From 6ea602996e90182b4842acb1f71da1fa81a9d00d Mon Sep 17 00:00:00 2001
From: Xiliang Chen <xlchen1291@gmail.com>
Date: Thu, 1 Oct 2020 16:27:43 +1300
Subject: [PATCH] ensure .abs() can't overflow (#298)

---
 tokens/src/lib.rs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tokens/src/lib.rs b/tokens/src/lib.rs
index a7ddbfb5b..861b4c3cd 100644
--- a/tokens/src/lib.rs
+++ b/tokens/src/lib.rs
@@ -474,8 +474,16 @@ impl<T: Trait> MultiCurrencyExtended<T::AccountId> for Module<T> {
 			return Ok(());
 		}
 
+		// Ensure this doesn't overflow. There isn't any traits that exposes
+		// `saturating_abs` so we need to do it manually.
+		let by_amount_abs = if by_amount == Self::Amount::min_value() {
+			Self::Amount::max_value()
+		} else {
+			by_amount.abs()
+		};
+
 		let by_balance =
-			TryInto::<Self::Balance>::try_into(by_amount.abs()).map_err(|_| Error::<T>::AmountIntoBalanceFailed)?;
+			TryInto::<Self::Balance>::try_into(by_amount_abs).map_err(|_| Error::<T>::AmountIntoBalanceFailed)?;
 		if by_amount.is_positive() {
 			Self::deposit(currency_id, who, by_balance)
 		} else {