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SubjectRe: [PATCH 1/1] drivers/usb/chipidea/debuc.c: avoid out of bound read
Hello Peter,

thanks for reviewing.

On 21.04.2015 03:32, Peter Chen wrote:
> On Fri, Apr 17, 2015 at 08:04:13AM +0200, Heinrich Schuchardt wrote:
>> A string written by the user may not be zero terminated.
>>
>> sscanf may read memory beyond the buffer if no zero byte
>> is found.
>>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
>> ---
>> drivers/usb/chipidea/debug.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/chipidea/debug.c b/drivers/usb/chipidea/debug.c
>> index dfb05ed..ef08af3 100644
>> --- a/drivers/usb/chipidea/debug.c
>> +++ b/drivers/usb/chipidea/debug.c
>> @@ -88,9 +88,13 @@ static ssize_t ci_port_test_write(struct file *file, const char __user *ubuf,
>> char buf[32];
>> int ret;
>>
>> - if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
>> + count = min_t(size_t, sizeof(buf) - 1, count);
>> + if (copy_from_user(buf, ubuf, count))
>> return -EFAULT;
>
> Any reasons to change above?

Otherwise we would have two lines with the term
min_t(size_t, sizeof(buf) - 1, count).

This would make the code harder to read.

>>
>> + /* sscanf requires a zero terminated string */
>> + buf[count] = 0;
>> +
>
> I prefer using '\0'

If you confirm the rest of the patch is ok, I will send an updated patch.

Best regards

Heinrich

>
>> if (sscanf(buf, "%u", &mode) != 1)
>> return -EINVAL;
>>



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