[PATCH 5.10 10/23] batman-adv: prevent ELP transmission interval underflow

[Sven Eckelmann <sven@narfation.org>]

commit 5e50d4b8ae3ea622122d3c6a38d7f6fe68dfddca upstream.

batadv_v_elp_start_timer() enqeues a delayed work. The time when it starts
is randomly chosen between (elp_interval - BATADV_JITTER) and
(elp_interval + BATADV_JITTER). The configured elp_interval must therefore
be larger or equal to BATADV_JITTER to avoid that it causes an underflow of
the unsigned integer. If this would happen, then a "fast" ELP interval
would turn into a "day long" delay.

At the same time, it must not be larger than the maximum value the variable
can store.

Cc: stable@kernel.org
Fixes: a10800829040 ("batman-adv: Add elp_interval hardif genl configuration")
[ Context ]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/netlink.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c
index 0b5cb03859b25..0b10836d85c60 100644
--- a/net/batman-adv/netlink.c
+++ b/net/batman-adv/netlink.c
@@ -939,7 +939,13 @@ static int batadv_netlink_set_hardif(struct sk_buff *skb,
 #ifdef CONFIG_BATMAN_ADV_BATMAN_V
 
 	if (info->attrs[BATADV_ATTR_ELP_INTERVAL]) {
+		u32 elp_interval;
+
 		attr = info->attrs[BATADV_ATTR_ELP_INTERVAL];
+		elp_interval = nla_get_u32(attr);
+
+		elp_interval = min_t(u32, elp_interval, INT_MAX);
+		elp_interval = max_t(u32, elp_interval, BATADV_JITTER);
 
 		atomic_set(&hard_iface->bat_v.elp_interval, nla_get_u32(attr));
 	}
-- 
2.47.3