gh-144023: prevent follow_symlinks from being allowed with an fd of 0

[AZero13]

fd_and_follow_symlinks_invalid lets you use fd and follow_symlinks together if fd is 0.

This is incorrect, as 0 is a valid fd.

• Issue: posixmodule: fd_and_follow_symlinks_invalid lets fd be 0 #144023

[sobolevn]

Is there any way to test this?

[vstinner]

Is there any way to test this?

stat(0) can be be used for example.

Current behavior:

>>> os.stat(1, follow_symlinks=False)
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    os.stat(1, follow_symlinks=False)
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: stat: cannot use fd and follow_symlinks together

>>> os.stat(0, follow_symlinks=False)
os.stat_result(st_mode=8576, st_ino=4, st_dev=27, st_nlink=1, st_uid=1000, st_gid=5, st_size=0, st_atime=1768842168, st_mtime=1768842168, st_ctime=1768841838)

[AZero13]

Is there any way to test this?

stat(0) can be be used for example.

Current behavior:

>>> os.stat(1, follow_symlinks=False)
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    os.stat(1, follow_symlinks=False)
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: stat: cannot use fd and follow_symlinks together

>>> os.stat(0, follow_symlinks=False)
os.stat_result(st_mode=8576, st_ino=4, st_dev=27, st_nlink=1, st_uid=1000, st_gid=5, st_size=0, st_atime=1768842168, st_mtime=1768842168, st_ctime=1768841838)

Thank you!

[serhiy-storchaka]

Good catch. LGTM. 👍

[sobolevn]

Thank you!

[miss-islington-app]

Thanks @AZero13 for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington-app]

Sorry, @AZero13 and @serhiy-storchaka, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker fa44efa0ef1972ac1e2f66996303154be11f605e 3.14

[miss-islington-app]

Sorry, @AZero13 and @serhiy-storchaka, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker fa44efa0ef1972ac1e2f66996303154be11f605e 3.13