linux-kernel - [PATCH] Don't risk NULL deref in marker

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Message-Id: <200802260014.24253.jesper.juhl@gmail.com>
Date:	Tue, 26 Feb 2008 00:14:24 +0100
From:	Jesper Juhl <jesper.juhl@...il.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Jesper Juhl <jesper.juhl@...il.com>
Subject: [PATCH] Don't risk NULL deref in marker


get_marker() may return NULL, so test for it.


Signed-off-by: Jesper Juhl <jesper.juhl@...il.com>
---

diff --git a/kernel/marker.c b/kernel/marker.c
index 50effc0..f211f08 100644
--- a/kernel/marker.c
+++ b/kernel/marker.c
@@ -698,12 +698,11 @@ int marker_probe_unregister(const char *name,
 {
 	struct marker_entry *entry;
 	struct marker_probe_closure *old;
-	int ret = 0;
+	int ret = -ENOENT;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
 	if (!entry) {
-		ret = -ENOENT;
 		goto end;
 	}
 	if (entry->rcu_pending)
@@ -713,12 +712,16 @@ int marker_probe_unregister(const char *name,
 	marker_update_probes();		/* may update entry */
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
+	if (!entry) {
+		goto end;
+	}
 	entry->oldptr = old;
 	entry->rcu_pending = 1;
 	/* write rcu_pending before calling the RCU callback */
 	smp_wmb();
 	call_rcu(&entry->rcu, free_old_closure);
 	remove_marker(name);	/* Ignore busy error message */
+	ret = 0;
 end:
 	mutex_unlock(&markers_mutex);
 	return ret;
--
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