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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 31C0AC433E0 for ; Fri, 8 Jan 2021 11:48:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA5A5239E7 for ; Fri, 8 Jan 2021 11:48:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727227AbhAHLsJ (ORCPT ); Fri, 8 Jan 2021 06:48:09 -0500 Received: from mx2.suse.de ([195.135.220.15]:52512 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727090AbhAHLsI (ORCPT ); Fri, 8 Jan 2021 06:48:08 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1610106441; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=cRs14sUKQFDtfxfOv42U2R1ffmk3k5kFywb1nQwYHDc=; b=Nw8SdwvSoRzqFvf51E98pVV82XwTvggeDVESclI9UaaVfT4L3bWYUUeoPPb7rdpQmSCR7W u/Ju5CnbypZ1jUgoP4IxGpKtyfQGoydMXiIXo+GT1eoKSxnEA3JYZw8paWmJZVeeokBcRJ UhvGSdL0ZtYC2VDPr74quplkTocELFw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2D8F2AD24; Fri, 8 Jan 2021 11:47:21 +0000 (UTC) Date: Fri, 8 Jan 2021 12:47:18 +0100 From: Michal Hocko To: Xiaoming Ni Cc: linux-kernel@vger.kernel.org, mcgrof@kernel.org, keescook@chromium.org, yzaikin@google.com, adobriyan@gmail.com, linux-fsdevel@vger.kernel.org, vbabka@suse.cz, akpm@linux-foundation.org, wangle6@huawei.com Subject: Re: [PATCH v2] proc_sysctl: fix oops caused by incorrect command parameters. Message-ID: <20210108114718.GA13207@dhcp22.suse.cz> References: <20210108023339.55917-1-nixiaoming@huawei.com> <20210108092145.GX13207@dhcp22.suse.cz> <829bbba0-d3bb-a114-af81-df7390082958@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <829bbba0-d3bb-a114-af81-df7390082958@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 08-01-21 18:01:52, Xiaoming Ni wrote: > On 2021/1/8 17:21, Michal Hocko wrote: > > On Fri 08-01-21 10:33:39, Xiaoming Ni wrote: > > > The process_sysctl_arg() does not check whether val is empty before > > > invoking strlen(val). If the command line parameter () is incorrectly > > > configured and val is empty, oops is triggered. > > > > > > For example, "hung_task_panic=1" is incorrectly written as "hung_task_panic". > > > > > > log: > > > Kernel command line: .... hung_task_panic > > > .... > > > [000000000000000n] user address but active_mm is swapper > > > Internal error: Oops: 96000005 [#1] SMP > > > Modules linked in: > > > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.10.1 #1 > > > Hardware name: linux,dummy-virt (DT) > > > pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--) > > > pc : __pi_strlen+0x10/0x98 > > > lr : process_sysctl_arg+0x1e4/0x2ac > > > sp : ffffffc01104bd40 > > > x29: ffffffc01104bd40 x28: 0000000000000000 > > > x27: ffffff80c0a4691e x26: ffffffc0102a7c8c > > > x25: 0000000000000000 x24: ffffffc01104be80 > > > x23: ffffff80c22f0b00 x22: ffffff80c02e28c0 > > > x21: ffffffc0109f9000 x20: 0000000000000000 > > > x19: ffffffc0107c08de x18: 0000000000000003 > > > x17: ffffffc01105d000 x16: 0000000000000054 > > > x15: ffffffffffffffff x14: 3030253078413830 > > > x13: 000000000000ffff x12: 0000000000000000 > > > x11: 0101010101010101 x10: 0000000000000005 > > > x9 : 0000000000000003 x8 : ffffff80c0980c08 > > > x7 : 0000000000000000 x6 : 0000000000000002 > > > x5 : ffffff80c0235000 x4 : ffffff810f7c7ee0 > > > x3 : 000000000000043a x2 : 00bdcc4ebacf1a54 > > > x1 : 0000000000000000 x0 : 0000000000000000 > > > Call trace: > > > __pi_strlen+0x10/0x98 > > > parse_args+0x278/0x344 > > > do_sysctl_args+0x8c/0xfc > > > kernel_init+0x5c/0xf4 > > > ret_from_fork+0x10/0x30 > > > Code: b200c3eb 927cec01 f2400c07 54000301 (a8c10c22) > > > > > > Fixes: 3db978d480e2843 ("kernel/sysctl: support setting sysctl parameters > > > from kernel command line") > > > Signed-off-by: Xiaoming Ni > > > > Thanks for catching this! > > > > > --------- > > > v2: > > > Added log output of the failure branch based on the review comments of Kees Cook. > > > v1: https://lore.kernel.org/lkml/20201224074256.117413-1-nixiaoming@huawei.com/ > > > --------- > > > --- > > > fs/proc/proc_sysctl.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c > > > index 317899222d7f..dc1a56515e86 100644 > > > --- a/fs/proc/proc_sysctl.c > > > +++ b/fs/proc/proc_sysctl.c > > > @@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char *val, > > > loff_t pos = 0; > > > ssize_t wret; > > > + if (!val) { > > > + pr_err("Missing param value! Expected '%s=...value...'\n", param); > > > + return 0; > I may need to move the validation code for val to the end of the validation > code for param to prevent non-sysctl arguments from triggering the current > print. Why would that matter? A missing value is clearly a error path and it should be reported. > Or delete the print and keep it silent for a little better performance. > Which is better? I do not think there is a performance argument on the table. The generic code is returning EINVAL on a missing value where it is needed. Sysctl all require a value IIRC so EINVAL would be the right way to report this and let the generic code to complain. -- Michal Hocko SUSE Labs