Fix setting bounds (non-canonical) untagged capabilities #11
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jrtc27
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Jan 11, 2023
arichardson
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jrtc27
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Jan 12, 2023
jrtc27
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Rebased and fixed issues. |
…ties When called on untagged quantities these do not necessarily hold.
…ility This was found by the fuzzer since it triggered an assertion, now it matches the sail outputs. When calling decompress_raw we have to use req_base and not the current address to infer the bounds. This did not matter previously since we only called the function on in-bounds caps, so the result was the same, but now that we allow out-of-bounds untagged values, we have to use req_base instead and set the address to req_base.
Due to the way we decode top/bot it is possible for top to decode to 1<<66, but that is then truncated to zero and can therefore be less than the base of the capability. The example test case was found by TestRIG See CTSRD-CHERI/sail-cheri-riscv#36 for an alternative decoding approach that guarantees top >= base.
arichardson
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Found another assertion that can be triggered on untagged inputs. Relaxing this also seems fine unless we decide to merge CTSRD-CHERI/sail-cheri-riscv#36. |
Actually request more than 2 addresses worth of input, so we end up with a non-zero req_len input. With this change the assertion relaxed in the last commit is also found by libfuzzer.
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If there are no further comments I will merge this tomorrow. |
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This was found by the fuzzer since it triggered an assertion, now it
matches the sail outputs.
When calling decompress_raw we have to use req_base and not the current
address to infer the bounds. This did not matter previously since we only
called the function on in-bounds caps, so the result was the same, but now
that we allow out-of-bounds untagged values, we have to use req_base
instead and set the address to req_base.