Re: [PATCH nf-next] netns: add and use net_ns_barrier

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, May 30, 2017 at 11:38:12AM +0200, Florian Westphal wrote:
> Quoting Joe Stringer:
>   If a user loads nf_conntrack_ftp, sends FTP traffic through a network
>   namespace, destroys that namespace then unloads the FTP helper module,
>   then the kernel will crash.
> 
> Events that lead to the crash:
> 1. conntrack is created with ftp helper in netns x
> 2. This netns is destroyed
> 3. netns destruction is scheduled
> 4. netns destruction wq starts, removes netns from global list
> 5. ftp helper is unloaded, which resets all helpers of the conntracks
> via for_each_net()
> 
> but because netns is already gone from list the for_each_net() loop
> doesn't include it, therefore all of these conntracks are unaffected.
> 
> 6. helper module unload finishes
> 7. netns wq invokes destructor for rmmod'ed helper

Applied, thanks everyone.