fix: guard CFE_SB_GetUserDataLength against unsigned underflow#2754
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stark256-spec wants to merge 1 commit into
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fix: guard CFE_SB_GetUserDataLength against unsigned underflow#2754stark256-spec wants to merge 1 commit into
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When a SB message's CCSDS Length field encodes a total smaller than the secondary header size (e.g. Length=0 on a Cmd or Tlm message), the unsigned subtraction TotalMsgSize - HdrSize wraps to SIZE_MAX. Every downstream caller that uses this value as a buffer size or loop bound then performs an unbounded OOB read. Add a TotalMsgSize <= HdrSize guard that returns 0 for malformed messages, consistent with the existing NULL-pointer guard above. Fixes nasa/cFS#2697
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Looks like @linerfan5114's PR #2703 was opened for this issue before mine — I wasn't aware of it when I submitted #2754. Same root cause (unsigned underflow in @linerfan5114 — has #2703 merged, or is it still pending review? Happy to close #2754 as a duplicate either way, or if there's something my version handles differently that's useful, glad to fold it into yours instead. Just let me know. |
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Fixes #2697. When a SB message's CCSDS Length field encodes a total smaller than the header size, the unsigned subtraction
TotalMsgSize - HdrSizewraps to SIZE_MAX. Every downstream caller using this value as a buffer size or loop bound then performs an unbounded OOB read. Adds aTotalMsgSize <= HdrSizeguard returning 0 for malformed messages, consistent with the existing NULL-pointer guard.