From e0655e24f2635011e055758c2ec4f348bb8b3347 Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Wed, 28 Oct 2020 19:24:01 -0700
Subject: [PATCH] fix: A possible crash when fi.Erasure.Distribution is empty
 (#10779)

---
 cmd/erasure-healing-common.go | 17 +++++++++++++++++
 cmd/erasure-metadata.go       |  5 ++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/cmd/erasure-healing-common.go b/cmd/erasure-healing-common.go
index 2615e3599..8806646a1 100644
--- a/cmd/erasure-healing-common.go
+++ b/cmd/erasure-healing-common.go
@@ -167,7 +167,14 @@ func disksWithAllParts(ctx context.Context, onlineDisks []StorageAPI, partsMetad
 			// consider the offline disks as consistent.
 			continue
 		}
+		if len(meta.Erasure.Distribution) != len(onlineDisks) {
+			// Erasure distribution seems to have lesser
+			// number of items than number of online disks.
+			inconsistent++
+			continue
+		}
 		if meta.Erasure.Distribution[i] != meta.Erasure.Index {
+			// Mismatch indexes with distribution order
 			inconsistent++
 		}
 	}
@@ -193,6 +200,16 @@ func disksWithAllParts(ctx context.Context, onlineDisks []StorageAPI, partsMetad
 			if !meta.IsValid() {
 				continue
 			}
+
+			if len(meta.Erasure.Distribution) != len(onlineDisks) {
+				// Erasure distribution is not the same as onlineDisks
+				// attempt a fix if possible, assuming other entries
+				// might have the right erasure distribution.
+				partsMetadata[i] = FileInfo{}
+				dataErrs[i] = errFileCorrupt
+				continue
+			}
+
 			// Since erasure.Distribution is trustable we can fix the mismatching erasure.Index
 			if meta.Erasure.Distribution[i] != meta.Erasure.Index {
 				partsMetadata[i] = FileInfo{}
diff --git a/cmd/erasure-metadata.go b/cmd/erasure-metadata.go
index b1c595d04..386852b16 100644
--- a/cmd/erasure-metadata.go
+++ b/cmd/erasure-metadata.go
@@ -90,9 +90,12 @@ func (fi FileInfo) IsValid() bool {
 	}
 	dataBlocks := fi.Erasure.DataBlocks
 	parityBlocks := fi.Erasure.ParityBlocks
+	correctIndexes := (fi.Erasure.Index > 0 &&
+		fi.Erasure.Index <= dataBlocks+parityBlocks &&
+		len(fi.Erasure.Distribution) == (dataBlocks+parityBlocks))
 	return ((dataBlocks >= parityBlocks) &&
 		(dataBlocks != 0) && (parityBlocks != 0) &&
-		(fi.Erasure.Index > 0 && fi.Erasure.Distribution != nil))
+		correctIndexes)
 }
 
 // ToObjectInfo - Converts metadata to object info.