Re: [PATCH] Remove extra unlock for the mutex

Abhinav Singh
2023-10-11T15:50:03Z

On 10/11/23 12:00, Greg KH wrote:
> On Wed, Oct 11, 2023 at 04:16:30AM +0530, Abhinav Singh wrote:
>> There is a double unlock on mutex. This can cause undefined behaviour.
>>
>> Signed-off-by: Abhinav Singh <singhabhinav9051571833@gmail.com>
>> ---
>> net/ipv4/inet_connection_sock.c | 1 -
>> 1 file changed, 1 deletion(-)
>>
>> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
>> index aeebe8816689..f11fe8c727a4 100644
>> --- a/net/ipv4/inet_connection_sock.c
>> +++ b/net/ipv4/inet_connection_sock.c
>> @@ -597,7 +597,6 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
>> }
>> if (head2_lock_acquired)
>> spin_unlock(&head2->lock);
>> - spin_unlock_bh(&head->lock);
>
> How was this tested?
>
> And where is the now-needed unlock of the head->lock?
>
> How was this change found?
>
> And your subject line needs a lot of work...
>
> thanks,
>
> greg k-h
Hello, I used sparse tool and got it this warning message "warning:
context imbalance in 'inet_csk_get_port' - unexpected unlock"
Due to my over excitement of sending a good patch to kernel I didnt see
correctly and misread `head` as `head2` and thought it was double
unlocking the mutex. I m very sorry. But on a different note think we
should do a check for `head->lock` as well before unlocking. Unlocking a
non locked mutex can also trigger a undefined behaviour.

Thank you,
Abhinav Singh