Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

subprocess may incorrectly redirect a low fd to stderr if another low fd is closed #77025

Closed
izbyshev mannequin opened this issue Feb 14, 2018 · 5 comments
Closed

subprocess may incorrectly redirect a low fd to stderr if another low fd is closed #77025

izbyshev mannequin opened this issue Feb 14, 2018 · 5 comments
Labels
3.7 (EOL) end of life extension-modules C modules in the Modules dir stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

Comments

@izbyshev
Copy link
Mannequin

izbyshev mannequin commented Feb 14, 2018

BPO 32844
Nosy @gpshead, @izbyshev, @miss-islington
PRs
  • bpo-32844: subprocess: Fix a potential misredirection of a low fd to stderr #5689
  • [3.7] bpo-32844: Fix a subprocess misredirection of a low fd (GH5689) #6262
  • [3.6] bpo-32844: Fix a subprocess misredirection of a low fd (GH5689) #6263
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

    Show more details

    GitHub fields:

    assignee = None
closed_at = <Date 2018-03-26.21:03:05.987>
created_at = <Date 2018-02-14.21:10:48.727>
labels = ['extension-modules', 'type-bug', 'library', '3.7']
title = 'subprocess may incorrectly redirect a low fd to stderr if another low fd is closed'
updated_at = <Date 2018-03-26.21:03:05.986>
user = 'https://github.com/izbyshev'

    bugs.python.org fields:

    activity = <Date 2018-03-26.21:03:05.986>
actor = 'izbyshev'
assignee = 'none'
closed = True
closed_date = <Date 2018-03-26.21:03:05.987>
closer = 'izbyshev'
components = ['Extension Modules', 'Library (Lib)']
creation = <Date 2018-02-14.21:10:48.727>
creator = 'izbyshev'
dependencies = []
files = []
hgrepos = []
issue_num = 32844
keywords = ['patch']
message_count = 5.0
messages = ['312181', '312182', '314478', '314479', '314481']
nosy_count = 3.0
nosy_names = ['gregory.p.smith', 'izbyshev', 'miss-islington']
pr_nums = ['5689', '6262', '6263']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32844'
versions = ['Python 3.6', 'Python 3.7']
    @izbyshev
    Copy link
    Mannequin Author

    izbyshev mannequin commented Feb 14, 2018

    When redirecting, subprocess attempts to achieve the following state: each fd to be redirected to is less than or equal to the fd it is redirected from, which is necessary because redirection occurs in the ascending order of destination descriptors. It fails to do so if a low fd (< 2) is redirected to stderr and another low fd is closed, which may lead to an incorrect redirection, for example:

    $ cat test.py
import os
import subprocess
import sys
    os.close(0)

    subprocess.call([sys.executable, '-c',
    'import sys; print("Hello", file=sys.stderr)'],
    stdin=2,
    stderr=1)

    $ python3 test.py 2>/dev/null
$ python3 test.py >/dev/null
Hello

    Expected behavior:
    $ python3 test.py >/dev/null
    $ python3 test.py 2>/dev/null
    Hello

    @izbyshev izbyshev mannequin added 3.7 (EOL) end of life extension-modules C modules in the Modules dir stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Feb 14, 2018
    @izbyshev
    Copy link
    Mannequin Author

    izbyshev mannequin commented Feb 14, 2018

    Note that the PR doesn't attempt to fix leaking of low dup'ed fds to the child. I'll file a separate report for that in a while.

    @gpshead
    Copy link
    Member

    gpshead commented Mar 26, 2018

    New changeset 0e7144b by Gregory P. Smith (Alexey Izbyshev) in branch 'master':
    bpo-32844: Fix a subprocess misredirection of a low fd (GH5689)
    0e7144b

    @miss-islington
    Copy link
    Contributor

    New changeset 0545563 by Miss Islington (bot) in branch '3.7':
    bpo-32844: Fix a subprocess misredirection of a low fd (GH5689)
    0545563

    @miss-islington
    Copy link
    Contributor

    New changeset 57db13e by Miss Islington (bot) in branch '3.6':
    bpo-32844: Fix a subprocess misredirection of a low fd (GH5689)
    57db13e

    @izbyshev izbyshev mannequin closed this as completed Mar 26, 2018
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
    Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
    Assignees
    No one assigned
    Labels
    3.7 (EOL) end of life extension-modules C modules in the Modules dir stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error
    Projects
    None yet
    Milestone
    No milestone
    Development

    No branches or pull requests
    2 participants
    @gpshead @miss-islington