| Message ID | tencent_CD037FFEEB8CA462C8403FB30F50EEC6DF06@qq.com |
|---|---|
| State | New |
| Headers | show |
| Series | [6.1] netfilter: nf_tables: fix UAF in nf_tables_netdev_event walker | expand |
On Thu, Oct 01, 2026 at 11:51:30AM +0800, Ma Xinmeng wrote: > This is a 6.1-only fix. Mainline already fixed this bug in fc0133428e7a > ("netfilter: nf_tables: Tolerate chains with no remaining hooks"), which > 6.1 cannot take because it lacks 207296f1a03b ("netfilter: nf_tables: > allow to create netdev chain without device") and b9703ed44ffb > ("netfilter: nf_tables: support for adding new devices to an existing > netdev chain"). Then, why not add those patches you refer to as -stable dependencies? -stable trees will become hard to maintain if they start deviating too much from upstream. > So 6.1 keeps dropping the chain on the last > NETDEV_UNREGISTER, and this patch only makes the walker safe. > > nf_tables_netdev_event() walks table->chains with > list_for_each_entry_safe(). On the last NETDEV_UNREGISTER for a base > chain, nft_netdev_event() calls __nft_release_basechain(), which removes > that base chain (nft_chain_del()) and destroys its rules. A JUMP/GOTO rule > targeting an NFT_CHAIN_BINDING chain deactivates and frees that successor > (nft_immediate_destroy() -> nf_tables_chain_destroy()), so the walker's > saved "nr" iterator can point at freed memory, triggering a > slab-use-after-free. > > Fix it by restarting the table->chains walk whenever nft_netdev_event() > released a chain. __nft_release_basechain() removes the base chain from > the list before returning, so a restart cannot revisit the freed chain and > the walk terminates. > > Signed-off-by: Ma Xinmeng <1564938642@qq.com> > --- > net/netfilter/nft_chain_filter.c | 14 +++++++++----- > 1 file changed, 9 insertions(+), 5 deletions(-) > > diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c > index d170758..ca6450a 100644 > --- a/net/netfilter/nft_chain_filter.c > +++ b/net/netfilter/nft_chain_filter.c > @@ -318,7 +318,7 @@ static const struct nft_chain_type nft_chain_filter_netdev = { > }, > }; > > -static void nft_netdev_event(unsigned long event, struct net_device *dev, > +static bool nft_netdev_event(unsigned long event, struct net_device *dev, > struct nft_ctx *ctx) > { > struct nft_base_chain *basechain = nft_base_chain(ctx->chain); > @@ -326,7 +326,7 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, > int n = 0; > > if (event != NETDEV_UNREGISTER) > - return; > + return false; > > list_for_each_entry(hook, &basechain->hook_list, list) { > if (hook->ops.dev == dev) > @@ -335,7 +335,7 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, > n++; > } > if (!found) > - return; > + return false; > > if (n > 1) { > if (!(ctx->chain->table->flags & NFT_TABLE_F_DORMANT)) > @@ -343,7 +343,7 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, > > list_del_rcu(&found->list); > kfree_rcu(found, rcu); > - return; > + return false; > } > > /* UNREGISTER events are also happening on netns exit. > @@ -353,6 +353,8 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, > * so we cannot skip exiting net namespaces. > */ > __nft_release_basechain(ctx); > + > + return true; > } > > static int nf_tables_netdev_event(struct notifier_block *this, > @@ -380,6 +382,7 @@ static int nf_tables_netdev_event(struct notifier_block *this, > > ctx.family = table->family; > ctx.table = table; > +restart: > list_for_each_entry_safe(chain, nr, &table->chains, list) { > if (!nft_is_base_chain(chain)) > continue; > @@ -390,7 +393,8 @@ static int nf_tables_netdev_event(struct notifier_block *this, > continue; > > ctx.chain = chain; > - nft_netdev_event(event, dev, &ctx); > + if (nft_netdev_event(event, dev, &ctx)) > + goto restart; > } > } > mutex_unlock(&nft_net->commit_mutex); > -- > 2.49.0.windows.1 >
diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c index d170758..ca6450a 100644 --- a/net/netfilter/nft_chain_filter.c +++ b/net/netfilter/nft_chain_filter.c @@ -318,7 +318,7 @@ static const struct nft_chain_type nft_chain_filter_netdev = { }, }; -static void nft_netdev_event(unsigned long event, struct net_device *dev, +static bool nft_netdev_event(unsigned long event, struct net_device *dev, struct nft_ctx *ctx) { struct nft_base_chain *basechain = nft_base_chain(ctx->chain); @@ -326,7 +326,7 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, int n = 0; if (event != NETDEV_UNREGISTER) - return; + return false; list_for_each_entry(hook, &basechain->hook_list, list) { if (hook->ops.dev == dev) @@ -335,7 +335,7 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, n++; } if (!found) - return; + return false; if (n > 1) { if (!(ctx->chain->table->flags & NFT_TABLE_F_DORMANT)) @@ -343,7 +343,7 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, list_del_rcu(&found->list); kfree_rcu(found, rcu); - return; + return false; } /* UNREGISTER events are also happening on netns exit. @@ -353,6 +353,8 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, * so we cannot skip exiting net namespaces. */ __nft_release_basechain(ctx); + + return true; } static int nf_tables_netdev_event(struct notifier_block *this, @@ -380,6 +382,7 @@ static int nf_tables_netdev_event(struct notifier_block *this, ctx.family = table->family; ctx.table = table; +restart: list_for_each_entry_safe(chain, nr, &table->chains, list) { if (!nft_is_base_chain(chain)) continue; @@ -390,7 +393,8 @@ static int nf_tables_netdev_event(struct notifier_block *this, continue; ctx.chain = chain; - nft_netdev_event(event, dev, &ctx); + if (nft_netdev_event(event, dev, &ctx)) + goto restart; } } mutex_unlock(&nft_net->commit_mutex);
This is a 6.1-only fix. Mainline already fixed this bug in fc0133428e7a ("netfilter: nf_tables: Tolerate chains with no remaining hooks"), which 6.1 cannot take because it lacks 207296f1a03b ("netfilter: nf_tables: allow to create netdev chain without device") and b9703ed44ffb ("netfilter: nf_tables: support for adding new devices to an existing netdev chain"). So 6.1 keeps dropping the chain on the last NETDEV_UNREGISTER, and this patch only makes the walker safe. nf_tables_netdev_event() walks table->chains with list_for_each_entry_safe(). On the last NETDEV_UNREGISTER for a base chain, nft_netdev_event() calls __nft_release_basechain(), which removes that base chain (nft_chain_del()) and destroys its rules. A JUMP/GOTO rule targeting an NFT_CHAIN_BINDING chain deactivates and frees that successor (nft_immediate_destroy() -> nf_tables_chain_destroy()), so the walker's saved "nr" iterator can point at freed memory, triggering a slab-use-after-free. Fix it by restarting the table->chains walk whenever nft_netdev_event() released a chain. __nft_release_basechain() removes the base chain from the list before returning, so a restart cannot revisit the freed chain and the walk terminates. Signed-off-by: Ma Xinmeng <1564938642@qq.com> --- net/netfilter/nft_chain_filter.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)