TX fees and policy: fix relaypriority calculation error Issues #8334 #8336

CCoinsViewCache::GetPriority has an overflow bug that affects the relaypriority calculation. The way the arithmetic works in that function is

dResult += coins->vout[txin.prevout.n].nValue * (nHeight-coins->nHeight); 
the nValue variable type is int64_t, and the int64_t max value is 9223372036854775807

for example

nValue value  is 40000000000000
(nHeight->coins - nHeight )value is 300000 
40000000000000 * 300000 > 9223372036854775807 

so the dResult will be negative number! and the AllowFree function will return False, and the high priority transaction with low fee will be reject by node with error insufficient priority!

Mind to amend the commit subject to be more verbose?

utACK e290b2ab0055405099f5a4899b9f7aa506a2648d. I think a short unit or RPC test would be nice.

I think that in this case, it is also worth to mention the reason to cast the value to double in the source code!

I think that in this case, it is also worth to mention the reason to cast the value to double in the source code!

Should be enough to mention it in the commit subject line, so when in doubt, you can always do git blame.

@maiiz You can change the commit subject line with git commit --amend, if you didn't know. Make sure to force push afterward.