[PATCH] posix: Handle negative fds in spawn's addfchdir

[Lucas]

Thanks for the quick review!

I initially used (fd < 0) but when I realized other factions functions used

__spawn_valid_fd I told myself that it was the surely the way to go.

Anyway, I sent a v2 that uses (fd < 0) instead.

Lucas

On 3/25/26 19:27, Collin Funk wrote:
> Lucas Chollet <lucas.chollet@free.fr> writes:
>
>> Hello all,
>> This is my first contribution here, so I hope I got everything right.
>> I tested this patch on my Linux x86_64 machine with `make check` and
>> got no regressions compared to master.
>>
>> 8<
>>
>> This patch makes `posix_spawn_file_actions_addfchdir` return EBADF on
>> negative file descriptors. This is mandated by POSIX and similar to what
>> is already done in addopen/addclose.
>>
>> Signed-off-by: Lucas Chollet <lucas.chollet@free.fr>
>> ---
>>   posix/spawn_faction_addfchdir.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/posix/spawn_faction_addfchdir.c b/posix/spawn_faction_addfchdir.c
>> index a3df6df489..b51139a61f 100644
>> --- a/posix/spawn_faction_addfchdir.c
>> +++ b/posix/spawn_faction_addfchdir.c
>> @@ -28,6 +28,9 @@ posix_spawn_file_actions_addfchdir_np (posix_spawn_file_actions_t *actions,
>>   {
>>     struct __spawn_action *rec;
>>   
>> +  if (!__spawn_valid_fd (fd))
>> +    return EBADF;
>> +
>>     /* Allocate more memory if needed.  */
>>     if (actions->__used == actions->__allocated
>>         && __posix_spawn_file_actions_realloc (actions) != 0)
> Thank you for the patch!
>
> However, I want to note here that __spawn_valid_fd() checks if the file
> descriptor is greater than getdtablesize(). Using it here, along with
> some (all?) other places it is used, is incorrect. POSIX states [1]:
>
>      [EBADF]
>          The value specified by fildes is negative.
>
>      It shall not be considered an error for the path or fildes argument
>      passed to these functions to specify a pathname or file descriptor
>      for which the specified operation could not be performed at the time
>      of the call. Any such error shall be detected when the associated
>      file actions object is later used during a posix_spawn() or
>      posix_spawnp() operation.
>
> I noticed glibc's misbehavior when working on Gnulib last year, but
> evidently forgot to fix it...
>
> Collin
>
> [1] https://pubs.opengroup.org/onlinepubs/9799919799/functions/posix_spawn_file_actions_addchdir.html
> [2] https://lists.gnu.org/archive/html/bug-gnulib/2025-10/msg00118.html