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SubjectRe: [PATCH] i2c: core-smbus: fix a potential uninitialization bug
Hi Wenwen,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on wsa/i2c/for-next]
[also build test ERROR on v4.17-rc3 next-20180504]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Wenwen-Wang/i2c-core-smbus-fix-a-potential-uninitialization-bug/20180505-164208
base: https://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git i2c/for-next
config: x86_64-randconfig-x013-201817 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64

All errors (new ones prefixed by >>):

drivers/i2c/i2c-core-smbus.c: In function 'i2c_smbus_xfer_emulated':
>> drivers/i2c/i2c-core-smbus.c:347:2: error: 'msgbug1' undeclared (first use in this function); did you mean 'msgbuf1'?
msgbug1[0] = 0;
^~~~~~~
msgbuf1
drivers/i2c/i2c-core-smbus.c:347:2: note: each undeclared identifier is reported only once for each function it appears in

vim +347 drivers/i2c/i2c-core-smbus.c

310
311 /*
312 * Simulate a SMBus command using the I2C protocol.
313 * No checking of parameters is done!
314 */
315 static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
316 unsigned short flags,
317 char read_write, u8 command, int size,
318 union i2c_smbus_data *data)
319 {
320 /*
321 * So we need to generate a series of msgs. In the case of writing, we
322 * need to use only one message; when reading, we need two. We
323 * initialize most things with sane defaults, to keep the code below
324 * somewhat simpler.
325 */
326 unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3];
327 unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2];
328 int num = read_write == I2C_SMBUS_READ ? 2 : 1;
329 int i;
330 u8 partial_pec = 0;
331 int status;
332 struct i2c_msg msg[2] = {
333 {
334 .addr = addr,
335 .flags = flags,
336 .len = 1,
337 .buf = msgbuf0,
338 }, {
339 .addr = addr,
340 .flags = flags | I2C_M_RD,
341 .len = 0,
342 .buf = msgbuf1,
343 },
344 };
345
346 msgbuf0[0] = command;
> 347 msgbug1[0] = 0;
348 switch (size) {
349 case I2C_SMBUS_QUICK:
350 msg[0].len = 0;
351 /* Special case: The read/write field is used as data */
352 msg[0].flags = flags | (read_write == I2C_SMBUS_READ ?
353 I2C_M_RD : 0);
354 num = 1;
355 break;
356 case I2C_SMBUS_BYTE:
357 if (read_write == I2C_SMBUS_READ) {
358 /* Special case: only a read! */
359 msg[0].flags = I2C_M_RD | flags;
360 num = 1;
361 }
362 break;
363 case I2C_SMBUS_BYTE_DATA:
364 if (read_write == I2C_SMBUS_READ)
365 msg[1].len = 1;
366 else {
367 msg[0].len = 2;
368 msgbuf0[1] = data->byte;
369 }
370 break;
371 case I2C_SMBUS_WORD_DATA:
372 if (read_write == I2C_SMBUS_READ)
373 msg[1].len = 2;
374 else {
375 msg[0].len = 3;
376 msgbuf0[1] = data->word & 0xff;
377 msgbuf0[2] = data->word >> 8;
378 }
379 break;
380 case I2C_SMBUS_PROC_CALL:
381 num = 2; /* Special case */
382 read_write = I2C_SMBUS_READ;
383 msg[0].len = 3;
384 msg[1].len = 2;
385 msgbuf0[1] = data->word & 0xff;
386 msgbuf0[2] = data->word >> 8;
387 break;
388 case I2C_SMBUS_BLOCK_DATA:
389 if (read_write == I2C_SMBUS_READ) {
390 msg[1].flags |= I2C_M_RECV_LEN;
391 msg[1].len = 1; /* block length will be added by
392 the underlying bus driver */
393 i2c_smbus_try_get_dmabuf(&msg[1], 0);
394 } else {
395 msg[0].len = data->block[0] + 2;
