* question about blkio_get_stat()
@ 2012-04-02 13:54 Dan Carpenter
2012-04-07 8:28 ` Jan Kara
0 siblings, 1 reply; 2+ messages in thread
From: Dan Carpenter @ 2012-04-02 13:54 UTC (permalink / raw)
To: Divyesh Shah; +Cc: Jens Axboe, linux-kernel
Hi Divyesh,
Smatch complains that we go outside the array in blkio_get_stat().
block/blk-cgroup.c
731 if (type == BLKIO_STAT_DEQUEUE)
^^^^^^^^^^^^^^^^^^^^^^^^^^
BLKIO_STAT_DEQUEUE is 9.
732 return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
733 blkg->stats.dequeue, cb, dev);
734 #endif
735
736 for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
737 sub_type++) {
738 blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
739 cb->fill(cb, key_str, blkg->stats.stat_arr[type][sub_type]);
^^^^^^^^^^^^^^^^^^^^
This array only has 4 elements and if "type" is 9 we're past the end of
array.
740 }
It's odd that Smatch only started complaining about this now, but this
code has been there for years. I'm puzzled by what changed. Sorry if
there is something obvious I have missed.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: question about blkio_get_stat()
2012-04-02 13:54 question about blkio_get_stat() Dan Carpenter
@ 2012-04-07 8:28 ` Jan Kara
0 siblings, 0 replies; 2+ messages in thread
From: Jan Kara @ 2012-04-07 8:28 UTC (permalink / raw)
To: Dan Carpenter; +Cc: Divyesh Shah, Jens Axboe, linux-kernel
Hi,
On Mon 02-04-12 16:54:56, Dan Carpenter wrote:
> Smatch complains that we go outside the array in blkio_get_stat().
>
> block/blk-cgroup.c
> 731 if (type == BLKIO_STAT_DEQUEUE)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^
> BLKIO_STAT_DEQUEUE is 9.
>
> 732 return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
> 733 blkg->stats.dequeue, cb, dev);
> 734 #endif
> 735
> 736 for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
> 737 sub_type++) {
> 738 blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
> 739 cb->fill(cb, key_str, blkg->stats.stat_arr[type][sub_type]);
> ^^^^^^^^^^^^^^^^^^^^
> This array only has 4 elements and if "type" is 9 we're past the end of
> array.
>
> 740 }
>
> It's odd that Smatch only started complaining about this now, but this
> code has been there for years. I'm puzzled by what changed. Sorry if
> there is something obvious I have missed.
It seems that BLKIO_STAT_... values larger than BLK_IO_STAT_QUEUE are
defined only if CONFIG_DEBUG_BLK_CGROUP is defined. And in that case they
are also handled by blkio_get_stat() in a special way so we never get to
computing blkg->stats.stat_arr[type][sub_type]. So everything seems fine.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 2+ messages in thread
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