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cuckoocache: Check for uint32 overflow in setup_bytes

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This fixes an potential overflow which existed prior to this patchset.

If CuckooCache::cache<Element, Hash>::setup_bytes is called with a
`size_t bytes` which, when divided by sizeof(Element), does not fit into
an uint32_t, the implicit conversion to uint32_t in the call to setup
will result in an overflow.

At least on x86_64, this overflow is possible:

static_assert(std::numeric_limits<size_t>::max() / 32 <= std::numeric_limits<uint32_t>::max());
static_assert(std::numeric_limits<size_t>::max() / 4 <= std::numeric_limits<uint32_t>::max());

This commit detects such cases and signals to callers that the `size_t
bytes` input is too large.
This commit is contained in:
Carl Dong
2022-07-01 19:53:04 -04:00
parent b370164b31
commit 82d3058539
3 changed files with 15 additions and 5 deletions
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3
src/validation.cpp
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@@ -1669,8 +1669,9 @@ bool InitScriptExecutionCache() {
size_t nMaxCacheSize = std::max((int64_t)0, gArgs.GetIntArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 2) * ((size_t) 1 << 20);
auto setup_results = g_scriptExecutionCache.setup_bytes(nMaxCacheSize);
if (!setup_results) return false;
const auto [num_elems, approx_size_bytes] = setup_results;
const auto [num_elems, approx_size_bytes] = *setup_results;
LogPrintf("Using %zu MiB out of %zu/2 requested for script execution cache, able to store %zu elements\n",
approx_size_bytes >> 20, (nMaxCacheSize * 2) >> 20, num_elems);
return true;