Merge pull request #724 from bgd-labs/fix/100-rf

Fix indexes update with 100% reserve factor
aave · Nov 14, 2022 · cac49b4 · cac49b4
2 parents 02fbbd4 + 5d0a1aa
commit cac49b4
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Showing 2 changed files with 212 additions and 46 deletions.
diff --git a/contracts/protocol/libraries/logic/ReserveLogic.sol b/contracts/protocol/libraries/logic/ReserveLogic.sol
@@ -286,7 +286,9 @@ library ReserveLogic {
     reserveCache.nextLiquidityIndex = reserveCache.currLiquidityIndex;
     reserveCache.nextVariableBorrowIndex = reserveCache.currVariableBorrowIndex;
 
-    //only cumulating if there is any income being produced
+    // Only cumulating on the supply side if there is any income being produced
+    // The case of Reserve Factor 100% is not a problem (currentLiquidityRate == 0),
+    // as liquidity index should not be updated
     if (reserveCache.currLiquidityRate != 0) {
       uint256 cumulatedLiquidityInterest = MathUtils.calculateLinearInterest(
         reserveCache.currLiquidityRate,
@@ -296,19 +298,21 @@ library ReserveLogic {
         reserveCache.currLiquidityIndex
       );
       reserve.liquidityIndex = reserveCache.nextLiquidityIndex.toUint128();
+    }
 
-      //as the liquidity rate might come only from stable rate loans, we need to ensure
-      //that there is actual variable debt before accumulating
-      if (reserveCache.currScaledVariableDebt != 0) {
-        uint256 cumulatedVariableBorrowInterest = MathUtils.calculateCompoundedInterest(
-          reserveCache.currVariableBorrowRate,
-          reserveCache.reserveLastUpdateTimestamp
-        );
-        reserveCache.nextVariableBorrowIndex = cumulatedVariableBorrowInterest.rayMul(
-          reserveCache.currVariableBorrowIndex
-        );
-        reserve.variableBorrowIndex = reserveCache.nextVariableBorrowIndex.toUint128();
-      }
+    // Variable borrow index only gets updated if there is any variable debt.
+    // reserveCache.currVariableBorrowRate != 0 is not a correct validation,
+    // because a positive base variable rate can be stored on
+    // reserveCache.currVariableBorrowRate, but the index should not increase
+    if (reserveCache.currScaledVariableDebt != 0) {
+      uint256 cumulatedVariableBorrowInterest = MathUtils.calculateCompoundedInterest(
+        reserveCache.currVariableBorrowRate,
+        reserveCache.reserveLastUpdateTimestamp
+      );
+      reserveCache.nextVariableBorrowIndex = cumulatedVariableBorrowInterest.rayMul(
+        reserveCache.currVariableBorrowIndex
+      );
+      reserve.variableBorrowIndex = reserveCache.nextVariableBorrowIndex.toUint128();
     }
 
     //solium-disable-next-line
@@ -342,8 +346,10 @@ library ReserveLogic {
     reserveCache.reserveLastUpdateTimestamp = reserve.lastUpdateTimestamp;
 
     reserveCache.currScaledVariableDebt = reserveCache.nextScaledVariableDebt = IVariableDebtToken(
-      reserveCache.variableDebtTokenAddress
-    ).scaledTotalSupply();
+      reserveCache
+        .variableDebtTokenAddress
+    )
+      .scaledTotalSupply();
 
     (
       reserveCache.currPrincipalStableDebt,