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 40B3FC433E0 for ; Fri, 8 Jan 2021 09:23:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0112E22BEA for ; Fri, 8 Jan 2021 09:23:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728231AbhAHJWg (ORCPT ); Fri, 8 Jan 2021 04:22:36 -0500 Received: from mx2.suse.de ([195.135.220.15]:48696 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728183AbhAHJWe (ORCPT ); Fri, 8 Jan 2021 04:22:34 -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=1610097707; 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=JufPMU+Z5aR6Jq7ic5Qmbg6VVDO0Iuq2jNr22wPn5iw=; b=cBm6D/5oAs+bA8Z6AMyV9IXMZYJ0/WHmfIYxKdIDNbu5PCAPETyycJVL/pipG2FAB/SyIb fmHWV3oR6BiVTkbNwBYlrn6Ka8xmHsqpdxVKYYIA6pSS1iugshjPVYD5V2OrRcwNDdf8i+ X1St1s7PG1OiOYcF+ugUj8cPhE9TX4U= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7B563AFBF; Fri, 8 Jan 2021 09:21:47 +0000 (UTC) Date: Fri, 8 Jan 2021 10:21:45 +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: <20210108092145.GX13207@dhcp22.suse.cz> References: <20210108023339.55917-1-nixiaoming@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210108023339.55917-1-nixiaoming@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; > + } Shouldn't you return an error here? Also my understanding is that parse_args is responsible for reporting the error. > + > if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) { > param += sizeof("sysctl") - 1; > > -- > 2.27.0 -- Michal Hocko SUSE Labs