[PATCH 4.4 026/160] kprobes: Return error if we fail to reuse kprobe instead of BUG_ON()

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

[ Upstream commit 819319fc93461c07b9cdb3064f154bd8cfd48172 ]

Make reuse_unused_kprobe() to return error code if
it fails to reuse unused kprobe for optprobe instead
of calling BUG_ON().

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
Cc: David S . Miller <davem@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Naveen N . Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/153666124040.21306.14150398706331307654.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/kprobes.c |   27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -665,9 +665,10 @@ static void unoptimize_kprobe(struct kpr
 }
 
 /* Cancel unoptimizing for reusing */
-static void reuse_unused_kprobe(struct kprobe *ap)
+static int reuse_unused_kprobe(struct kprobe *ap)
 {
 	struct optimized_kprobe *op;
+	int ret;
 
 	BUG_ON(!kprobe_unused(ap));
 	/*
@@ -681,8 +682,12 @@ static void reuse_unused_kprobe(struct k
 	/* Enable the probe again */
 	ap->flags &= ~KPROBE_FLAG_DISABLED;
 	/* Optimize it again (remove from op->list) */
-	BUG_ON(!kprobe_optready(ap));
+	ret = kprobe_optready(ap);
+	if (ret)
+		return ret;
+
 	optimize_kprobe(ap);
+	return 0;
 }
 
 /* Remove optimized instructions */
@@ -894,11 +899,16 @@ static void __disarm_kprobe(struct kprob
 #define kprobe_disarmed(p)			kprobe_disabled(p)
 #define wait_for_kprobe_optimizer()		do {} while (0)
 
-/* There should be no unused kprobes can be reused without optimization */
-static void reuse_unused_kprobe(struct kprobe *ap)
+static int reuse_unused_kprobe(struct kprobe *ap)
 {
+	/*
+	 * If the optimized kprobe is NOT supported, the aggr kprobe is
+	 * released at the same time that the last aggregated kprobe is
+	 * unregistered.
+	 * Thus there should be no chance to reuse unused kprobe.
+	 */
 	printk(KERN_ERR "Error: There should be no unused kprobe here.\n");
-	BUG_ON(kprobe_unused(ap));
+	return -EINVAL;
 }
 
 static void free_aggr_kprobe(struct kprobe *p)
@@ -1276,9 +1286,12 @@ static int register_aggr_kprobe(struct k
 			goto out;
 		}
 		init_aggr_kprobe(ap, orig_p);
-	} else if (kprobe_unused(ap))
+	} else if (kprobe_unused(ap)) {
 		/* This probe is going to die. Rescue it */
-		reuse_unused_kprobe(ap);
+		ret = reuse_unused_kprobe(ap);
+		if (ret)
+			goto out;
+	}
 
 	if (kprobe_gone(ap)) {
 		/*