gh-146266: Add bounds validation for _Py_DebugOffsets offset fields#146267
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jackhax wants to merge 1 commit intopython:mainfrom
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gh-146266: Add bounds validation for _Py_DebugOffsets offset fields#146267jackhax wants to merge 1 commit intopython:mainfrom
jackhax wants to merge 1 commit intopython:mainfrom
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…elds validate_debug_offsets() only checked the cookie and version but did not validate that individual offset fields are within their declared struct sizes. If a target process has corrupted _Py_DebugOffsets (e.g. from memory corruption or a misbehaving extension), the GET_MEMBER macro performs unchecked pointer arithmetic with the invalid offsets, causing RemoteUnwinder to crash with SIGSEGV. Add per-field bounds checking: each offset must be less than the .size of its containing sub-struct. Invalid offsets now raise RuntimeError with a descriptive message instead of crashing the debugger process. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Thanks for the PR @jackhax. Unfortunately I don't think this PR is the right way (see the comment in the issue). Feel free to continue the discussion there if we are missing anything. Thanks for you work! |
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Summary
validate_debug_offsets()now checks that every offset field in_Py_DebugOffsetsis within the declared.sizeof its containing sub-structRuntimeErrorwith a descriptive message instead of causing a SIGSEGV in the debugger processProblem
The
GET_MEMBERmacro in_remote_debugging.hperforms unchecked pointer arithmetic using offsets read from the target process. If those offsets are corrupted (memory corruption, partially-initialized interpreter, misbehaving extension),RemoteUnwinderdereferences a wild pointer and crashes with SIGSEGV.The existing
validate_debug_offsets()only checked the cookie and version — not the actual offset values.Fix
Added a
_CHECK_OFFSET(section, field)macro that verifiesoffset < sizefor each sub-struct's fields. This catches invalid offsets at attach time, before anyGET_MEMBERcalls.Test plan
test_remote_debuggingtests should pass unchanged (valid offsets always satisfy bounds checks)RuntimeErrorinstead of crashing the debugger