From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751996AbaCUVj2 (ORCPT ); Fri, 21 Mar 2014 17:39:28 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:47939 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750759AbaCUVjZ (ORCPT ); Fri, 21 Mar 2014 17:39:25 -0400 Date: Fri, 21 Mar 2014 17:39:22 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andi Kleen , Ananth N Mavinakayanahalli , Sandeepa Prabhu , Frederic Weisbecker , x86@kernel.org, fche@redhat.com, mingo@redhat.com, systemtap@sourceware.org, "H. Peter Anvin" , Thomas Gleixner Subject: Re: [PATCH -tip v8 01/26] [BUGFIX]kprobes/x86: Fix page-fault handling logic Message-ID: <20140321173922.76348fdd@gandalf.local.home> In-Reply-To: <20140305115850.22766.13456.stgit@ltc230.yrl.intra.hitachi.co.jp> References: <20140305115843.22766.8355.stgit@ltc230.yrl.intra.hitachi.co.jp> <20140305115850.22766.13456.stgit@ltc230.yrl.intra.hitachi.co.jp> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 05 Mar 2014 20:58:50 +0900 Masami Hiramatsu wrote: > Current kprobes in-kernel page fault handler doesn't > expect that its single-stepping can be interrupted by > an NMI handler which may cause a page fault(e.g. perf > with callback tracing). > In that case, the page-fault handled by kprobes and it > misunderstands the page-fault has been caused by the > single-stepping code and tries to recover IP address > to probed address. > But the truth is the page-fault has been caused by the > NMI handler, and do_page_fault failes to handle real > page fault because the IP address is modified and > causes Kernel BUGs like below. > > ---- > [ 2264.726905] BUG: unable to handle kernel NULL pointer > dereference at 0000000000000020 > [ 2264.727190] IP: [] copy_user_generic_string+0x0/0x40 > [ 2264.727380] PGD cbcd067 PUD cbcc067 PMD 0 > [ 2264.727529] Oops: 0000 [#1] SMP > [ 2264.727683] Modules linked in: ipt_MASQUERADE bnep bluetooth 6lowpan_iphc iptable_nat nf_nat_ipv4 nf_nat aesni_intel aes_x86_64 ablk_helper cryptd lrw gf128mul glue_helper virtio_balloon snd_hda_intel snd_hda_codec snd_hwdep > [ 2264.728391] CPU: 1 PID: 25094 Comm: perf Not tainted 3.14.0-rc1.badprobe+ #24 > [ 2264.728592] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 2264.728747] task: ffff88003db9c210 ti: ffff88000caac000 task.ti: ffff88000caac000 > [ 2264.728950] RIP: 0010:[] [] copy_user_generic_string+0x0/0x40 > [ 2264.729163] RSP: 0018:ffff88003fd06bd0 EFLAGS: 00010246 > [ 2264.729291] RAX: 0000000000000000 RBX: ffff88003fd06bf8 RCX: 0000000000000002 > [ 2264.729472] RDX: 0000000000000000 RSI: 0000000000000020 RDI: ffff88003fd06bf8 > [ 2264.729661] RBP: ffff88003fd06bd8 R08: 0000000000000030 R09: 0000000000000000 > [ 2264.729789] R10: 000000000000001e R11: 0000000000000015 R12: ffff88000caadfd8 > [ 2264.729789] R13: ffff88003d76bc00 R14: ffff88003db9c210 R15: 0000000000000020 > [ 2264.729789] FS: 00007f398bbcc780(0000) GS:ffff88003fd00000(0000) knlGS:0000000000000000 > [ 2264.729789] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 2264.729789] CR2: 0000000000000020 CR3: 00000000204f2000 CR4: 00000000000007e0 > [ 2264.729789] Stack: > [ 2264.729789] ffffffff813c5fd4 ffff88003fd06c30 ffffffff810183b0 ffff88003d76bc00 > [ 2264.729789] ffff88003fd06ef8 0000000000000000 0000000000000000 ffff88003d76bc00 > [ 2264.729789] 000000000000000c 0000000000052ce0 ffff88000956f800 ffff88000caadf58 > [ 2264.729789] Call Trace: > [ 2264.729789] > [ 2264.729789] [] ? copy_from_user_nmi+0x64/0x70 > [ 2264.729789] [] perf_callchain_user+0xc0/0x220 > [ 2264.729789] [] perf_callchain+0x1c4/0x210 > [ 2264.729789] [] perf_prepare_sample+0x253/0x320 > [ 2264.729789] [] __perf_event_overflow+0xe7/0x230 > [ 2264.729789] [] ? x86_perf_event_set_period+0xe8/0x150 > [ 2264.729789] [] perf_event_overflow+0x14/0x20 > [ 2264.729789] [] intel_pmu_handle_irq+0x1cd/0x400 > [ 2264.729789] [] ? ftrace_regs_caller+0x81/0xcd > [ 2264.729789] [] ? copy_user_generic_unrolled+0xc0/0xc0 > [ 2264.729789] [] perf_event_nmi_handler+0x2b/0x50 > [ 2264.729789] [] nmi_handle+0x88/0x180 > [ 2264.729789] [] ? copy_user_generic_unrolled+0xc0/0xc0 > [ 2264.729789] [] default_do_nmi+0x4a/0x140 > [ 2264.729789] [] do_nmi+0xa8/0xe0 > [ 2264.729789] [] end_repeat_nmi+0x1e/0x2e > [ 2264.729789] [] ? copy_user_generic_unrolled+0xc0/0xc0 > [ 2264.729789] [] ? skip_prefixes+0x1c/0x40 > [ 2264.729789] [] ? bad_get_user+0x17/0x17 > [ 2264.729789] [] ? ftrace_regs_caller+0x81/0xcd > [ 2264.729789] [] ? ftrace_regs_caller+0x81/0xcd > [ 2264.729789] [] ? ftrace_regs_caller+0x81/0xcd > [ 2264.729789] <> > [ 2264.729789] <#DB> [] ? copy_user_generic_unrolled+0xc0/0xc0 > [ 2264.729789] [] ? copy_user_generic_string+0x1/0x40 > [ 2264.729789] [] ? ftrace_cmp_recs+0x1/0x30 > [ 2264.729789] [] ? inat_get_opcode_attribute+0x5/0x20 > [ 2264.729789] [] ? inat_get_opcode_attribute+0x5/0x20 > [ 2264.729789] [] ? skip_prefixes+0x1c/0x40 > [ 2264.729789] [] resume_execution+0x37/0x1d0 > [ 2264.729789] [] kprobe_debug_handler+0x3f/0xe0 > [ 2264.729789] [] do_debug+0x7f/0x1d0 > [ 2264.729789] [] debug+0x3a/0x50 > [ 2264.729789] <> > [ 2264.729789] [] ? seq_read+0x88/0x390 > [ 2264.729789] [] ? security_file_permission+0x84/0xa0 > [ 2264.729789] [] proc_reg_read+0x3d/0x80 > [ 2264.729789] [] vfs_read+0x9b/0x160 > [ 2264.729789] [] SyS_read+0x49/0xa0 > [ 2264.729789] [] system_call_fastpath+0x16/0x1b > [ 2264.729789] Code: c9 75 ee 21 d2 74 10 89 d1 8a 06 88 07 48 ff c6 48 ff c7 ff > c9 75 f2 31 c0 0f 1f 00 c3 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 1f 00 > 83 fa 08 72 27 89 f9 83 e1 07 74 15 83 e9 08 f7 d9 29 > [ 2264.729789] RIP [] copy_user_generic_string+0x0/0x40 > [ 2264.729789] RSP > [ 2264.729789] CR2: 0000000000000020 > [ 2264.729789] ---[ end trace 533fc16b4cc45447 ]--- > [ 2264.729789] Kernel panic - not syncing: Fatal exception in interrupt > [ 2264.729789] Kernel Offset: 0x0 from 0xffffffff81000000 (relocation range: 0xf > fffffff80000000-0xffffffff9fffffff) > ---- > > To handle this correctly, I fixed the kprobes fault > handler to ensure the faulted ip address is its own > single-step buffer instead of checking current kprobe > state. > > > Signed-off-by: Masami Hiramatsu > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > --- > arch/x86/kernel/kprobes/core.c | 13 ++++--------- > 1 file changed, 4 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > index 79a3f96..b482e96 100644 > --- a/arch/x86/kernel/kprobes/core.c > +++ b/arch/x86/kernel/kprobes/core.c > @@ -897,9 +897,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) > struct kprobe *cur = kprobe_running(); > struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); > > - switch (kcb->kprobe_status) { > - case KPROBE_HIT_SS: > - case KPROBE_REENTER: > + if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) { I wonder if we should add a: WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS && kcb->kprobe_status != KPROBE_REENTER); -- Steve > /* > * We are here because the instruction being single > * stepped caused a page fault. We reset the current > @@ -914,9 +912,8 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) > else > reset_current_kprobe(); > preempt_enable_no_resched(); > - break; > - case KPROBE_HIT_ACTIVE: > - case KPROBE_HIT_SSDONE: > + } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE || > + kcb->kprobe_status == KPROBE_HIT_SSDONE) { > /* > * We increment the nmissed count for accounting, > * we can also use npre/npostfault count for accounting > @@ -945,10 +942,8 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) > * fixup routine could not handle it, > * Let do_page_fault() fix it. > */ > - break; > - default: > - break; > } > + > return 0; > } > >