Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751605AbcDMUYE (ORCPT ); Wed, 13 Apr 2016 16:24:04 -0400 Received: from mail-qk0-f171.google.com ([209.85.220.171]:32842 "EHLO mail-qk0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750705AbcDMUYB (ORCPT ); Wed, 13 Apr 2016 16:24:01 -0400 Subject: Re: [BUG] arm64 kprobe: Allow probing at rodata To: "Wangnan (F)" , sandeepa.s.prabhu@gmail.com, wcohen@redhat.com, panand@redhat.com, Will Deacon , catalin.marinas@arm.com References: <570659E7.3040408@huawei.com> Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org From: David Long Message-ID: <570EAADD.3050805@linaro.org> Date: Wed, 13 Apr 2016 16:23:57 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <570659E7.3040408@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6098 Lines: 131 On 04/07/2016 09:00 AM, Wangnan (F) wrote: > Hi, > > When testing kprobe v12 we find a bug > > # echo 'p:kprobes/mykprobe1 ftrace_enable_fops' > > /sys/kernel/debug/tracing/kprobe_events > # echo 1 > /sys/kernel/debug/tracing/events/kprobes/mykprobe1/enable > > Unable to handle kernel paging request at virtual address d42003f0 > pgd = ffffffc009f64000 > [d42003f0] *pgd=0000000000000000, *pud=0000000000000000 > Internal error: Oops: 94000005 [#1] SMP > Modules linked in: > ... > > ftrace_enable_fops resides in rodata section, kprobe should not > allow user to put probe point on it. > > It seems arm64 intentionally puts rodata between _stext and _etext in > arch/arm64/kernel/vmlinux.lds.S, so I think we should introduce a symbol > before rodata and extra verification in kprobe on arm64. > > Thank you. > > Full output: > > # echo 'p:kprobes/mykprobe1 ftrace_enable_fops' > > /sys/kernel/debug/tracing/kprobe_events > # echo 1 > /sys/kernel/debug/tracing/events/kprobes/mykprobe1/enable > > Unable to handle kernel paging request at virtual address d42003f0 > pgd = ffffffc009f64000 > [d42003f0] *pgd=0000000000000000, *pud=0000000000000000 > Internal error: Oops: 94000005 [#1] SMP > Modules linked in: > CPU: 0 PID: 99 Comm: sh Not tainted 4.5.0+ #105 > Hardware name: linux,dummy-virt (DT) > task: ffffffc009fdc800 ti: ffffffc009ff4000 task.ti: ffffffc009ff4000 > PC is at module_put+0x38/0x218 > LR is at __fput+0xd4/0x1f4 > pc : [] lr : [] pstate: 20000145 > sp : ffffffc009ff7db0 > x29: ffffffc009ff7db0 x28: ffffffc009ff4000 > x27: ffffffc00053c000 x26: 0000000000000018 > x25: ffffffc00a01c610 x24: ffffffc0755a4f60 > x23: ffffffc075569500 x22: ffffffc0001d4c14 > x21: ffffffc0755a4f60 x20: 0000000000000008 > x19: 00000000d4200080 x18: 0000007ffdfbc7f0 > x17: 0000007fa78e3340 x16: ffffffc0001f4b84 > x15: 0000007fa796b598 x14: 000000000000024e > x13: 000000001b670000 x12: 0000000000000008 > x11: 0101010101010101 x10: ffffffc000fbdc88 > x9 : 0000000000000001 x8 : 0000000000001ffe > x7 : ffffffc009fdcfc8 x6 : 0000000000000015 > x5 : 0000000000000000 x4 : 0000000000000000 > x3 : 0000000000000001 x2 : 0000000000000000 > x1 : ffffffc009ff4000 x0 : 0000000000000001 > > Process sh (pid: 99, stack limit = 0xffffffc009ff4020) > Stack: (0xffffffc009ff7db0 to 0xffffffc009ff8000) > 7da0: ffffffc009ff7df0 ffffffc0001d4c14 > 7dc0: ffffffc00a01c600 0000000000000008 ffffffc0755a4f60 ffffffc0795f4c60 > 7de0: ffffffc075569500 ffffffc0755a4f60 