Re: [PATCH] iio: multiplexer: fix unsigned check with less than zero
From: Colin Ian King
Date: Wed Mar 08 2017 - 04:04:13 EST
On 08/03/17 08:59, Peter Rosin wrote:
> On 2017-03-07 16:06, Colin King wrote:
>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>> Comparing a size_t with less than zero is always false as size_t
>> is unsigned. The intent of the comparison was to check if the size
>> was -1 (that is, undefined), so use that instead.
>> Detected by CoverityScan, CID#1415278 ("Unsigned compared against 0")
>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> Oops, thanks for highlighting this! However, I think I prefer to instead
> change the type of the struct mux_ext_info_cache member 'size' to ssize_t.
> That way, there is no annoying explicit cast. And perhaps add an early
> if (len >= PAGE_SIZE)
> return -EINVAL;
> to mux_write_ext_info (because the sysfs read function in use for iio ext
> info can't handle more than a page anyway, IIUC). That way it is fairly
> certain that the ssize_t type will always be big enough. :-)
Sounds like a far better solution.
> So, I'm going send out a patch like that instead, unless someone happens to
> beat me to it...
>> drivers/iio/multiplexer/iio-mux.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> diff --git a/drivers/iio/multiplexer/iio-mux.c b/drivers/iio/multiplexer/iio-mux.c
>> index 94d40f9b..6c23033 100644
>> --- a/drivers/iio/multiplexer/iio-mux.c
>> +++ b/drivers/iio/multiplexer/iio-mux.c
>> @@ -61,7 +61,7 @@ static int iio_mux_select(struct mux *mux, int idx)
>> cache = &child->ext_info_cache[i];
>> - if (cache->size < 0)
>> + if (cache->size == (size_t)-1)
>> ret = iio_write_channel_ext_info(mux->parent, attr,