On 05/27/2013 04:34 PM, Geert Uytterhoeven wrote:
>> Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
>> > ---
>> > arch/s390/appldata/appldata_base.c | 5 +++--
>> > 1 files changed, 3 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
>> > index bae0f40..566ea87 100644
>> > --- a/arch/s390/appldata/appldata_base.c
>> > +++ b/arch/s390/appldata/appldata_base.c
>> > @@ -212,7 +212,8 @@ appldata_timer_handler(ctl_table *ctl, int write,
>> > return 0;
>> > }
>> > if (!write) {
>> > - len = sprintf(buf, appldata_timer_active ? "1\n" : "0\n");
> Before, len was always 2. The string was zero-terminated but the zero was
> not returned to user space, which is OK.
>
I guess, the original API did not treat it as a zero-terminated string,
it is more like a 'protocol' contents for 'write' or '!write' between
kernel mode and user mode.
At least the kernel did not treat it as a zero-terminated string, we can
reference the '!write' work flow to know about it.
>> > + len = strncpy(buf, appldata_timer_active ? "1\n" : "0\n",
>> > + sizeof(buf));
> Oops, strncpy() doesn't return a size, but a pointer! So this doesn't work.
> I guess you haven't compiled this?
> http://kernel.org/pub/tools/crosstool/files/bin/
>
Oh, it is my fault, I need compile it for a basic checking.
>> > if (len > *lenp)
>> > len = *lenp;
>> > if (copy_to_user(buffer, buf, len))
> What about creating a "uprintf()" that formats strings to a userspace buffer?
>
Hmm... maybe it is a good idea for processing the zero-terminated string
from kernel mode to user mode, but I guess, for our case, it is not a
zero-terminated string, so...
All together, thank you very much for your checking, I should send patch v2.
Thanks.
--
Chen Gang
Asianux Corporation
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