From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757475Ab3DXHEk (ORCPT ); Wed, 24 Apr 2013 03:04:40 -0400 Received: from intranet.asianux.com ([58.214.24.6]:64560 "EHLO intranet.asianux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755525Ab3DXHEj (ORCPT ); Wed, 24 Apr 2013 03:04:39 -0400 X-Spam-Score: -100.8 Message-ID: <517783D8.6010701@asianux.com> Date: Wed, 24 Apr 2013 15:03:52 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Vasant Hegde CC: Benjamin Herrenschmidt , "sfr@canb.auug.org.au" , "linux-kernel@vger.kernel.org" , "paulus@samba.org" , Al Viro , "linuxppc-dev@lists.ozlabs.org" Subject: Re: [PATCH] PowerPC: kernel: memory access violation when rtas_data_buf contents are more than 1026 References: <516F7A7D.60206@asianux.com> <1366677081.2886.7.camel@pasglop> <5175E85F.1040509@asianux.com> <5175FC36.4060308@asianux.com> <51777B74.8040204@linux.vnet.ibm.com> In-Reply-To: <51777B74.8040204@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2013年04月24日 14:28, Vasant Hegde wrote: > On 04/23/2013 08:42 AM, Chen Gang wrote: >> >> need set '\0' for 'local_buffer'. >> >> SPLPAR_MAXLENGTH is 1026, RTAS_DATA_BUF_SIZE is 4096. so the contents of >> rtas_data_buf may truncated in memcpy. >> >> if contents are really truncated. >> the splpar_strlen is more than 1026. the next while loop checking will >> not find the end of buffer. that will cause memory access violation. >> > > Per parameter length in ibm,get-system-parameter RTAS call is limited to > 1026 bytes (1024 bytes of data + 2 bytes length). And 'rtas_data_buf' > was set to 0 (first 1026 bytes) before call RTAS call. At the worst if > we get junk in RTAS output length field helps to exit from the while > loop. So I don't think we need this patch. Is get-system-parameter return the NUL terminated string ? if so, it will no issue (just like your discription). If it will not return NUL terminated string, please see line 326: "while ((*local_buffer) && (idx < splpar_strlen))" (when idx == 1024, *local_buffer is memory access violation). Since we use the first 2 bytes as length, and also be sure of the real length will never more than 1024, I suggest to: ---------------------------patch begin-------------------------------- diff --git a/arch/powerpc/kernel/lparcfg.c b/arch/powerpc/kernel/lparcfg.c index 801a757..f8bd7cf 100644 --- a/arch/powerpc/kernel/lparcfg.c +++ b/arch/powerpc/kernel/lparcfg.c @@ -323,7 +323,7 @@ static void parse_system_parameter_string(struct seq_file *m) w_idx = 0; idx = 0; - while ((*local_buffer) && (idx < splpar_strlen)) { + while (idx < splpar_strlen) { workbuffer[w_idx++] = local_buffer[idx++]; if ((local_buffer[idx] == ',') || (local_buffer[idx] == '\0')) { ---------------------------patch end---------------------------------- Thanks. -- Chen Gang Asianux Corporation