On 22.04.2015 03:26, Peter Chen wrote: > On Tue, Apr 21, 2015 at 09:25:41PM +0200, Heinrich Schuchardt wrote: >> 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@xxxxxx> >>>> --- >>>> 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). > > Sorry, two lines of min_t(..)? Why I can't find it? Hello Peter, in my patch I write: count = min_t(size_t, sizeof(buf) - 1, count); if (copy_from_user(buf, ubuf, count)) return -EFAULT; /* sscanf requires a zero terminated string */ buf[count] = 0; Without the first part of the change I would have had to write: if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count))) return -EFAULT; /* sscanf requires a zero terminated string */ buf[min_t(size_t, sizeof(buf) - 1, count)] = 0; We should do the same calculation "min_t(size_t, sizeof(buf) - 1, count)" only once in the coding. Best regards Heinrich > > >> >> 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; >>>> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
