| Message ID | 20241010163414.797374-1-fw@strlen.de |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [nf] netfilter: bpf: must hold reference on net namespace | expand |
On Thu, Oct 10, 2024 at 6:34 PM Florian Westphal <fw@strlen.de> wrote: > > BUG: KASAN: slab-use-after-free in __nf_unregister_net_hook+0x640/0x6b0 > Read of size 8 at addr ffff8880106fe400 by task repro/72= > bpf_nf_link_release+0xda/0x1e0 > bpf_link_free+0x139/0x2d0 > bpf_link_release+0x68/0x80 > __fput+0x414/0xb60 > > Eric says: > It seems that bpf was able to defer the __nf_unregister_net_hook() > after exit()/close() time. > Perhaps a netns reference is missing, because the netns has been > dismantled/freed already. > bpf_nf_link_attach() does : > link->net = net; > But I do not see a reference being taken on net. > > Add such a reference and release it after hook unreg. > Note that I was unable to get syzbot reproducer to work, so I > do not know if this resolves this splat. > > Fixes: 84601d6ee68a ("bpf: add bpf_link support for BPF_NETFILTER programs") > Diagnosed-by: Eric Dumazet <edumazet@google.com> > Reported-by: Lai, Yi <yi1.lai@linux.intel.com> > Signed-off-by: Florian Westphal <fw@strlen.de> SGTM, thanks ! Reviewed-by: Eric Dumazet <edumazet@google.com>
diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c index 5257d5e7eb09..e5e79a08c10b 100644 --- a/net/netfilter/nf_bpf_link.c +++ b/net/netfilter/nf_bpf_link.c @@ -23,6 +23,7 @@ static unsigned int nf_hook_run_bpf(void *bpf_prog, struct sk_buff *skb, struct bpf_nf_link { struct bpf_link link; struct nf_hook_ops hook_ops; + netns_tracker ns_tracker; struct net *net; u32 dead; const struct nf_defrag_hook *defrag_hook; @@ -120,6 +121,7 @@ static void bpf_nf_link_release(struct bpf_link *link) if (!cmpxchg(&nf_link->dead, 0, 1)) { nf_unregister_net_hook(nf_link->net, &nf_link->hook_ops); bpf_nf_disable_defrag(nf_link); + put_net_track(nf_link->net, &nf_link->ns_tracker); } } @@ -257,6 +259,8 @@ int bpf_nf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) return err; } + get_net_track(net, &link->ns_tracker, GFP_KERNEL); + return bpf_link_settle(&link_primer); }
BUG: KASAN: slab-use-after-free in __nf_unregister_net_hook+0x640/0x6b0 Read of size 8 at addr ffff8880106fe400 by task repro/72= bpf_nf_link_release+0xda/0x1e0 bpf_link_free+0x139/0x2d0 bpf_link_release+0x68/0x80 __fput+0x414/0xb60 Eric says: It seems that bpf was able to defer the __nf_unregister_net_hook() after exit()/close() time. Perhaps a netns reference is missing, because the netns has been dismantled/freed already. bpf_nf_link_attach() does : link->net = net; But I do not see a reference being taken on net. Add such a reference and release it after hook unreg. Note that I was unable to get syzbot reproducer to work, so I do not know if this resolves this splat. Fixes: 84601d6ee68a ("bpf: add bpf_link support for BPF_NETFILTER programs") Diagnosed-by: Eric Dumazet <edumazet@google.com> Reported-by: Lai, Yi <yi1.lai@linux.intel.com> Signed-off-by: Florian Westphal <fw@strlen.de> --- net/netfilter/nf_bpf_link.c | 4 ++++ 1 file changed, 4 insertions(+)