fix(imagebuf): fix data race that could corrupt multithreaded reads - #5325
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The Mac CI failures are unrelated to this PR -- looks like GHA Mac runners updated their OpenCV and it's not compatible with what we're looking for. |
m_pixels_valid was set true by realloc() as soon as the pixel buffer was allocated, before read() actually filled it with file data. Since validate_pixels() checks the flag lock-free before falling back to the mutex, a second thread (e.g. another computePixelHashSHA1 block) could see it as true and read a still-empty buffer. init_spec() had the same issue with m_spec_valid, set before all spec fields were written. Move both flags to be set only after their data is fully populated, and make them (plus m_pixels_read, read via the public ImageBuf::pixels_read() with no lock) atomic so their lock-free readers get a proper memory barrier. Assisted-by: Claude Code / Sonnet 5 Signed-off-by: Larry Gritz <lg@larrygritz.com>
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No objections -> merging |
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…cademySoftwareFoundation#5325) m_pixels_valid was set true by realloc() as soon as the pixel buffer was allocated, before read() actually filled it with file data. Since validate_pixels() checks the flag lock-free before falling back to the mutex, a second thread (e.g. another computePixelHashSHA1 block) could see it as true and read a still-empty buffer. init_spec() had the same issue with m_spec_valid, set before all spec fields were written. Move both flags to be set only after their data is fully populated, and make them (plus m_pixels_read, read via the public ImageBuf::pixels_read() with no lock) atomic so their lock-free readers get a proper memory barrier. Fixes AcademySoftwareFoundation#5324 Assisted-by: Claude Code / Sonnet 5 Signed-off-by: Larry Gritz <lg@larrygritz.com>
lgritz
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…cademySoftwareFoundation#5325) m_pixels_valid was set true by realloc() as soon as the pixel buffer was allocated, before read() actually filled it with file data. Since validate_pixels() checks the flag lock-free before falling back to the mutex, a second thread (e.g. another computePixelHashSHA1 block) could see it as true and read a still-empty buffer. init_spec() had the same issue with m_spec_valid, set before all spec fields were written. Move both flags to be set only after their data is fully populated, and make them (plus m_pixels_read, read via the public ImageBuf::pixels_read() with no lock) atomic so their lock-free readers get a proper memory barrier. Fixes AcademySoftwareFoundation#5324 Assisted-by: Claude Code / Sonnet 5 Signed-off-by: Larry Gritz <lg@larrygritz.com>
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m_pixels_valid was set true by realloc() as soon as the pixel buffer was allocated, before read() actually filled it with file data. Since validate_pixels() checks the flag lock-free before falling back to the mutex, a second thread (e.g. another computePixelHashSHA1 block) could see it as true and read a still-empty buffer. init_spec() had the same issue with m_spec_valid, set before all spec fields were written.
Move both flags to be set only after their data is fully populated, and make them (plus m_pixels_read, read via the public ImageBuf::pixels_read() with no lock) atomic so their lock-free readers get a proper memory barrier.
Fixes #5324
Assisted-by: Claude Code / Sonnet 5