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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 8F100C2BA83 for ; Sat, 15 Feb 2020 10:30:20 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 38A782086A for ; Sat, 15 Feb 2020 10:30:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="BnhPxxwg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 38A782086A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48KRMs6TqwzDqlD for ; Sat, 15 Feb 2020 21:30:17 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=c-s.fr (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@c-s.fr; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=c-s.fr header.i=@c-s.fr header.a=rsa-sha256 header.s=mail header.b=BnhPxxwg; dkim-atps=neutral Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48KRLG6N1bzDqDB for ; Sat, 15 Feb 2020 21:28:54 +1100 (AEDT) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 48KRLB1c3fz9tyyZ; Sat, 15 Feb 2020 11:28:50 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=BnhPxxwg; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id ARysyOedZXtY; Sat, 15 Feb 2020 11:28:50 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 48KRLB05Yjz9tyyJ; Sat, 15 Feb 2020 11:28:50 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1581762530; bh=NxZ/EEN3UIzFbam5JKvmthJ2wdWdBJ+t727AFltk1wY=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=BnhPxxwg/BWxyZ79iWEyl6Z2P7nxaIVk52OsjJO17tBDMh0vWNXK3Xsfim3rEZ1Jh AG88JBCVo509kzOYJP70ymFk1NJKdxe8DcDNYuQCdUXMDT9L5Oug1hb8unvVxs9sSc /oI5enUOInNNW317ByNdARatUQNxt6btfE30h1SY= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 176B38B781; Sat, 15 Feb 2020 11:28:51 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id wRXuiH5gmATb; Sat, 15 Feb 2020 11:28:50 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 18D698B755; Sat, 15 Feb 2020 11:28:50 +0100 (CET) Subject: Re: [PATCH] powerpc/kprobes: Fix trap address when trap happened in real mode To: Masami Hiramatsu References: <20200214225434.464ec467ad9094961abb8ddc@kernel.org> From: Christophe Leroy Message-ID: Date: Sat, 15 Feb 2020 11:28:49 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200214225434.464ec467ad9094961abb8ddc@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Anil S Keshavamurthy , Paul Mackerras , stable@kernel.vger.org, "Naveen N. Rao" , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , Larry Finger Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi, Le 14/02/2020 à 14:54, Masami Hiramatsu a écrit : > Hi, > > On Fri, 14 Feb 2020 12:47:49 +0000 (UTC) > Christophe Leroy wrote: > >> When a program check exception happens while MMU translation is >> disabled, following Oops happens in kprobe_handler() in the following >> test: >> >> } else if (*addr != BREAKPOINT_INSTRUCTION) { > > Thanks for the report and patch. I'm not so sure about powerpc implementation > but at where the MMU translation is disabled, can the handler work correctly? > (And where did you put the probe on?) > > Your fix may fix this Oops, but if the handler needs special care, it is an > option to blacklist such place (if possible). I guess that's another story. Here we are not talking about a place where kprobe has been illegitimately activated, but a place where there is a valid trap, which generated a valid 'program check exception'. And kprobe was off at that time. As any 'program check exception' due to a trap (ie a BUG_ON, a WARN_ON, a debugger breakpoint, a perf breakpoint, etc...) calls kprobe_handler(), kprobe_handler() must be prepared to handle the case where the MMU translation is disabled, even if probes are not supposed to be set for functions running with MMU translation disabled. Christophe > > Anyway, Naveen, can you review it? > > Thank you, > >> >> [ 33.098554] BUG: Unable to handle kernel data access on read at 0x0000e268 >> [ 33.105091] Faulting instruction address: 0xc000ec34 >> [ 33.110010] Oops: Kernel access of bad area, sig: 11 [#1] >> [ 33.115348] BE PAGE_SIZE=16K PREEMPT CMPC885 >> [ 33.119540] Modules linked in: >> [ 33.122591] CPU: 0 PID: 429 Comm: cat Not tainted 5.6.0-rc1-s3k-dev-00824-g84195dc6c58a #3267 >> [ 33.131005] NIP: c000ec34 LR: c000ecd8 CTR: c019cab8 >> [ 33.136002] REGS: ca4d3b58 TRAP: 0300 Not tainted (5.6.0-rc1-s3k-dev-00824-g84195dc6c58a) >> [ 33.144324] MSR: 00001032 CR: 2a4d3c52 XER: 00000000 >> [ 33.150699] DAR: 0000e268 DSISR: c0000000 >> [ 33.150699] GPR00: c000b09c ca4d3c10 c66d0620 00000000 ca4d3c60 00000000 00009032 00000000 >> [ 33.150699] GPR08: 00020000 00000000 c087de44 c000afe0 c66d0ad0 100d3dd6 fffffff3 00000000 >> [ 33.150699] GPR16: 00000000 00000041 00000000 ca4d3d70 00000000 00000000 0000416d 00000000 >> [ 33.150699] GPR24: 00000004 c53b6128 00000000 0000e268 00000000 c07c0000 c07bb6fc ca4d3c60 >> [ 33.188015] NIP [c000ec34] kprobe_handler+0x128/0x290 >> [ 33.192989] LR [c000ecd8] kprobe_handler+0x1cc/0x290 >> [ 33.197854] Call Trace: >> [ 33.200340] [ca4d3c30] [c000b09c] program_check_exception+0xbc/0x6fc >> [ 33.206590] [ca4d3c50] [c000e43c] ret_from_except_full+0x0/0x4 >> [ 33.212392] --- interrupt: 700 at 0xe268 >> [ 33.270401] Instruction dump: >> [ 33.273335] 913e0008 81220000 38600001 3929ffff 91220000 80010024 bb410008 7c0803a6 >> [ 33.280992] 38210020 4e800020 38600000 4e800020 <813b0000> 6d2a7fe0 2f8a0008 419e0154 >> [ 33.288841] ---[ end trace 5b9152d4cdadd06d ]--- >> >> Check MSR and convert regs->nip to virtual address if the trap >> happened with MSR_IR cleared. >> >> Reported-by: Larry Finger >> Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly") >> Cc: stable@kernel.vger.org >> Cc: Naveen N. Rao >> Signed-off-by: Christophe Leroy >> >> --- >> The bug might have existed even before that commit from Naveen. >> >> Signed-off-by: Christophe Leroy >> --- >> arch/powerpc/kernel/kprobes.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c >> index 2d27ec4feee4..f8b848aa65bd 100644 >> --- a/arch/powerpc/kernel/kprobes.c >> +++ b/arch/powerpc/kernel/kprobes.c >> @@ -23,6 +23,7 @@ >> #include >> #include >> #include >> +#include >> #include >> >> DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; >> @@ -264,6 +265,9 @@ int kprobe_handler(struct pt_regs *regs) >> if (user_mode(regs)) >> return 0; >> >> + if (!(regs->msr & MSR_IR)) >> + addr = phys_to_virt(regs->nip); >> + >> /* >> * We don't want to be preempted for the entire >> * duration of kprobe processing >> -- >> 2.25.0 >> > >