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GeezerVison is showing github.com — gh-134070: Prevent out-of-bounds read in mi_clz32 and mi_ctz32 by vedant713 · Pull Request #134149 · python/cpython

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@vedant713

@vedant713 vedant713 commented May 17, 2025

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Fixes GH-134070

Summary:
This patch adds a masking operation to the index calculation in mi_ctz32() and mi_clz32() functions to prevent out-of-bounds access on 64-bit systems, matching the fix from upstream mimalloc.

Why:
On systems where unsigned long is 64-bit, the multiplication may produce a value >31, causing a read outside the array bounds.

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@vedant713
Fix: Prevent out-of-bounds read in mi_clz32 and mi_ctz32 (python#134070)
e8466b0
@bedevere-app

bedevere-app Bot commented May 17, 2025

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.
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@bedevere-app bedevere-app Bot added the awaiting review label May 17, 2025
@ZeroIntensity ZeroIntensity changed the title Fix: Prevent out-of-bounds read in mi_clz32 and mi_ctz32 (#134070) gh-134070: Prevent out-of-bounds read in mi_clz32 and mi_ctz32 (#134070) May 17, 2025
@ZeroIntensity
ZeroIntensity requested a review from colesbury May 17, 2025 18:51
@bedevere-app bedevere-app Bot mentioned this pull request May 17, 2025
Out-of-bounds read in integrated mimalloc (fixed upstream) #134070
Closed
@ZeroIntensity ZeroIntensity added needs backport to 3.13 only security fixes needs backport to 3.14 bugs and security fixes labels May 17, 2025
@ZeroIntensity ZeroIntensity changed the title gh-134070: Prevent out-of-bounds read in mi_clz32 and mi_ctz32 (#134070) gh-134070: Prevent out-of-bounds read in mi_clz32 and mi_ctz32 May 17, 2025
ZeroIntensity
ZeroIntensity reviewed May 17, 2025
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Please add a test and blurb.

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@collinfunk

collinfunk commented May 17, 2025

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FYI, this code is from https://github.com/microsoft/mimalloc. You might want to send a pull request there too.
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@picnixz

picnixz commented May 17, 2025

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It's said to be fixed in microsoft/mimalloc@ed31847.
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vedant713 added a commit to vedant713/cpython that referenced this pull request May 17, 2025
@vedant713
pythongh-134070: Fix mi_clz32/mi_ctz32 to prevent out-of-bounds read (p…
960e266 
…ythonGH-134149)
@vedant713
Merge branch 'main' into fix-mimalloc-bug
3658bc3
@bedevere-app

bedevere-app Bot commented May 17, 2025

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.
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@picnixz

picnixz commented May 17, 2025

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Please, stop updating two PRs at the same time. See https://devguide.python.org/getting-started/pull-request-lifecycle/. I am going to close the other PR as it only contains the NEWS entry. In addition, please do not merge main into this branch if there is no conflict. TiA.
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@picnixz picnixz mentioned this pull request May 17, 2025
gh-134070: Fix mi_clz32/mi_ctz32 to prevent out-of-bounds read (GH-134149) #134157
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@vedant713

vedant713 commented May 17, 2025

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I'm trying to add via heroku app but giving server error
bedevere/news
bedevere/news — No news entry in Misc/NEWS.d/next/ or "skip news" label found
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@picnixz

picnixz commented May 17, 2025 •
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I never used the app, so I'd suggest using the command-line instead:

python -m pip install blurb
python -m blurb
git commit -m 'blurb'
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@picnixz
picnixz marked this pull request as draft May 17, 2025 20:33
@bedevere-app bedevere-app Bot removed the awaiting review label May 17, 2025
vedant713 added 4 commits May 17, 2025 17:15
@vedant713
pythongh-134070: Add news entry for mimalloc out-of-bounds fix
64e9718
@vedant713
pythongh-134070: Add news entry for mimalloc out-of-bounds fix
c961fa0
@vedant713
pythongh-134070: Add news entry for mimalloc out-of-bounds fix
911c128
@vedant713
pythongh-134070: Add news entry for mimalloc out-of-bounds fix
bce07b2
@vedant713
vedant713 marked this pull request as ready for review May 17, 2025 21:52
@bedevere-app bedevere-app Bot added the awaiting review label May 17, 2025
@collinfunk

collinfunk commented May 17, 2025

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@picnixz Thanks for checking. Somehow I missed that commit in mimalloc.
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@colesbury

colesbury commented May 18, 2025

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I think we should copy-paste the change from upstream instead of doing a similar (but not identical) fix here.

In other words, copy this code from upstream (from the fix commit) into our mimalloc/internal.h file.

https://github.com/microsoft/mimalloc/blob/ed318471126918fce7caf0001cf1e0c78f95173e/include/mimalloc/internal.h#L875-L932
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@picnixz

picnixz commented Jul 12, 2025

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@vedant713 Are you still working on this one?
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vedant713 added 2 commits July 13, 2025 19:33
@vedant713
Update internal.h
bd186c9
@vedant713
Update internal.h
796a176
@github-actions

github-actions Bot commented Apr 24, 2026

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This PR is stale because it has been open for 30 days with no activity.
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@github-actions github-actions Bot added the stale Stale PR or inactive for long period of time. label Apr 24, 2026
@serhiy-storchaka serhiy-storchaka added the needs backport to 3.15 bugs and security fixes label May 30, 2026
@github-actions github-actions Bot removed the stale Stale PR or inactive for long period of time. label May 31, 2026
@github-actions

github-actions Bot commented Sep 3, 2026

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This PR is stale because it has been open for 90 days with no activity.
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@github-actions github-actions Bot added the stale Stale PR or inactive for long period of time. label Sep 3, 2026
@corona10 corona10 closed this Nov 2, 2026
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Out-of-bounds read in integrated mimalloc (fixed upstream)

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@vedant713 @collinfunk @picnixz @colesbury @ZeroIntensity @serhiy-storchaka @corona10
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