linux-kernel - [PATCH 3.16 101/305] batman-adv: Fix integer overflow in batadv_iv_ogm_calc

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Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Antonio Quartulli" <a@...table.cc>,
	"Marek Lindner" <mareklindner@...mailbox.ch>,
	"Sven Eckelmann" <sven.eckelmann@...n-mesh.com>
Subject: [PATCH 3.16 101/305] batman-adv: Fix integer overflow in
 batadv_iv_ogm_calc_tq

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Sven Eckelmann <sven.eckelmann@...n-mesh.com>

commit d285f52cc0f23564fd61976d43fd5b991b4828f6 upstream.

The undefined behavior sanatizer detected an signed integer overflow in a
setup with near perfect link quality

    UBSAN: Undefined behaviour in net/batman-adv/bat_iv_ogm.c:1246:25
    signed integer overflow:
    8713350 * 255 cannot be represented in type 'int'

The problems happens because the calculation of mixed unsigned and signed
integers resulted in an integer multiplication.

      batadv_ogm_packet::tq (u8 255)
    * tq_own (u8 255)
    * tq_asym_penalty (int 134; max 255)
    * tq_iface_penalty (int 255; max 255)

The tq_iface_penalty, tq_asym_penalty and inv_asym_penalty can just be
changed to unsigned int because they are not expected to become negative.

Fixes: c039876892e3 ("batman-adv: add WiFi penalty")
Signed-off-by: Sven Eckelmann <sven.eckelmann@...n-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@...mailbox.ch>
Signed-off-by: Antonio Quartulli <a@...table.cc>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/batman-adv/bat_iv_ogm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -1134,9 +1134,10 @@ static int batadv_iv_ogm_calc_tq(struct
 	uint8_t total_count;
 	uint8_t orig_eq_count, neigh_rq_count, neigh_rq_inv, tq_own;
 	unsigned int neigh_rq_inv_cube, neigh_rq_max_cube;
-	int tq_asym_penalty, inv_asym_penalty, if_num, ret = 0;
+	int if_num, ret = 0;
+	unsigned int tq_asym_penalty, inv_asym_penalty;
 	unsigned int combined_tq;
-	int tq_iface_penalty;
+	unsigned int tq_iface_penalty;
 
 	/* find corresponding one hop neighbor */
 	rcu_read_lock();