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Set mmap_rnd_bits to 28 in TSAN build - #292

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hugovk merged 1 commit into
python-pillow:mainfrom
radarhere:tsan
Oct 28, 2026
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hugovk merged 1 commit into
python-pillow:mainfrom
radarhere:tsan

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@radarhere

@radarhere radarhere commented Oct 28, 2026 •

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After automatically updating to Ubuntu 26.04, the TSAN build is currently failing in main - https://github.com/python-pillow/docker-images/actions/runs/40696047113/job/122842970176

0.273 FATAL: ThreadSanitizer: encountered an incompatible memory layout but was unable to disable ASLR (perhaps sandboxing is enabled?).
0.273 FATAL: Please rerun with lower ASLR entropy, ASLR disabled, and/or sandboxing disabled.

https://en.wikipedia.org/wiki/Address_space_layout_randomization

A number of sysctl options control the behavior of mainline ASLR... vm.mmap_rnd_bits controls how many bits to randomize for mmap.

Setting mmap_rnd_bits to the value that it had on Ubuntu 24.04 fixes it.

@hugovk
hugovk merged commit e5c0a93 into python-pillow:main Oct 28, 2026
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@radarhere
radarhere deleted the tsan branch October 28, 2026 23:44
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