exrcheck: use 64 bit integer math to prevent pointer overflows #930
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Signed-off-by: Peter Hillman <peterh@wetafx.co.nz>
meshula
reviewed
Feb 22, 2021
src/lib/OpenEXRUtil/ImfCheckFile.cpp
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| @@ -521,9 +529,14 @@ readDeepTile(T& in,bool reduceMemory , bool reduceTime) | |||
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| DeepFrameBuffer frameBuffer; | |||
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| int memOffset = dataWindow.min.x + dataWindow.min.y * width; | |||
| // | |||
| // use 64 bit integer arithmetic instead of pointer arithmetic to compute offset into array. Pointer arithmetic may overflow | |||
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I suggest amending the comment to 'pointer arithmetic may overflow on 32 bit architectures'
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I have amended accordingly. I think this is architecture dependent, and more to do with the size of ints.
The value of 'memOffset' needs to be computed with 64 bit arithmetic. For example, if dataWindow.min.y*width is greater than 2^31 and dataWindow.min.x is very negative, the end result should be a relatively small number.
Also, I think memOffset needs to be 64 bits on a 64 bit architecture.
meshula
reviewed
Feb 22, 2021
Signed-off-by: Peter Hillman <peterh@wetafx.co.nz>
meshula
approved these changes
Feb 22, 2021
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Address issues:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=31221
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=31228
(also, all example images read through
exrcheckwhen compiled with the undefined behavior sanitizer)exrcheck had the usual thorny bugs handling images with massively offset data windows. Where dataWindow.min.{x,y} are very large or very negative, 32 bit integer arithmetic overflows and/or negative pointer arithmetic occurred.
Signed-off-by: Peter Hillman peterh@wetafx.co.nz