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Message-ID: <1366677081.2886.7.camel@pasglop>
Date: Tue, 23 Apr 2013 10:31:21 +1000
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: Chen Gang <gang.chen@...anux.com>
Cc: "paulus@...ba.org" <paulus@...ba.org>,
Al Viro <viro@...iv.linux.org.uk>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Michael Ellerman <michael@...erman.id.au>,
"sfr@...b.auug.org.au" <sfr@...b.auug.org.au>
Subject: Re: [Suggestion] PowerPC: kernel: memory access violation when
rtas_data_buf contents are more than 1026
On Thu, 2013-04-18 at 12:45 +0800, Chen Gang wrote:
> Hello Maintainers:
>
>
> in arch/powerpc/kernel/lparcfg.c, parse_system_parameter_string()
>
> need set '\0' for 'local_buffer'.
>
> the reason is:
> SPLPAR_MAXLENGTH is 1026, RTAS_DATA_BUF_SIZE is 4096
> the contents of rtas_data_buf may truncated in memcpy (line 301).
>
> if contents are truncated.
> the splpar_strlen is more than 1026 (line 321)
> the while loop checking will not find the end of buffer (line 326)
> it will cause memory access violation.
>
>
> I find it by reading code, so please help check.
And a signed-off-by please ?
Cheers,
Ben.
> thanks.
>
> gchen.
>
> -------------------------related fix patch--------------------------------------
>
> diff --git a/arch/powerpc/kernel/lparcfg.c b/arch/powerpc/kernel/lparcfg.c
> index 801a757..d92f387 100644
> --- a/arch/powerpc/kernel/lparcfg.c
> +++ b/arch/powerpc/kernel/lparcfg.c
> @@ -299,6 +299,7 @@ static void parse_system_parameter_string(struct seq_file *m)
> __pa(rtas_data_buf),
> RTAS_DATA_BUF_SIZE);
> memcpy(local_buffer, rtas_data_buf, SPLPAR_MAXLENGTH);
> + local_buffer[SPLPAR_MAXLENGTH - 1] = '\0';
> spin_unlock(&rtas_data_buf_lock);
>
> if (call_status != 0) {
>
>
>
> -------------------------related source code------------------------------------
>
>
> 283 static void parse_system_parameter_string(struct seq_file *m)
> 284 {
> 285 int call_status;
> 286
> 287 unsigned char *local_buffer = kmalloc(SPLPAR_MAXLENGTH, GFP_KERNEL);
> 288 if (!local_buffer) {
> 289 printk(KERN_ERR "%s %s kmalloc failure at line %d\n",
> 290 __FILE__, __func__, __LINE__);
> 291 return;
> 292 }
> 293
> 294 spin_lock(&rtas_data_buf_lock);
> 295 memset(rtas_data_buf, 0, SPLPAR_MAXLENGTH);
> 296 call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
> 297 NULL,
> 298 SPLPAR_CHARACTERISTICS_TOKEN,
> 299 __pa(rtas_data_buf),
> 300 RTAS_DATA_BUF_SIZE);
> 301 memcpy(local_buffer, rtas_data_buf, SPLPAR_MAXLENGTH);
> 302 spin_unlock(&rtas_data_buf_lock);
> 303
> 304 if (call_status != 0) {
> 305 printk(KERN_INFO
> 306 "%s %s Error calling get-system-parameter (0x%x)\n",
> 307 __FILE__, __func__, call_status);
> 308 } else {
> 309 int splpar_strlen;
> 310 int idx, w_idx;
> 311 char *workbuffer = kzalloc(SPLPAR_MAXLENGTH, GFP_KERNEL);
> 312 if (!workbuffer) {
> 313 printk(KERN_ERR "%s %s kmalloc failure at line %d\n",
> 314 __FILE__, __func__, __LINE__);
> 315 kfree(local_buffer);
> 316 return;
> 317 }
> 318 #ifdef LPARCFG_DEBUG
> 319 printk(KERN_INFO "success calling get-system-parameter\n");
> 320 #endif
> 321 splpar_strlen = local_buffer[0] * 256 + local_buffer[1];
> 322 local_buffer += 2; /* step over strlen value */
> 323
> 324 w_idx = 0;
> 325 idx = 0;
> 326 while ((*local_buffer) && (idx < splpar_strlen)) {
> 327 workbuffer[w_idx++] = local_buffer[idx++];
> 328 if ((local_buffer[idx] == ',')
> 329 || (local_buffer[idx] == '\0')) {
> 330 workbuffer[w_idx] = '\0';
> 331 if (w_idx) {
> 332 /* avoid the empty string */
> 333 seq_printf(m, "%s\n", workbuffer);
> 334 }
> 335 memset(workbuffer, 0, SPLPAR_MAXLENGTH);
> 336 idx++; /* skip the comma */
> 337 w_idx = 0;
> 338 } else if (local_buffer[idx] == '=') {
> 339 /* code here to replace workbuffer contents
> 340 with different keyword strings */
> 341 if (0 == strcmp(workbuffer, "MaxEntCap")) {
> 342 strcpy(workbuffer,
> 343 "partition_max_entitled_capacity");
> 344 w_idx = strlen(workbuffer);
> 345 }
> 346 if (0 == strcmp(workbuffer, "MaxPlatProcs")) {
> 347 strcpy(workbuffer,
> 348 "system_potential_processors");
> 349 w_idx = strlen(workbuffer);
> 350 }
> 351 }
> 352 }
> 353 kfree(workbuffer);
> 354 local_buffer -= 2; /* back up over strlen value */
> 355 }
> 356 kfree(local_buffer);
> 357 }
--
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