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=-6.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 39489C34031 for ; Wed, 19 Feb 2020 01:03:53 +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 DE55B24655 for ; Wed, 19 Feb 2020 01:03:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="aSDwJ4LP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE55B24655 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 48MfcQ5FmjzDqkT for ; Wed, 19 Feb 2020 12:03:50 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=mhiramat@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=default header.b=aSDwJ4LP; dkim-atps=neutral Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (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 48MfZ25Q3xzDqXg for ; Wed, 19 Feb 2020 12:01:46 +1100 (AEDT) Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AD6D72173E; Wed, 19 Feb 2020 01:01:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582074103; bh=Ubv12rjlONurB1Qtnd719hs/ZObAPh+KuOVjfjcawY0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=aSDwJ4LP1RZutlYlOaBfqFyOBo3drf+frZ+i/2q4Xrr8oUkPkbt4E/1Y0AAACCk5d 4e+/CNI2moVppFHipMygipweZA+whFjCjCVQKPe6nvboJaP/VmP+rEAQYAq0n0g8H+ 8PvQjpl9qrfiqEirP5Yifhj0a68+r7WE1hWAmNfM= Date: Wed, 19 Feb 2020 10:01:39 +0900 From: Masami Hiramatsu To: Christophe Leroy Subject: Re: [PATCH v3] powerpc/kprobes: Ignore traps that happened in real mode Message-Id: <20200219100139.f4dec4bfe5ac1362bf7341bd@kernel.org> In-Reply-To: <424331e2006e7291a1bfe40e7f3fa58825f565e1.1582054578.git.christophe.leroy@c-s.fr> References: <424331e2006e7291a1bfe40e7f3fa58825f565e1.1582054578.git.christophe.leroy@c-s.fr> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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" On Tue, 18 Feb 2020 19:38:27 +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 > code: > > } else if (*addr != BREAKPOINT_INSTRUCTION) { > > [ 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 ]--- > > kprobe is not prepared to handle events in real mode and functions > running in real mode should have been blacklisted, so kprobe_handler() > can safely bail out telling 'this trap is not mine' for any trap that > happened while in real-mode. > > If the trap happened with MSR_IR or MSR_DR cleared, return 0 immediately. > Looks good to me. Reviewed-by: Masami Hiramatsu Thank you! > Reported-by: Larry Finger > Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly") > Cc: stable@vger.kernel.org > Cc: Naveen N. Rao > Cc: Masami Hiramatsu > Signed-off-by: Christophe Leroy > > --- > v3: Also bail out if MSR_DR is cleared. > > Resending v2 with a more appropriate name > > v2: bailing out instead of converting real-time address to virtual and continuing. > > The bug might have existed even before that commit from Naveen. > > Signed-off-by: Christophe Leroy > --- > arch/powerpc/kernel/kprobes.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c > index 2d27ec4feee4..9b340af02c38 100644 > --- a/arch/powerpc/kernel/kprobes.c > +++ b/arch/powerpc/kernel/kprobes.c > @@ -264,6 +264,9 @@ int kprobe_handler(struct pt_regs *regs) > if (user_mode(regs)) > return 0; > > + if (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)) > + return 0; > + > /* > * We don't want to be preempted for the entire > * duration of kprobe processing > -- > 2.25.0 > -- Masami Hiramatsu