[PATCH net 0/1] Netfilter fixes for net

[PATCH net 0/1] Netfilter fixes for net

[Pablo Neira Ayuso]

Hi,

The following series contains one fix:

syzkaller managed to triger UaF due to missing reference on netns in
bpf infrastructure, from Florian Westphal.

Florian Westphal (1):
  netfilter: bpf: must hold reference on net namespace

 net/netfilter/nf_bpf_link.c | 4 ++++
 1 file changed, 4 insertions(+)

-- 
2.30.2

Please, pull these changes from:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git nf-24-10-17

Thanks.

----------------------------------------------------------------

The following changes since commit cb560795c8c2ceca1d36a95f0d1b2eafc4074e37:

  Merge branch 'mlx5-misc-fixes-2024-10-15' (2024-10-17 12:14:11 +0200)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git tags/nf-24-10-17

for you to fetch changes up to 1230fe7ad3974f7bf6c78901473e039b34d4fb1f:

  netfilter: bpf: must hold reference on net namespace (2024-10-17 13:58:57 +0200)

----------------------------------------------------------------
netfilter pull request 24-10-17

----------------------------------------------------------------
Florian Westphal (1):
      netfilter: bpf: must hold reference on net namespace

 net/netfilter/nf_bpf_link.c | 4 ++++
 1 file changed, 4 insertions(+)

[PATCH net 1/1] netfilter: bpf: must hold reference on net namespace

[Pablo Neira Ayuso]

From: Florian Westphal <fw@strlen.de>

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>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_bpf_link.c | 4 ++++
 1 file changed, 4 insertions(+)

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);
 }
 
-- 
2.30.2

Re: [PATCH net 0/1] Netfilter fixes for net

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Pablo Neira Ayuso <pablo@netfilter.org>:

On Thu, 17 Oct 2024 14:34:12 +0200 you wrote:
> Hi,
> 
> The following series contains one fix:
> 
> syzkaller managed to triger UaF due to missing reference on netns in
> bpf infrastructure, from Florian Westphal.
> 
> [...]

Here is the summary with links:
  - [net,1/1] netfilter: bpf: must hold reference on net namespace
    https://git.kernel.org/netdev/net/c/1230fe7ad397

You are awesome, thank you!
-- 
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