Author

Hood Chatham <roberthoodchatham@gmail.com> 2025-10-17 20:22:23 -0700

Parents

c3d0dd0

Tree

cedc294

Python snapshots: Fix path confusion when preloading dynamic libraries (#5335)

There was a bug where we confused the site-packages directory with the
/usr/lib directory for the sake of resolving dynamic library paths.
This causes us to preload libcrypto.so under the incorrect path
/session/lib/python3.13/site-packages/libcrypto.so instead of
/usr/lib/libcrypto.so where it belongs. As a result of this, if we import
any new packages (for example hashlib) that depend on libcrypto, the loader
won't find it and will load it a second time. This works alright except that
if we make a stacked memory snapshot, when we do the preloading we'll confuse
both paths into /session/lib/python3.13/site-packages/libcrypto.so and the
second load will be dropped. This causes an incorrect offset in the table base
and so the loader will relocate all shared libraries loaded after haslib
incorrectly.

The bug was introduced here:
https://github.com/cloudflare/workerd/pull/4612/files#diff-510242e139d24007d0356f32dbf4dfb6395b35498b5106813bb5bc6c9edd6030R295-R307
but only became noticeable when we started using dedicated snapshots.