[PATCH 01/10] jump label: Add a WARN() if jump label key count goes negative

[Jason Baron]

The count on a jump label key should never go negative. Add a WARN() to
check for this condition.

Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Signed-off-by: Jason Baron <jbaron@xxxxxxxxxx>
---
 kernel/jump_label.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 01d3b70..ed9654f 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -76,8 +76,11 @@ EXPORT_SYMBOL_GPL(jump_label_inc);
 static void __jump_label_dec(struct jump_label_key *key,
 		unsigned long rate_limit, struct delayed_work *work)
 {
-	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
+	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
+		WARN(atomic_read(&key->enabled) < 0,
+		     "jump label: negative count!\n");
 		return;
+	}
 
 	if (rate_limit) {
 		atomic_inc(&key->enabled);
-- 
1.7.7.5

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