From b956e8ef35ff30ff771bfe1d38008438ffd027f0 Mon Sep 17 00:00:00 2001
From: Pierre Carles <51314945+pcarles@users.noreply.github.com>
Date: Wed, 12 Feb 2020 16:10:52 +0100
Subject: [PATCH] Fix negative parallelism and negative semaphore (#23902)

* Throw an error when parallelism <=0

* Panic in case of negative semaphore
---
 terraform/context.go | 10 ++++++++++
 terraform/util.go    |  4 ++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/terraform/context.go b/terraform/context.go
index 5637083ce0..2a438787f0 100644
--- a/terraform/context.go
+++ b/terraform/context.go
@@ -138,7 +138,17 @@ func NewContext(opts *ContextOpts) (*Context, tfdiags.Diagnostics) {
 	// Determine parallelism, default to 10. We do this both to limit
 	// CPU pressure but also to have an extra guard against rate throttling
 	// from providers.
+	// We throw an error in case of negative parallelism
 	par := opts.Parallelism
+	if par < 0 {
+		diags = diags.Append(tfdiags.Sourceless(
+			tfdiags.Error,
+			"Invalid parallelism value",
+			fmt.Sprintf("The parallelism must be a positive value. Not %d.", par),
+		))
+		return nil, diags
+	}
+
 	if par == 0 {
 		par = 10
 	}
diff --git a/terraform/util.go b/terraform/util.go
index 5428cd5a0a..7966b58dd2 100644
--- a/terraform/util.go
+++ b/terraform/util.go
@@ -12,8 +12,8 @@ type Semaphore chan struct{}
 // NewSemaphore creates a semaphore that allows up
 // to a given limit of simultaneous acquisitions
 func NewSemaphore(n int) Semaphore {
-	if n == 0 {
-		panic("semaphore with limit 0")
+	if n <= 0 {
+		panic("semaphore with limit <=0")
 	}
 	ch := make(chan struct{}, n)
 	return Semaphore(ch)