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chaintopology: Protect against underflow when computing first_blocknum.

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Fixes: #1423

(Hopefully)

Reported-by: @NicolasDorier
This commit is contained in:
ZmnSCPxj 2018-04-26 05:21:45 +00:00 committed by Rusty Russell
parent aa71a822b3
commit d5a67ec87a
1 changed files with 12 additions and 2 deletions
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14
lightningd/chaintopology.c
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@ -525,10 +525,20 @@ static void get_init_blockhash(struct bitcoind *bitcoind, u32 blockcount,
if (blockcount < topo->first_blocknum) {
if (bitcoind->ld->config.rescan < 0) {
/* Absolute blockheight, but bitcoind's blockheight isn't there yet */
topo->first_blocknum = blockcount - 1;
/* Protect against underflow in subtraction.
* Possible in regtest mode. */
if (blockcount < 1)
topo->first_blocknum = 0;
else
topo->first_blocknum = blockcount - 1;
} else if (topo->first_blocknum == UINT32_MAX) {
/* Relative rescan, but we didn't know the blockheight */
topo->first_blocknum = blockcount - bitcoind->ld->config.rescan;
/* Protect against underflow in subtraction.
* Possible in regtest mode. */
if (blockcount < bitcoind->ld->config.rescan)
topo->first_blocknum = 0;
else
topo->first_blocknum = blockcount - bitcoind->ld->config.rescan;
}
}