[PATCH net-next v3 1/3] tcp_bic: fix divide by zero on max_increment == 0
flat view
WARM3d
REVIEWED: 4 (4M)
From: Jiayuan Chen <jiayuan.chen@linux.dev>
Date: 2026-10-08 09:27:02
Also in:
lkml
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
Revision v3 of 3 in this series; 1 review trailer (1 from subsystem maintainers).
Revisions (3)
- v1 [diff vs current]
- v2 [diff vs current]
- v3 current
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 <redacted>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reviewed-by: Eric Dumazet <edumazet@kernel.org>
---
No __MODULE_PARM_TYPE() on purpose, same as dctcp_shift_g in
tcp_dctcp.c. It only changes the type suffix modinfo prints.
---
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