From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7102C10F03 for ; Fri, 1 Mar 2019 23:00:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD28320848 for ; Fri, 1 Mar 2019 23:00:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726337AbfCAXAZ (ORCPT ); Fri, 1 Mar 2019 18:00:25 -0500 Received: from mail-qk1-f193.google.com ([209.85.222.193]:46048 "EHLO mail-qk1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726693AbfCAXAY (ORCPT ); Fri, 1 Mar 2019 18:00:24 -0500 Received: by mail-qk1-f193.google.com with SMTP id v139so15306713qkb.12 for ; Fri, 01 Mar 2019 15:00:23 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=NCIX/43FE8u7QVkPRu8lMcjtW87sMpYmpGvTDgosx1g=; b=C0OfgdCt7VH+oLDR6nAmb5SxHAYMGfK2g1lgC9H2wjKEhF1/HP8fIfLL8TQ0gkGigl 1MLuqIxsbYXsOpcciUcq5e2+UlEh9HY2Jd5jaEga5rjcRIFx7gEV69Vi101kSgQ2rU/o q7dr4scF/BNLkAfQ9WEqlOYtQ4gctKPQ8AadUE0fiFqlvLv1ljVd/Zqgp6Szvj4+yo8h CQ6gdCdI9kdzcriEITsuxoD0h/h2t/1MjPB4pBWbv8KHaB7asxBzg3YLO9PTnNYoCyud RfgSYH+E8pkO75ZtFGBzKBZllIWleYCh8LAapXl28jdrtk7r5ZqK0PtGKdvC/qR0epLe itMA== X-Gm-Message-State: APjAAAVdyAAZOYi97UCf4wUJMJvBJBsmn7xv4SI6kp7wq2xoz/c+0C1+ zmYPa+rI1/tr3kvdsHWbjQK9WrGFamXBKg== X-Google-Smtp-Source: APXvYqwUBDbutsz/7xBk6ONr2/RbZxUK/QesF+fQH5xMvb+3BOcq6aw3eZ5PaHk76C05DglV6qtixg== X-Received: by 2002:a37:4b49:: with SMTP id y70mr5727861qka.134.1551481223084; Fri, 01 Mar 2019 15:00:23 -0800 (PST) Received: from localhost.localdomain (h69-128-230-203.cntcnh.dsl.dynamic.tds.net. [69.128.230.203]) by smtp.gmail.com with ESMTPSA id n66sm9061255qkl.38.2019.03.01.15.00.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 01 Mar 2019 15:00:22 -0800 (PST) Subject: Re: [RFC] kprobes: Fix locking in recycle_rp_inst To: Masami Hiramatsu , Jiri Olsa , Ingo Molnar Cc: Jiri Olsa , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , lkml , Srinivasa D S , Hien Nguyen , stable@vger.kernel.org References: <20190226161036.10680-1-jolsa@kernel.org> <20190227173846.397e2a66da37e0385d3fc383@kernel.org> <20190227133309.GL18893@krava> <20190228155032.87b2a87926318744b64eee89@kernel.org> From: David Valin Message-ID: <7f02944d-b859-4716-c786-d0dee6feab20@redhat.com> Date: Fri, 1 Mar 2019 18:00:20 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190228155032.87b2a87926318744b64eee89@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Finally got around to testing it.  Verified the issue was still present.  Then install Jiri's fix.  Cleared the issue out.  So at least from the standpoint of fixing the hang, the change is good. Dave On 2/28/19 1:50 AM, Masami Hiramatsu wrote: > On Wed, 27 Feb 2019 14:33:09 +0100 > Jiri Olsa wrote: > >> On Wed, Feb 27, 2019 at 05:38:46PM +0900, Masami Hiramatsu wrote: >> >> SNIP >> >>>> When we switch it to raw_spin_lock_irqsave the return probe >>>> on _raw_spin_lock starts working. >>> Yes, there can be a race between probes and probe on irq handler. >>> >>> kretprobe_hash_lock()/kretprobe_hash_unlock() are safe because >>> those disables irqs. Only recycle_rp_inst() has this problem. >>> >>> Acked-by: Masami Hiramatsu >>> >>> And this is one of the oldest bug in kprobe. >>> >>> commit ef53d9c5e4da ("kprobes: improve kretprobe scalability with hashed locking") >>> >>> introduced the spin_lock(&rp->lock) in recycle_rp_inst() but forgot to disable irqs. >>> And >>> >>> commit c9becf58d935 ("[PATCH] kretprobe: kretprobe-booster") >> ok, so I'll add: >> >> Fixes: c9becf58d935 ("[PATCH] kretprobe: kretprobe-booster") >> >>> introduced assembly-based trampoline which didn't disable irq. >>> >>> Could you add Cc:stable to this patch too? >> sure, attaching patch with updated changelog > Thank you Jiri, > > Ingo, could you pick this patch? (and my kretprobe fixup series?) > > Thank you, > >> thanks, >> jirka >> >> >> --- >> We can call recycle_rp_inst from both task and irq contexts, >> so we should irqsave/irqrestore locking functions. >> >> I wasn't able to hit this particular lockup, but I found it >> while checking on why return probe on _raw_spin_lock locks >> the system, reported by David by using bpftrace on simple >> script, like: >> >> kprobe:_raw_spin_lock >> { >> @time[tid] = nsecs; >> @symb[tid] = arg0; >> } >> >> kretprobe:_raw_spin_lock >> / @time[tid] / >> { >> delete(@time[tid]); >> delete(@symb[tid]); >> } >> >> or by perf tool: >> >> # perf probe -a _raw_spin_lock:%return >> # perf record -e probe:_raw_spin_lock__return -a >> >> The thing is that the _raw_spin_lock call in recycle_rp_inst, >> is the only one that return probe code paths call and it will >> trigger another kprobe instance while already processing one >> and lock up on kretprobe_table_lock lock: >> >> #12 [ffff99c337403d28] queued_spin_lock_slowpath at ffffffff9712693b >> #13 [ffff99c337403d28] _raw_spin_lock_irqsave at ffffffff9794c100 >> #14 [ffff99c337403d38] pre_handler_kretprobe at ffffffff9719435c >> #15 [ffff99c337403d68] kprobe_ftrace_handler at ffffffff97059f12 >> #16 [ffff99c337403d98] ftrace_ops_assist_func at ffffffff971a0421 >> #17 [ffff99c337403dd8] handle_edge_irq at ffffffff97139f55 >> #18 [ffff99c337403df0] handle_edge_irq at ffffffff97139f55 >> #19 [ffff99c337403e58] _raw_spin_lock at ffffffff9794c111 >> #20 [ffff99c337403e88] _raw_spin_lock at ffffffff9794c115 >> #21 [ffff99c337403ea8] trampoline_handler at ffffffff97058a8f >> #22 [ffff99c337403f00] kretprobe_trampoline at ffffffff970586d5 >> #23 [ffff99c337403fb0] handle_irq at ffffffff97027b1f >> #24 [ffff99c337403fc0] do_IRQ at ffffffff97a01bc9 >> --- --- >> #25 [ffffa5c3c1f9fb38] ret_from_intr at ffffffff97a0098f >> [exception RIP: smp_call_function_many+460] >> RIP: ffffffff9716685c RSP: ffffa5c3c1f9fbe0 RFLAGS: 00000202 >> RAX: 0000000000000005 RBX: ffff99c337421c80 RCX: ffff99c337566260 >> RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff99c337421c88 >> RBP: ffff99c337421c88 R8: 0000000000000001 R9: ffffffff98352940 >> R10: ffff99c33703c910 R11: ffffffff9794c110 R12: ffffffff97055680 >> R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000040 >> ORIG_RAX: ffffffffffffffde CS: 0010 SS: 0018 >> #26 [ffffa5c3c1f9fc20] on_each_cpu at ffffffff97166918 >> #27 [ffffa5c3c1f9fc40] ftrace_replace_code at ffffffff97055a34 >> #28 [ffffa5c3c1f9fc88] ftrace_modify_all_code at ffffffff971a3552 >> #29 [ffffa5c3c1f9fca8] arch_ftrace_update_code at ffffffff97055a6c >> #30 [ffffa5c3c1f9fcb0] ftrace_run_update_code at ffffffff971a3683 >> #31 [ffffa5c3c1f9fcc0] ftrace_startup at ffffffff971a6638 >> #32 [ffffa5c3c1f9fce8] register_ftrace_function at ffffffff971a66a0 >> >> When we switch it to raw_spin_lock_irqsave the return probe >> on _raw_spin_lock starts working. >> >> Fixes: c9becf58d935 ("[PATCH] kretprobe: kretprobe-booster") >> Cc: stable@vger.kernel.org >> Reported-by: David Valin >> Acked-by: Masami Hiramatsu >> Signed-off-by: Jiri Olsa >> --- >> kernel/kprobes.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/kprobes.c b/kernel/kprobes.c >> index c83e54727131..c82056b354cc 100644 >> --- a/kernel/kprobes.c >> +++ b/kernel/kprobes.c >> @@ -1154,9 +1154,11 @@ void recycle_rp_inst(struct kretprobe_instance *ri, >> hlist_del(&ri->hlist); >> INIT_HLIST_NODE(&ri->hlist); >> if (likely(rp)) { >> - raw_spin_lock(&rp->lock); >> + unsigned long flags; >> + >> + raw_spin_lock_irqsave(&rp->lock, flags); >> hlist_add_head(&ri->hlist, &rp->free_instances); >> - raw_spin_unlock(&rp->lock); >> + raw_spin_unlock_irqrestore(&rp->lock, flags); >> } else >> /* Unregistering */ >> hlist_add_head(&ri->hlist, head); >> -- >> 2.17.2 >> >