diff mbox series

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

Message ID 20241017123413.4306-2-pablo@netfilter.org (mailing list archive)
State Superseded
Commit 1230fe7ad3974f7bf6c78901473e039b34d4fb1f
Delegated to: Netdev Maintainers
Headers show
Series Netfilter fixes for net | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 5 this patch: 5
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 3 maintainers not CCed: kadlec@netfilter.org coreteam@netfilter.org bpf@vger.kernel.org
netdev/build_clang success Errors and warnings before: 3 this patch: 3
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 4 this patch: 4
netdev/checkpatch warning WARNING: Non-standard signature: Diagnosed-by:
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-10-19--00-00 (tests: 777)

Commit Message

Pablo Neira Ayuso Oct. 17, 2024, 12:34 p.m. UTC 
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 mbox series

Patch

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);
 }