Re: [PATCH 16/36] tty/vt: consolemap: check put_user() in con_get_unimap()

Jiri Slaby
2022-06-08T08:12:25Z

On 07. 06. 22, 16:19, Ilpo Järvinen wrote:
> On Tue, 7 Jun 2022, Jiri Slaby wrote:
>
>> Only the return value of copy_to_user() is checked in con_get_unimap().
>> Do the same for put_user() of the count too.
>>
>> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
>> ---
>> drivers/tty/vt/consolemap.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
>> index 831450f2bfd1..92b5dddb00d9 100644
>> --- a/drivers/tty/vt/consolemap.c
>> +++ b/drivers/tty/vt/consolemap.c
>> @@ -813,7 +813,8 @@ int con_get_unimap(struct vc_data *vc, ushort ct, ushort __user *uct,
>> console_unlock();
>> if (copy_to_user(list, unilist, min(ect, ct) * sizeof(*unilist)))
>> ret = -EFAULT;
>> - put_user(ect, uct);
>> + if (put_user(ect, uct))
>> + ret = -EFAULT;
>> kvfree(unilist);
>> return ret ? ret : (ect <= ct) ? 0 : -ENOMEM;
>> }
>>
>
> Doesn't this fix something?

If you mean a Fixes tag, this is pre-git.

If you mean a bug, well, likely yes, users now get informed. But I don't
think anyone cares ;). But who knows, maybe we will start seeing
userspace failures now (as they might not provide writable count field
-- unlikely). That's one of the reasons why I did this as a separate
commit. Let's see if are going to revert this or not...

thanks,
--
js
suse labs