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fbpt: reject undersized record lengths before subtraction#3643
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Signed-off-by: alhudz <al.hudz.k@gmail.com>
Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #3643 +/- ##
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+ Coverage 60.86% 60.89% +0.02%
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Files 659 659
Lines 46494 46500 +6
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+ Hits 28299 28314 +15
+ Misses 18195 18186 -9
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Repro:feed an FBPT whose dynamic-string record declares aLengthbelow 34 (the 4-byte record header plus the 30 fixed bytes); seepkg/acpi/fpdt/fbpt/fbpt_test.go.Expected:the parser rejects the short record.Actual:recordLength-34underflows theuint8, somake([]byte, recordLength-34)sizes up to 255 bytes andio.ReadFullcopies that much adjacent memory intoDescription. The same unsigned-underflow shape sits inFindAllFBPTRecords:tablelength-8(uint32) in the loop bound andHeaderInfo.Length-4(uint8) before the skipSeek, both fed straight from the firmware table.Fix:check each length is at least the fixed size it is about to have subtracted, returning an error otherwise.Verified the
recordLength<34case reads 252 bytes of trailing data intoDescriptionbefore the patch and errors after.