From c0ec3772698fd7eed226e273a46386bc2b2d8308 Mon Sep 17 00:00:00 2001
From: Tommi Virtanen <tv@eagain.net>
Date: Sun, 31 May 2015 15:47:36 -0700
Subject: [PATCH] pin: Guard against callers causing refcount underflow

This used to lead to large refcount numbers, causing Flush to create a
lot of IPFS objects, and merkledag to consume tens of gigabytes of
RAM.

License: MIT
Signed-off-by: Jeromy <jeromyj@gmail.com>
---
 pin/indirect.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pin/indirect.go b/pin/indirect.go
index dca99600f..e5ed5dcb6 100644
--- a/pin/indirect.go
+++ b/pin/indirect.go
@@ -57,6 +57,10 @@ func (i *indirectPin) Increment(k key.Key) {
 }
 
 func (i *indirectPin) Decrement(k key.Key) {
+	if i.refCounts[k] == 0 {
+		log.Warningf("pinning: bad call: asked to unpin nonexistent indirect key: %v", k)
+		return
+	}
 	c := i.refCounts[k] - 1
 	i.refCounts[k] = c
 	if c <= 0 {