From patchwork Thu Oct 17 12:34:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pablo Neira Ayuso X-Patchwork-Id: 13839937 X-Patchwork-Delegate: kuba@kernel.org Received: from mail.netfilter.org (mail.netfilter.org [217.70.188.207]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0132D1DCB2C; Thu, 17 Oct 2024 12:34:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.188.207 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729168472; cv=none; b=sz9mdsuyZDrQprpWAANF5xHFZL39pBJo8tU5c7c11rDSxesK6NokM1sqmuJmsnAln7rGyLTvxAmxPnNjO9qYp6U64dbx2eQyFEqgaShnq6DNBf08nmq/jv/ZJtxLgwet2rHKkmH5TWLUO/KqnenNR6jNU5VlscTAoqULuBJx1w0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729168472; c=relaxed/simple; bh=gE/KGPEvM1V9/wAW3ScJUD3z+1VvJN5NaMa+a0gpYF8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=sYMx5LMFQ7WU5abBzhxXkdef4IojtndNVliWlGaSonqcMsuhDgMGThVKaUHb1pB31mhaurLsxUXNGk+OzJn2aulLGSJSrsQVktCwdxsi65eiSrwfccZqP2FmhTDKFAtcCBN0AcPU6rk3iA/n/UGFXA6bUmFqZUVxV4ElvBLZv+E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=netfilter.org; arc=none smtp.client-ip=217.70.188.207 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netfilter.org From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, fw@strlen.de Subject: [PATCH net 1/1] netfilter: bpf: must hold reference on net namespace Date: Thu, 17 Oct 2024 14:34:13 +0200 Message-Id: <20241017123413.4306-2-pablo@netfilter.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20241017123413.4306-1-pablo@netfilter.org> References: <20241017123413.4306-1-pablo@netfilter.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org From: Florian Westphal 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 Reported-by: Lai, Yi Signed-off-by: Florian Westphal Reviewed-by: Eric Dumazet Signed-off-by: Pablo Neira Ayuso --- 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); }