bonding: fix u32 overflow in compute_gap()

Browse source

The TLB load-tracking fields tx_bytes, load_history, load, and
unbalanced_load are all u32. At sustained throughput above ~3.2 Gbit/s
over the 10-second rebalance interval the byte counters wrap, causing
compute_gap() to produce incorrect gap values and mis-select slaves.
Such speeds are common on modern NICs under heavy traffic.

Widen these fields to u64. Use u64_stats_sync to protect the per-cpu
unbalanced_load_stats against tearing on 32-bit architectures, and
div_u64() for the 64-bit divisions. The tx_bytes and load_history
are protected in spin_lock. Also protect the slave load writing in
bond_alb_monitor() with spin_lock in case of tear on 32-bit.

For compute_gap(), we still use s64 arithmetic throughout, so we can
preserve the existing calculation logic. This order of magnitude is
sufficiently large, there is no need to worry about overflow for now.

Detected by AI code review.

Cc: stable+noautosel@kernel.org # never worked
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Hangbin Liu <liuhangbin@kylinos.cn>
Acked-by: Jay Vosburgh <jv@jvosburgh.net>
Link: https://patch.msgid.link/20260831-bond_overflow-v6-2-ffb0ed1f7268@kylinos.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

This commit is contained in:

Hangbin Liu 2026-08-31 09:51:00 +08:00 • committed by Jakub Kicinski

parent e147615635

commit 4cef95f72b

2 changed files with 39 additions and 18 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

46

drivers/net/bonding/bond_alb.c

View file

11

include/net/bond_alb.h

View file