Re: [PATCH net] bonding: fix u32 overflow in compute_gap()

[Jakub Kicinski]

On Mon, 10 Aug 2026 10:38:23 +0800 Hangbin Liu wrote:
> From: Hangbin Liu <liuhangbin@xxxxxxxxxx>
> 
> compute_gap() computes the gap between a slave's link capacity and its
> current TLB load. Both terms use u32 left-shifts that overflow on modern
> hardware:
> 
>   - slave->speed is u32 in Mbps; speed << 20 overflows at > 4Gbps.
>   - SLAVE_TLB_INFO(slave).load is u32; load << 3 overflows at > 512M.
> 
> Cast both operands to s64 before shifting so the arithmetic is performed
> in 64 bits. Also update the comment to make it more clear.

Could you clarify the impact in the commit message a little more
explicitly? If the links are the same speed -- does this fix still
matter?

AI over here says:

  The fix is incomplete for very high loads: each hash bucket’s u32 tx_bytes
  already wraps above roughly 3.44 Gbit/s sustained over the 10-second interval,
  and aggregate u32 load wraps above roughly 34.4 Gbit/s.

While these are not exactly the same lines of code - I think it'd be
worth to address them all in one series. 

> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Hangbin Liu <liuhangbin@xxxxxxxxxx>

Oh, you work at KylinOS now -- please clearly state in the commit
message if the issue was seen in real life or AI-detected.