ffffffc009ff7e50 ffffffc0001d4da8 > 7e00: ffffffc00a01c600 ffffffc009fdce68 ffffffc009fdc800 ffffffc0006614b0 > 7e20: ffffffc0009b3000 0000000000000015 000000000000011e 0000000000000000 > 7e40: 0000000000000058 0000000000000000 ffffffc009ff7e70 ffffffc0000ba5e0 > 7e60: 0000000000000000 ffffffc0001f4ca8 ffffffc009ff7eb0 ffffffc00008929c > 7e80: 0000000000000004 ffffffc009ff4000 ffffffffffffffff 0000007fa78e336c > 7ea0: 0000000020000000 0000000000000015 0000000000000000 ffffffc000085a9c > 7ec0: 0000000000000000 000000001b679560 0000000000000001 0000000000000001 > 7ee0: 0000000000000000 0000000000000000 000000001b67c970 0000000000000000 > 7f00: 0000000000000010 fefefefefefefefe 0000000000000018 fefefeff1a65ff30 > 7f20: 7f7f7f7f7f7f7f7f 0101010101010101 0000000000000008 000000001b670000 > 7f40: 0000000000000000 0000007fa796b598 00000000004aeb48 0000007fa78e3340 > 7f60: 0000007ffdfbc7f0 000000000000000b 000000001b679560 000000001b67c890 > 7f80: 0000000000000000 0000000000000000 0000000000000000 0000000000000002 > 7fa0: 000000001b679468 000000001b679430 000000000047edf0 0000007ffdfbca10 > 7fc0: 000000000042f770 0000007ffdfbca10 0000007fa78e336c 0000000020000000 > 7fe0: 000000000000000b 0000000000000018 0000000000000000 0000000000000000 > Call trace: > Exception stack(0xffffffc009ff7bf0 to 0xffffffc009ff7d10) > 7be0: 0000000000000000 0000000000000008 > 7c00: ffffffc009ff7db0 ffffffc000121760 ffffffc00a01c600 0000000000000015 > 7c20: ffffffc009ff7c50 ffffffc0000e7540 ffffffc0005319a8 ffffffc009fdc800 > 7c40: 0000000000000001 ffffffc0016a8000 ffffffc009ff7c90 ffffffc0000e73a4 > 7c60: ffffffc009ff7ca0 ffffffc0000e9e38 ffffffc009ff7ca0 ffffffc0000e9f70 > 7c80: 000000000000024d ffffffc009fdcf90 0000000000000001 ffffffc009ff4000 > 7ca0: 0000000000000000 0000000000000001 0000000000000000 0000000000000000 > 7cc0: 0000000000000015 ffffffc009fdcfc8 0000000000001ffe 0000000000000001 > 7ce0: ffffffc000fbdc88 0101010101010101 0000000000000008 000000001b670000 > 7d00: 000000000000024e 0000007fa796b598 > [] module_put+0x38/0x218 > [] __fput+0xd4/0x1f4 > [] ____fput+0x20/0x2c > [] task_work_run+0xb8/0xec > [] do_notify_resume+0x5c/0x70 > [] work_pending+0x10/0x14 > Code: d5384101 b9401820 11000400 b9001820 (b9437263) > ---[ end trace adc71e553dfc48ff ]--- > note: sh[99] exited with preempt_count 1 > Thanks for the bug report. Symbols already exist bracketing rodata. I have made the following change and it seems to achieve the desired affect. Unless I hear objections I will add this to the v12 changes when I post them (soon): diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c index 13d3333..6b6ec28 100644 --- a/arch/arm64/kernel/kprobes.c +++ b/arch/arm64/kernel/kprobes.c @@ -81,12 +81,17 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) int __kprobes arch_prepare_kprobe(struct kprobe *p) { unsigned long probe_addr = (unsigned long)p->addr; + extern char __start_rodata[]; + extern char __end_rodata[]; /* copy instruction */ p->opcode = le32_to_cpu(*p->addr); if (in_exception_text(probe_addr)) return -EINVAL; + if (probe_addr >= (unsigned long) __start_rodata && + probe_addr <= (unsigned long) __end_rodata) + return -EINVAL; /* decode instruction */ switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {