobe_handler+0x23c/0x26c arch/arm64/kernel/probes/kprobes.c:339 >> kprobe_breakpoint_handler+0x24/0x34 arch/arm64/kernel/probes/kprobes.c:406 >> call_break_hook+0xf4/0x13c arch/arm64/kernel/debug-monitors.c:322 >> brk_handler+0x2c/0xa0 arch/arm64/kernel/debug-monitors.c:329 >> do_debug_exception+0x140/0x230 arch/arm64/mm/fault.c:867 >> el1_dbg+0x38/0x50 arch/arm64/kernel/entry-common.c:182 >> el1_sync_handler+0xf4/0x150 arch/arm64/kernel/entry-common.c:219 >> el1_sync+0x74/0x100 arch/arm64/kernel/entry.S:665 >> 0xffffa00010019000 >> do_futex+0x2f4/0x370 kernel/futex.c:3735 >> __do_sys_futex kernel/futex.c:3798 [inline] >> __se_sys_futex kernel/futex.c:3764 [inline] >> __arm64_sys_futex+0x168/0x3a0 kernel/futex.c:3764 >> __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline] >> invoke_syscall arch/arm64/kernel/syscall.c:48 [inline] >> el0_svc_common.constprop.0+0xf4/0x414 arch/arm64/kernel/syscall.c:155 >> do_el0_svc+0x50/0x11c arch/arm64/kernel/syscall.c:217 >> el0_svc+0x20/0x30 arch/arm64/kernel/entry-common.c:353 >> el0_sync_handler+0xe4/0x1e0 arch/arm64/kernel/entry-common.c:369 >> el0_sync+0x148/0x180 arch/arm64/kernel/entry.S:683 >> Code: 91018360 97ff1838 aa1703e0 97ff1fdf (d4210000) >> ---[ end trace 767503e946e01b15 ]--- >> >> Syzbot tried to porbe on a kprobe_insn_slot. >> >> kprobe will replace instruciton with a break and store the origin one >> on kprobe_insn_slot. However these slots are not in .kprobes.text and >> exported by perf_event_ksymbol so can be probed by perf interface. >> >> Probing these slots will triggers kprobe handler inside single step >> process and for some architectures such as arm64 this will causes a >> bug(). >> >> These slots are kprobe process so they should not be probed anyway. >> Add kprobe_insn_slot check when register_kprobe to forbid probing on >> these slots. > Oops, good catch! > > Previously this was not counted as text area, but now the kernel_text_address() > returns true for these trampoline buffers. > > In this case, I think kprobes should be limited to probe only > core_kernel_text and module_text. > Can you use is_module_text_address() and core_kernel_text() instead? > Below can allow kprobes probing on other trampolines like ftrace and > bpf. > Also, you may need this tag; > > Fixes: 5b485629ba0d ("kprobes, extable: Identify kprobes trampolines as kernel text area") > > Thank you,
Thanks for review!
Please see next version here: https://lkml.org/lkml/2022/7/31/436
[PATCH v3] kprobes: Forbid probing on trampoline and bpf prog
>> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com> >> --- >> kernel/kprobes.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/kernel/kprobes.c b/kernel/kprobes.c >> index f214f8c088ed..3e798b62db70 100644 >> --- a/kernel/kprobes.c >> +++ b/kernel/kprobes.c >> @@ -1562,6 +1562,8 @@ static int check_kprobe_address_safe(struct kprobe *p, >> /* Ensure it is not in reserved area nor out of text */ >> if (!kernel_text_address((unsigned long) p->addr) || >> within_kprobe_blacklist((unsigned long) p->addr) || >> + is_kprobe_insn_slot((unsigned long) p->addr) || >> + is_kprobe_optinsn_slot((unsigned long) p->addr) || >> jump_label_text_reserved(p->addr, p->addr) || >> static_call_text_reserved(p->addr, p->addr) || >> find_bug((unsigned long)p->addr)) { >> -- >> 2.17.1 >> Best,
Chen
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