fix(vm): fix "safe" conversions from Uint<256> to usize (#546)

crates/vm/src/core/vm.rs

@@ -832,14 +832,13 @@ impl VM {
                 let offset = self.stack.pop()?.value;
                 let size = self.stack.pop()?.value;
 
-                // Safely convert U256 to usize
-                // Note: clamping to 8 words here, since we dont actually use the return data
-                let dest_offset: usize = dest_offset.try_into()?;
-                let offset: usize = offset.try_into()?;
-                let size: usize = size.try_into()?;
+                // Safely convert U256 to usize, clamping to calldata length
+                let dest_offset: usize = dest_offset.try_into().unwrap_or(usize::MAX);
+                let offset: usize = offset.try_into().unwrap_or(usize::MAX);
+                let size: usize = size.try_into().unwrap_or(usize::MAX);
 
                 // clamp values to calldata length
-                let end_offset_clamped = (offset + size).min(self.calldata.len());
+                let end_offset_clamped = offset.saturating_add(size).min(self.calldata.len());
                 let size = size.min(self.calldata.len());
 
                 let mut value =
@@ -877,13 +876,12 @@ impl VM {
                 let offset = self.stack.pop()?.value;
                 let size = self.stack.pop()?.value;
 
-                // Safely convert U256 to usize
-                // Note: clamping to 8 words here, since we dont actually use the return data
-                let dest_offset: usize = dest_offset.try_into()?;
-                let offset: usize = offset.try_into()?;
-                let size: usize = size.try_into()?;
+                // Safely convert U256 to usize, clamping to bytecode length
+                let dest_offset: usize = dest_offset.try_into().unwrap_or(usize::MAX);
+                let offset: usize = offset.try_into().unwrap_or(usize::MAX);
+                let size: usize = size.try_into().unwrap_or(usize::MAX);
 
-                let value_offset_safe = (offset + size).min(self.bytecode.len());
+                let value_offset_safe = offset.saturating_add(size).min(self.bytecode.len());
                 let mut value =
                     self.bytecode.get(offset..value_offset_safe).unwrap_or(&[]).to_owned();
 
@@ -934,7 +932,6 @@ impl VM {
                 let size = self.stack.pop()?.value;
 
                 // Safely convert U256 to usize
-                // Note: clamping to 8 words here, since we dont actually use the return data
                 let dest_offset: usize = dest_offset.try_into()?;
                 let size: usize = size.try_into()?;
 
@@ -974,7 +971,6 @@ impl VM {
                 let size = self.stack.pop()?.value;
 
                 // Safely convert U256 to usize
-                // Note: clamping to 8 words here, since we dont actually use the return data
                 let dest_offset: usize = dest_offset.try_into()?;
                 let size: usize = size.try_into()?;
 
@@ -1118,7 +1114,7 @@ impl VM {
                 let pc = self.stack.pop()?.value;
 
                 // Safely convert U256 to u128
-                let pc: u128 = pc.try_into()?;
+                let pc: u128 = pc.try_into().unwrap_or(u128::MAX);
 
                 // Check if JUMPDEST is valid and throw with 790 if not (invalid jump destination)
                 if (pc <=
@@ -1148,7 +1144,7 @@ impl VM {
                 let condition = self.stack.pop()?.value;
 
                 // Safely convert U256 to u128
-                let pc: u128 = pc.try_into()?;
+                let pc: u128 = pc.try_into().unwrap_or(u128::MAX);
 
                 if !condition.eq(&U256::from(0u8)) {
                     // Check if JUMPDEST is valid and throw with 790 if not (invalid jump
@@ -1197,12 +1193,12 @@ impl VM {
                 let offset = self.stack.pop()?.value;
                 let size = self.stack.pop()?.value;
 
-                // Safely convert U256 to usize
-                // Note: clamping to 8 words here, since we dont actually use the return data
-                let dest_offset: usize = dest_offset.try_into()?;
-                let offset: usize = offset.try_into()?;
-                let size: usize = size.try_into()?;
-                let value_offset_safe = (offset + size)
+                // Safely convert U256 to usize, clamping to memory length
+                let dest_offset: usize = dest_offset.try_into().unwrap_or(u128::MAX as usize);
+                let offset: usize = offset.try_into().unwrap_or(u128::MAX as usize);
+                let size: usize = size.try_into().unwrap_or(u128::MAX as usize);
+                let value_offset_safe = offset
+                    .saturating_add(size)
                     .min(self.memory.size().try_into().expect("failed to convert u128 to usize"));
 
                 let mut value =