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Date:   Tue, 16 Oct 2018 23:23:12 +0300
From:   Matias Karhumaa <matias.karhumaa@gmail.com>
To:     linux-bluetooth@vger.kernel.org
Subject: [PATCH 08/12] btmon: fix segfault caused by integer undeflow
Message-ID: <20181016202312.GA85016@Matias-MacBook-Air.local>
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Fix segfault caused by integer underflow. Fix is to check that
rsp->num_codecs + 3 is not bigger than size before subtracting.

Crash was found by fuzzing btmon with AFL.
---
 monitor/packet.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/monitor/packet.c b/monitor/packet.c
index 461f5e84b..1e9f9d9e4 100644
--- a/monitor/packet.c
+++ b/monitor/packet.c
@@ -5832,6 +5832,11 @@ static void read_local_codecs_rsp(const void *data, uint8_t size)
 	const struct bt_hci_rsp_read_local_codecs *rsp = data;
 	uint8_t i, num_vnd_codecs;
 
+	if (rsp->num_codecs + 3 > size) {
+		print_field("Invalid number of codecs.");
+		return;
+	}
+
 	print_status(rsp->status);
 	print_field("Number of supported codecs: %d", rsp->num_codecs);
 
-- 
2.17.1