Merge pull request #445 from ethereum/fix-mem-out

Fixing out-of-heap error due to large memory copy

CHANGELOG.md

@@ -9,6 +9,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Minimum distance requirements are now asserted for Keccak function calls. They assert that it's hard to generate two Keccak's that are less than 256 afar.
 - Keccak concretization is now done only after all simplifications are performed. This helps with simplification pre-concretization
+- Added an IllegalOverflow error in case the system tries to allocate a large amount of memory during
+  abstract gas execution but concrete running. In these cases, the interpreter can out-of-heap
+  as the only check is that the size allocated is less than $2**{64}$, but that is too large to fit in memory. Now,
+  we check more stringently, and still return an IllegalOverflow
 
 ## Added
 

src/EVM.hs

@@ -2085,7 +2085,13 @@ accessMemoryRange (Lit offs) (Lit sz) continue =
     Just (offs64, sz64) ->
       if offs64 + sz64 < sz64
         then vmError IllegalOverflow
-        else accessUnboundedMemoryRange offs64 sz64 continue
+        -- we need to limit these to <256MB because otherwise we could run out of memory
+        -- in e.g. OpCalldatacopy and subsequent memory allocation when running with abstract gas.
+        -- In these cases, the system would try to allocate a large (but <2**64 bytes) memory
+        -- that leads to out-of-heap. Real-world scenarios cannot allocate 256MB of memory due to gas
+        else if offs64 >= 0x0fffffff || sz64 >= 0x0fffffff
+             then vmError IllegalOverflow
+             else accessUnboundedMemoryRange offs64 sz64 continue
 -- we just ignore gas if we get symbolic inputs
 accessMemoryRange _ _ continue = continue