Re: [PATCH net] net: dcb: flush rewrite table on device unregister

[Petr Machata]

Wenbo Sun <sunwenbo@xxxxxxxxxxxxxxxxxxxx> writes:

> In dcbnl_flush_dev(), which is called upon NETDEV_UNREGISTER for net
> devices with dcbnl_ops, only entries in dcb_app_list matching
> dev->ifindex are freed. The entries in dcb_rewr_list added via
> dcb_setrewr() are not flushed.
>
> This causes a memory leak of struct dcb_app_type nodes in dcb_rewr_list
> when a DCB-capable net device is unregistered, and leaves stale entries
> in the global rewrite table that could inappropriately match if another
> net device later reuses the same ifindex.
>
> Iterate over dcb_rewr_list in dcbnl_flush_dev() and remove and free all
> entries matching dev->ifindex, mirroring the cleanup performed for
> dcb_app_list.
>
> This issue was found via LLM-assisted code review, confirmed by
> reproducing the leaked rewrite table entry upon netdevice unregistration
> in a User-Mode Linux (ARCH=um) environment, and verified in UML by
> confirming that all rewrite table entries for the unregistered netdevice
> are flushed.
>
> Fixes: 622f1b2fae2e ("net: dcb: add new rewrite table")
> Signed-off-by: Wenbo Sun <sunwenbo@xxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Petr Machata <petrm@xxxxxxxxxx>

However, this has never worked, is therefore not a regression, and
should target net-next.