vfs: Check that open() resulted in a file-like object. #17868
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That is, an object whose type defines the protocol slot. Note that due to protocol confusion, a variant of the original crasher that returned e.g., a machine.Pin instance could still lead to a crash. (micropython#17852) Closes: micropython#17841 Signed-off-by: Jeff Epler <jepler@gmail.com>
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Multiple tests fail because their vfs open method returns None (or other unsuitable objects, I didn't look any further than the first one). Should the tests be corrected so they return a minimal file-like object, or should I take a different approach to resolving the crash in |
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Summary
Check that open() results in a file-like object, preventing crashes in callers to
mp_vfs_openwhen an object that is "not actually a file" is returned. This includes, for example,execfile.Closes: #17841
Testing
I added a test derived from the reproducer in #17841.
Trade-offs and Alternatives
The code can only ensure that the object's type defines a protocol slot. Due to protocol confusion, a variant of the original crasher that returned e.g., a machine.Pin instance could still lead to a crash. (#17852)