gh-98896: Fix parsing issue in resource_tracker to allow shared memory names containing colons #138473

rani-pinchuk · 2025-09-03T19:41:40Z

Shared memory names containing colons were not parsed correctly as the code of resource_tracker assumed that these names contain no colons.

@encukou

Issue: Resource tracker fails to track filenames with colons on Linux #98896

encukou

Hello! Sorry for the delay in reviewing.
The fix looks good for colons, but a comment on the issue also mentioned newlines in filenames. Do you want to tackle that, or leave it to another PR?

Lib/multiprocessing/resource_tracker.py

… the names

rani-pinchuk · 2025-11-05T21:23:10Z

Hi Petr, Thanks for your email (and also the one you sent later) - it is very kind of you. I try to address, indeed, the newlines - by encoding and decoding the shared_memory name. So a different approach than before. See the updated PR. Regards, Rani

…

On Tue, Nov 4, 2025 at 2:56 PM Petr Viktorin ***@***.***> wrote: ***@***.**** commented on this pull request. Hello! Sorry for the delay in reviewing. The lix looks good for colons, but a comment on the issue also mentioned *newlines* in filenames. Do you want to tackle that, or leave it to another PR? ------------------------------ In Lib/multiprocessing/resource_tracker.py <#138473 (comment)>: > + parts = line.strip().decode('ascii').split(':') + if len(parts) < 3: + raise ValueError("malformed resource_tracker message: %r" % (parts,)) + cmd = parts[0] + rtype = parts[-1] + name = ':'.join(parts[1:-1]) How about this? ⬇️ Suggested change - parts = line.strip().decode('ascii').split(':') - if len(parts) < 3: - raise ValueError("malformed resource_tracker message: %r" % (parts,)) - cmd = parts[0] - rtype = parts[-1] - name = ':'.join(parts[1:-1]) + cmd, *name_parts, rtype = line.strip().decode('ascii').split(':') + name = ':'.join(name_parts) — Reply to this email directly, view it on GitHub <#138473 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AH6O62VUX7TDUCM6PR6DYN333CV67AVCNFSM6AAAAACFRVHJJWVHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHMZTIMJWGU4DAOBUGY> . You are receiving this because you authored the thread.Message ID: ***@***.***>

encukou

Thank you!
This approach feels ad-hoc; did you consider a standard encoding like JSON lines or pickle?
(Python's JSON encoder won't output newlines unless you ask for indentation; pickle.load reads one object from a file and stops.)

But I can merge this if you don't want to explore those options.

encukou · 2025-11-06T08:48:40Z

Lib/multiprocessing/resource_tracker.py

-                    cmd, name, rtype = line.strip().decode('ascii').split(':')
+                    cmd, enc_name, rtype = line.rstrip(b'\n').decode('ascii').split(':', 2)
+                    if rtype == "shared_memory":
+                        name = base64.urlsafe_b64decode(enc_name.encode('ascii')).decode('utf-8', 'surrogateescape')


Decoding is OK with strings.

Suggested change

name = base64.urlsafe_b64decode(enc_name.encode('ascii')).decode('utf-8', 'surrogateescape')

name = base64.urlsafe_b64decode(enc_name).decode('utf-8', 'surrogateescape')

Thanks for your comment. I like your suggestion to consider using JSON to encode the message.

Also, in the original implementation there was a check that the message is not longer than 512 bytes, since writes shorter than PIPE_BUF (512 bytes on POSIX) are guaranteed to be atomic. But there was no check on the name length.

Now I check that the name is at most 255 bytes long, which is the value of NAME_MAX on Linux (including the leading slash that POSIX requires in shared memory and semaphore names).

I still encode the name using Base64, because json.dumps(..., ensure_ascii=True) would otherwise expand each non-ASCII byte into a 6-character escape like \uDC80. Using Base64 ensures that a 255-byte name becomes at most 340 bytes long, so the total JSON message always remains well below 512 bytes.

As a result, the previous runtime check for the message length is now replaced by an assert.

What do you think?

…the sent length below 512

encukou

Hm, good catch about still needing base64 for atomicity.
Hopefully, humans won't need to inspect the stream.

encukou · 2025-11-10T12:58:21Z

Lib/multiprocessing/resource_tracker.py

+                    line = raw.rstrip(b'\n')
+                    try:
+                        obj = json.loads(line.decode('ascii'))


Stripping and decoding shouldn't be needed; json.loads can handle bytes and trailing newlines.

encukou · 2025-11-10T12:59:29Z

Lib/multiprocessing/resource_tracker.py

+                    if not isinstance(cmd, str) or not isinstance(rtype, str) or not isinstance(b64, str):
+                        raise ValueError("malformed resource_tracker fields: %r" % (obj,))
+
+                    enc = b64.encode('ascii')


urlsafe_b64decode can handle bytes as well.

