Re: [PATCH v4 2/4] posix: Do not clobber errno by atfork handlers

[Florian Weimer <fweimer@redhat.com>]

* Adhemerval Zanella:

> On 24/06/2021 05:19, Florian Weimer wrote:
>> * Adhemerval Zanella via Libc-alpha:
>> 
>>> Checked on x86_64-linux-gnu.
>>> ---
>>>  posix/fork.c | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/posix/fork.c b/posix/fork.c
>>> index 44caf8d166..9340511198 100644
>>> --- a/posix/fork.c
>>> +++ b/posix/fork.c
>>> @@ -103,6 +103,9 @@ __libc_fork (void)
>>>      }
>>>    else
>>>      {
>>> +      /* If _Fork failed, preserve its errno value.  */
>>> +      int save_errno = errno;
>>> +
>>>        /* Release acquired locks in the multi-threaded case.  */
>>>        if (multiple_threads)
>>>  	{
>>> @@ -115,6 +118,8 @@ __libc_fork (void)
>>>  
>>>        /* Run the handlers registered for the parent.  */
>>>        __run_fork_handlers (atfork_run_parent, multiple_threads);
>>> +
>>> +      __set_errno (save_errno);
>> 
>> I think you should restrict the __set_errno call to pid < 0, so that
>> errno is not 0 after a different value has been observed by the fork
>> handlers.
>
> OK, I can change it back.  From the previous review iteration I understood
> you were ok with making it unconditional [1].
>
> [1] https://sourceware.org/pipermail/libc-alpha/2021-March/123729.html

Sorry, I meant making the saving unconditional, not the restoring.

Florian