[PATCH net-next v2 1/3] tcp_bic: fix divide by zero on max_increment == 0

[Jiayuan Chen]

max_increment is how many packets cwnd can grow per RTT, so 0 makes
no sense, and bictcp_update() divides by it.

Reject values below 1 when the parameter is written.

Fixes: 83803034f423 ("[TCP]: Add TCP BIC congestion control module.")
Reported-by: VEGA <vega@xxxxxxxxxx>
Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
---
Target net-next since it is not a big problem.
---
 net/ipv4/tcp_bic.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index 65444ff142413..27d2e38ff7932 100644
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -27,15 +27,25 @@
 					  */
 
 static int fast_convergence = 1;
-static int max_increment = 16;
+static unsigned int max_increment = 16;
 static int low_window = 14;
 static int beta = 819;		/* = 819/1024 (BICTCP_BETA_SCALE) */
 static int initial_ssthresh;
 static int smooth_part = 20;
 
+static int max_increment_set(const char *val, const struct kernel_param *kp)
+{
+	return param_set_uint_minmax(val, kp, 1, INT_MAX);
+}
+
+static const struct kernel_param_ops max_increment_ops = {
+	.set = max_increment_set,
+	.get = param_get_uint,
+};
+
 module_param(fast_convergence, int, 0644);
 MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
-module_param(max_increment, int, 0644);
+module_param_cb(max_increment, &max_increment_ops, &max_increment, 0644);
 MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search");
 module_param(low_window, int, 0644);
 MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)");
-- 
2.43.0