On 11/15/24 04:04, David Wei wrote:
> On 2024-11-14 18:50, Luiz Augusto von Dentz wrote:
>> Hi David,
>> On Thu, Nov 14, 2024 at 9:30 PM David Wei <dw@xxxxxxxxxxx> wrote:
>>> On 2024-11-14 18:15, Luiz Augusto von Dentz wrote:
>>>> Hi David,
>>>> On Thu, Nov 14, 2024 at 7:42 PM David Wei <dw@xxxxxxxxxxx> wrote:
>>>>> On 2024-11-14 15:27, Michal Luczaj wrote:
>>>>> ...
>>>>>> diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
>>>>>> index f48250e3f2e103c75d5937e1608e43c123aa3297..1001fb4cc21c0ecc7bcdd3ea9041770ede4f27b8 100644
>>>>>> --- a/net/bluetooth/rfcomm/sock.c
>>>>>> +++ b/net/bluetooth/rfcomm/sock.c
>>>>>> @@ -629,10 +629,9 @@ static int rfcomm_sock_setsockopt_old(struct socket *sock, int optname,
>>>>>>
>>>>>> switch (optname) {
>>>>>> case RFCOMM_LM:
>>>>>> - if (bt_copy_from_sockptr(&opt, sizeof(opt), optval, optlen)) {
>>>>>> - err = -EFAULT;
>>>>>> + err = copy_safe_from_sockptr(&opt, sizeof(opt), optval, optlen);
>>>>>> + if (err)
>>>>>> break;
>>>>>> - }
>>>>>
>>>>> This will return a positive integer if copy_safe_from_sockptr() fails.
>>>>
>>>> What are you talking about copy_safe_from_sockptr never returns a
>>>> positive value:
>>>>
>>>> * Returns:
>>>> * * -EINVAL: @optlen < @ksize
>>>> * * -EFAULT: access to userspace failed.
>>>> * * 0 : @ksize bytes were copied
>>>
>>> Isn't this what this series is about? copy_from_sockptr() returns 0 on
>>> success, or a positive integer for number of bytes NOT copied on error.
>>> Patch 4 even updates the docs for copy_from_sockptr().
>>>
>>> copy_safe_from_sockptr()
>>> -> copy_from_sockptr()
>>> -> copy_from_sockptr_offset()
>>> -> memcpy() for kernel to kernel OR
>>> -> copy_from_user() otherwise
>>
>> Well except the safe version does check what would otherwise cause a
>> positive return by the likes of copy_from_user and returns -EINVAL
>> instead, otherwise the documentation of copy_safe_from_sockptr is just
>> wrong and shall state that it could return positive as well but I
>> guess that would just make it as inconvenient so we might as well
>> detect when a positive value would be returned just return -EFAULT
>> instead.
>
> Yes it checks and returns EINVAL, but not EFAULT which is what my
> comment on the original patch is about. Most of the calls to
> bt_copy_from_sockptr() that Michal replaced with
> copy_safe_from_sockptr() remain incorrect because it is assumed that
> EFAULT is returned. Only rfcomm_sock_setsockopt_old() was vaguely doing
> the right thing and the patch changed it back to the incorrect pattern:
>
> err = copy_safe_from_sockptr(...);
> if (err)
> break;
>
> But I do agree that making copy_safe_from_sockptr() do the right thing
> and EFAULT will be easier and prevent future problems given that
> copy_from_sockptr() is meant to be deprecated anyhow.
Just to be clear: copy_safe_from_sockptr() was recently fixed to return
EFAULT:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=eb94b7bb1010
Sorry, I should have mentioned this series is a follow up to that patch.
Thanks,
Michal
