Re: [PATCH][v2] proc: use vmalloc for our kernel buffer

Josef Bacik
2020-08-13T17:36:18Z

On 8/13/20 1:31 PM, Al Viro wrote:
> On Thu, Aug 13, 2020 at 01:19:18PM -0400, Josef Bacik wrote:
>
>>> in sunrpc proc_dodebug() turns into
>>> left -= snprintf(buffer, left, "0x%04x\n",
> ^^^^
> left + 1, that is.
>
>>> *(unsigned int *) table->data);
>>> and that's not the only example.
>>>
>>
>> We wouldn't even need the extra +1 part, since we're only copying in how
>> much the user wants anyway, we could just go ahead and convert this to
>>
>> left -= snprintf(buffer, left, "0x%04x\n", *(unsigned int *) table->data);
>>
>> and be fine, right? Or am I misunderstanding what you're looking for? Thanks,
>
> snprintf() always produces a NUL-terminated string. And if you are passing 7 as
> len, you want 0xf0ad\n to be copied to user. For that you need 8 passed to
> snprintf, and 8-byte buffer given to it.
>

Right, gotcha. I'll rig that up and see how it looks. I'd recommend looking
through what I do with a fine tooth comb, I'm obviously not batting 1000 today.
Thanks,

Josef