Lib/multiprocessing/resource_tracker.py

encukou · 2025-11-10T13:04:24Z

Lib/multiprocessing/resource_tracker.py

+                    cmd = obj.get("cmd")
+                    rtype = obj.get("rtype")
+                    b64  = obj.get("base64_name")


You don't need get with constant arguments:

Suggested change

cmd = obj.get("cmd")

rtype = obj.get("rtype")

b64 = obj.get("base64_name")

cmd = obj["cmd"]

rtype = obj["rtype"]

b64 = obj["base64_name"]

Alternately, make some fields optional -- then the PROBE message can be shorter:

Suggested change

cmd = obj.get("cmd")

rtype = obj.get("rtype")

b64 = obj.get("base64_name")

cmd = obj["cmd"]

rtype = obj["rtype"]

b64 = obj.get("base64_name", "")

bedevere-bot · 2025-11-11T12:45:15Z

🤖 New build scheduled with the buildbot fleet by @encukou for commit ea6416e 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F138473%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

encukou · 2025-11-12T12:41:01Z

Looks good! Thank you for the fix!

miss-islington-app · 2025-11-13T11:34:40Z

Thanks @rani-pinchuk for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

miss-islington-app · 2025-11-13T11:34:40Z

Thanks @rani-pinchuk for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

StanFromIreland · 2025-11-24T21:26:29Z

Lib/test/_test_multiprocessing.py

        res = assert_python_failure("-c", code, PYTHONWARNINGS='error')
        self.assertIn(b'DeprecationWarning', res.err)
        self.assertIn(b'is multi-threaded, use of forkpty() may lead to deadlocks in the child', res.err)
+


Suggested change

This should have been a double line gap. I'll fix it in the backports.

…itrary shared memory names (pythonGH-138473) (cherry picked from commit c6f3dd6) Co-authored-by: Rani Pinchuk <33353578+rani-pinchuk@users.noreply.github.com>

bedevere-app · 2025-11-24T21:28:13Z

GH-141922 is a backport of this pull request to the 3.14 branch.

… shared memory names (GH-138473) (GH-141922) Co-authored-by: Rani Pinchuk <33353578+rani-pinchuk@users.noreply.github.com>

…itrary shared memory names (pythonGH-138473) (pythonGH-141922) (cherry picked from commit 64d6bde38ffb97a6f7c7fee82ba98de81911f1b9) Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com> Co-authored-by: Rani Pinchuk <33353578+rani-pinchuk@users.noreply.github.com>

bedevere-app · 2025-11-27T12:22:13Z

GH-142014 is a backport of this pull request to the 3.13 branch.

… shared memory names (GH-138473) (GH-142014) (cherry picked from commit 64d6bde) Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com> Co-authored-by: Rani Pinchuk <33353578+rani-pinchuk@users.noreply.github.com>

rani-pinchuk requested a review from gpshead as a code owner September 3, 2025 19:41

bedevere-app bot added the awaiting review label Sep 3, 2025

bedevere-app bot mentioned this pull request Sep 3, 2025

Resource tracker fails to track filenames with colons on Linux #98896

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rani-pinchuk added 3 commits September 3, 2025 20:05

pythongh-98896: Fix parsing of registered or unregistered resources

ac9555d

Add test for shared memory names that contain colons

f3c8138

Fix the test

d973cf0

rani-pinchuk force-pushed the fix-shm-colon branch from 13ca553 to d973cf0 Compare September 3, 2025 20:13

📜🤖 Added by blurb_it.

e5f9549

encukou reviewed Nov 4, 2025

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Lib/multiprocessing/resource_tracker.py Outdated Show resolved Hide resolved

Address also newlines in shared_memory names by encoding and decoding…

9ac85d8

… the names

encukou reviewed Nov 6, 2025

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Sending the message as JSON and encode the name using base64 to keep …

84813da

…the sent length below 512

encukou reviewed Nov 10, 2025

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Fixes according to review comments

ea6416e

encukou added the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label Nov 11, 2025

bedevere-bot removed the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label Nov 11, 2025

encukou merged commit c6f3dd6 into python:main Nov 12, 2025
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bedevere-app bot removed the awaiting review label Nov 12, 2025

encukou added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Nov 13, 2025

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StanFromIreland removed needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Nov 24, 2025

StanFromIreland added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Nov 24, 2025

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StanFromIreland reviewed Nov 24, 2025

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bedevere-app bot removed the needs backport to 3.14 bugs and security fixes label Nov 24, 2025

encukou pushed a commit that referenced this pull request Nov 27, 2025

[3.14] gh-98896: resource_tracker: use json&base64 to allow arbitrary…

64d6bde

… shared memory names (GH-138473) (GH-141922) Co-authored-by: Rani Pinchuk <33353578+rani-pinchuk@users.noreply.github.com>

bedevere-app bot removed the needs backport to 3.13 bugs and security fixes label Nov 27, 2025

	name = base64.urlsafe_b64decode(enc_name.encode('ascii')).decode('utf-8', 'surrogateescape')
	name = base64.urlsafe_b64decode(enc_name).decode('utf-8', 'surrogateescape')

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gh-98896: Fix parsing issue in resource_tracker to allow shared memory names containing colons #138473

gh-98896: Fix parsing issue in resource_tracker to allow shared memory names containing colons #138473

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