[PATCH 3.16 101/305] batman-adv: Fix integer overflow in batadv_iv_ogm_calc_tq

Ben Hutchings
2016-08-14T10:58:16Z

From: Sven Eckelmann <sven.eckelmann@open-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@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.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();