Re: [PATCH 4.9.y] net: sched: prevent UAF on tc_ctl_tfilter when temporarily dropping rtnl_lock

On Mon, May 02, 2022 at 05:49:24PM -0300, Thadeu Lima de Souza Cascardo wrote:

When dropping the rtnl_lock for looking up for a module, the device may be removed, releasing the qdisc and class memory. Right after trying to load the module, cl_ops->put is called, leading to a potential use-after-free.

Though commit e368fdb61d8e ("net: sched: use Qdisc rcu API instead of relying on rtnl lock") fixes this, it involves a lot of refactoring of the net/sched/ code, complicating its backport.

What about 4.14.y? We can not take a commit for 4.9.y with it also being broken in 4.14.y, and yet fixed in 4.19.y, right? Anyone who updates from 4.9 to 4.14 will have a regression.

thanks,

greg k-h