Fix address bounds check in get_reg_block#2926
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janiversen merged 1 commit intopymodbus-dev:devfrom Apr 23, 2026
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Because offset can be negative, register_count <= offset < 0 doesn't work. It's specifically `rt.async_getValues(0x03, 8, 1)` that would previously incorrectly pass the bounds check and return a value (15) due to negative list indexing. Going even further out of bounds would instead throw an IndexError. Discovered while SimDevice/SimData for a simple static test server.
janiversen
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Apr 23, 2026
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Good catch, but needs some small changes.
| start_address, register_count, registers, _ = self.block[block_id] | ||
| offset = address - start_address | ||
| if register_count <= offset < 0 or offset + count > register_count: | ||
| if offset < 0 or offset + count > register_count: |
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This seems to be the wrong fix, it would be more logical to test that address >= start_address.
This should also be done in set_values
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Did you mean to merge this without any further changes?
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yes, the PR solved the problem which is enough.
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Apr 23, 2026
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Because offset can be negative, register_count <= offset < 0 doesn't work.
It's specifically
rt.async_getValues(0x03, 8, 1)that would previouslyincorrectly pass the bounds check and return a value (15) due to negative list
indexing. Going even further out of bounds would instead throw an IndexError.
Discovered while SimDevice/SimData for a simple static test server.