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On 27/01/16 11:42, James Hogan wrote:
> Hi Colin,
>
> On Tue, Jan 26, 2016 at 11:37:25PM +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>
>> number_written is not initialized, so it can be any value. In the
>> case where dport->xmit_cnt is zero, number_written is not set
>> and subsequent accesses to it will be reading a garbage value.
>
> the only subsequent accesses when dport->xmit_cnt == 0 are:
>
> /* if we've made more data available, wake up tty */
> if (count && number_written) {
>
> and:
>
> /* did the write fail? */
> return count && !number_written;
>
> but dport->xmit_cnt == 0 implies count == 0, so number_written shouldn
't
> be used, and both will evaluate to false regardless of the uninitialis
ed
> value, so it looks fine as it is to me.
>
> Is this tripping up some static analysis tool or something?
It was found using cppcheck, namely:
[drivers/tty/metag_da.c:269]: (error) Uninitialized variable: number_wri
tten
>
> Thanks
> James
>
>> Fix this by initializing it to zero for the case when
>> dport->xmit_count is zero.
>>
>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>> ---
>> drivers/tty/metag_da.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/tty/metag_da.c b/drivers/tty/metag_da.c
>> index 9325262..3da89c1 100644
>> --- a/drivers/tty/metag_da.c
>> +++ b/drivers/tty/metag_da.c
>> @@ -230,7 +230,7 @@ static int put_channel_data(unsigned int chan)
>> {
>> struct dashtty_port *dport;
>> struct tty_struct *tty;
>> - int number_written;
>> + int number_written = 0;
>> unsigned int count = 0;
>>
>> dport = &dashtty_ports[chan];
>> --
>> 2.7.0.rc3
>>
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