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Fix address bounds check in get_reg_block #2926

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Merged
janiversen merged 1 commit into from
Apr 23, 2026
+9 −1
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Fix address bounds check in get_reg_block #2926

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2 changes: 1 addition & 1 deletion pymodbus/simulator/simruntime.py
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,7 @@ async def get_reg_block(self, block_id: str, func_code: int, address: int, count
"""Handle holding registers and input registers."""
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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@janiversen janiversen Apr 23, 2026

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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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@foolip foolip Apr 23, 2026

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Did you mean to merge this without any further changes?

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@janiversen janiversen Apr 23, 2026

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yes, the PR solved the problem which is enough.

return ExcCodes.ILLEGAL_ADDRESS
if (result := await self.__check_block(func_code, block_id, address, count, offset, values)):
return result
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8 changes: 8 additions & 0 deletions test/simulator/test_simruntime.py
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Expand Up @@ -135,6 +135,14 @@ async def test_simruntime_getValues(self):
rt = SimRuntime(sd)
result = await rt.async_getValues(0x03, 10, 1)
assert result == [15]
result = await rt.async_getValues(0x03, 8, 1)
assert isinstance(result, ExcCodes)
result = await rt.async_getValues(0x03, 9, 1)
assert isinstance(result, ExcCodes)
result = await rt.async_getValues(0x03, 11, 1)
assert isinstance(result, ExcCodes)
result = await rt.async_getValues(0x03, 12, 1)
assert isinstance(result, ExcCodes)
result = await rt.async_getValues(0x03, 15, 1)
assert isinstance(result, ExcCodes)

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