396 if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
397 dev_err(&adapter->dev,
398 "Invalid block write size %d\n",
399 data->block[0]);
400 return -EINVAL;
401 }
402
403 i2c_smbus_try_get_dmabuf(&msg[0], command);
404 for (i = 1; i < msg[0].len; i++)
405 msg[0].buf[i] = data->block[i - 1];
406 }
407 break;
408 case I2C_SMBUS_BLOCK_PROC_CALL:
409 num = 2; /* Another special case */
410 read_write = I2C_SMBUS_READ;
411 if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
412 dev_err(&adapter->dev,
413 "Invalid block write size %d\n",
414 data->block[0]);
415 return -EINVAL;
416 }
417
418 msg[0].len = data->block[0] + 2;
419 i2c_smbus_try_get_dmabuf(&msg[0], command);
420 for (i = 1; i < msg[0].len; i++)
421 msg[0].buf[i] = data->block[i - 1];
422
423 msg[1].flags |= I2C_M_RECV_LEN;
424 msg[1].len = 1; /* block length will be added by
425 the underlying bus driver */
426 i2c_smbus_try_get_dmabuf(&msg[1], 0);
427 break;
428 case I2C_SMBUS_I2C_BLOCK_DATA:
429 if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
430 dev_err(&adapter->dev, "Invalid block %s size %d\n",
431 read_write == I2C_SMBUS_READ ? "read" : "write",
432 data->block[0]);
433 return -EINVAL;
434 }
435
436 if (read_write == I2C_SMBUS_READ) {
437 msg[1].len = data->block[0];
438 i2c_smbus_try_get_dmabuf(&msg[1], 0);
439 } else {
440 msg[0].len = data->block[0] + 1;
441
442 i2c_smbus_try_get_dmabuf(&msg[0], command);
443 for (i = 1; i <= data->block[0]; i++)
444 msg[0].buf[i] = data->block[i];
445 }
446 break;
447 default:
448 dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
449 return -EOPNOTSUPP;
450 }
451
452 i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
453 && size != I2C_SMBUS_I2C_BLOCK_DATA);
454 if (i) {
455 /* Compute PEC if first message is a write */
456 if (!(msg[0].flags & I2C_M_RD)) {
457 if (num == 1) /* Write only */
458 i2c_smbus_add_pec(&msg[0]);
459 else /* Write followed by read */
460 partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
461 }
462 /* Ask for PEC if last message is a read */
463 if (msg[num-1].flags & I2C_M_RD)
464 msg[num-1].len++;
465 }
466
467 status = i2c_transfer(adapter, msg, num);
468 if (status < 0)
469 return status;
470 if (status != num)
471 return -EIO;
472
473 /* Check PEC if last message is a read */
474 if (i && (msg[num-1].flags & I2C_M_RD)) {
475 status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
476 if (status < 0)
477 return status;
478 }
479
480 if (read_write == I2C_SMBUS_READ)
481 switch (size) {
482 case I2C_SMBUS_BYTE:
483 data->byte = msgbuf0[0];
484 break;
485 case I2C_SMBUS_BYTE_DATA:
486 data->byte = msgbuf1[0];
487 break;
488 case I2C_SMBUS_WORD_DATA:
489 case I2C_SMBUS_PROC_CALL:
490 data->word = msgbuf1[0] | (msgbuf1[1] << 8);
491 break;
492 case I2C_SMBUS_I2C_BLOCK_DATA:
493 for (i = 0; i < data->block[0]; i++)
494 data->block[i + 1] = msg[1].buf[i];
495 break;
496 case I2C_SMBUS_BLOCK_DATA:
497 case I2C_SMBUS_BLOCK_PROC_CALL:
498 for (i = 0; i < msg[1].buf[0] + 1; i++)
499 data->block[i] = msg[1].buf[i];
500 break;
501 }
502
503 if (msg[0].flags & I2C_M_DMA_SAFE)
504 kfree(msg[0].buf);
505 if (msg[1].flags & I2C_M_DMA_SAFE)
506 kfree(msg[1].buf);
507
508 return 0;
509 }
510

---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
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