Re: [PATCH] linux: Fallback to fork and exec for clone fail on posix_spawn (BZ#29115)

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 02/05/2022 17:02, Alexey Izbyshev wrote:
> On 2022-05-02 22:57, Adhemerval Zanella wrote:
>> On 02/05/2022 16:42, Adhemerval Zanella wrote:
>>>
>>>
>>> On 02/05/2022 16:15, Alexey Izbyshev wrote:
>>>> Shouldn't also __spawni_child() check whether posix_spawn actions are trying to do something with the error pipe write end (e.g. to close it, to dup() it or dup2() over it, etc.) and prevent that?
>>>
>>> Yeah we should, we need to either duplicate the file descriptor if a file operation
>>> might clobber it and return EBADF for dup2 file action.
>>
>> And using a pipe brings another issue with closefrom where the file action might
>> close the pipe's end and using a dup will help much (since we can not be sure
>> if the duplicate file descriptor will be lower than the closefrom value).  Maybe
>> using mmap with MAP_SHARED would be better here.
> 
> But closefrom() is implemented via close_range() on Linux, so can we just close_range(start, pipe_fd - 1) and close_range(pipe_fd + 1, INT_MAX)? (Ignoring edge conditions here).

It should work indeed.