From: Eric Dumazet <edumazet@google.com> mainline inclusion from mainline-v6.17-rc1 commit 88fe14253e181878c2ddb51a298ae8c468a63010 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ID3WJ1 CVE: CVE-2025-40074 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- dst->dev is read locklessly in many contexts, and written in dst_dev_put(). Fixing all the races is going to need many changes. We probably will have to add full RCU protection. Add three helpers to ease this painful process. static inline struct net_device *dst_dev(const struct dst_entry *dst) { return READ_ONCE(dst->dev); } static inline struct net_device *skb_dst_dev(const struct sk_buff *skb) { return dst_dev(skb_dst(skb)); } static inline struct net *skb_dst_dev_net(const struct sk_buff *skb) { return dev_net(skb_dst_dev(skb)); } static inline struct net *skb_dst_dev_net_rcu(const struct sk_buff *skb) { return dev_net_rcu(skb_dst_dev(skb)); } Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()") Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com> Link: https://patch.msgid.link/20250630121934.3399505-7-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Conflicts: net/core/sock.c net/core/dst.c [conflicts due to not merge 15492700ac41 ("tcp: cache RTAX_QUICKACK metric in a hot cache line"), conflicts due to not merge 8a402bbe5476 ("net: dst: annotate data-races around dst->obsolete")] Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- include/net/dst.h | 20 ++++++++++++++++++++ net/core/dst.c | 4 ++-- net/core/sock.c | 8 ++++---- 3 files changed, 26 insertions(+), 6 deletions(-) diff --git a/include/net/dst.h b/include/net/dst.h index badbb80796e4..3e2ff1b9b361 100644 --- a/include/net/dst.h +++ b/include/net/dst.h @@ -579,6 +579,26 @@ static inline void skb_dst_update_pmtu_no_confirm(struct sk_buff *skb, u32 mtu) dst->ops->update_pmtu(dst, NULL, skb, mtu, false); } +static inline struct net_device *dst_dev(const struct dst_entry *dst) +{ + return READ_ONCE(dst->dev); +} + +static inline struct net_device *skb_dst_dev(const struct sk_buff *skb) +{ + return dst_dev(skb_dst(skb)); +} + +static inline struct net *skb_dst_dev_net(const struct sk_buff *skb) +{ + return dev_net(skb_dst_dev(skb)); +} + +static inline struct net *skb_dst_dev_net_rcu(const struct sk_buff *skb) +{ + return dev_net_rcu(skb_dst_dev(skb)); +} + struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie); void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk, struct sk_buff *skb, u32 mtu, bool confirm_neigh); diff --git a/net/core/dst.c b/net/core/dst.c index aad197e761cb..455c8bddc523 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -152,7 +152,7 @@ void dst_dev_put(struct dst_entry *dst) dst->ops->ifdown(dst, dev); dst->input = dst_discard; dst->output = dst_discard_out; - dst->dev = blackhole_netdev; + WRITE_ONCE(dst->dev, blackhole_netdev); netdev_ref_replace(dev, blackhole_netdev, &dst->dev_tracker, GFP_ATOMIC); } @@ -265,7 +265,7 @@ unsigned int dst_blackhole_mtu(const struct dst_entry *dst) { unsigned int mtu = dst_metric_raw(dst, RTAX_MTU); - return mtu ? : dst->dev->mtu; + return mtu ? : dst_dev(dst)->mtu; } EXPORT_SYMBOL_GPL(dst_blackhole_mtu); diff --git a/net/core/sock.c b/net/core/sock.c index 84e3a4be73cd..cbf46bfa5510 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2445,8 +2445,8 @@ static u32 sk_dst_gso_max_size(struct sock *sk, struct dst_entry *dst) !ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)); #endif /* pairs with the WRITE_ONCE() in netif_set_gso(_ipv4)_max_size() */ - max_size = is_ipv6 ? READ_ONCE(dst->dev->gso_max_size) : - READ_ONCE(dst->dev->gso_ipv4_max_size); + max_size = is_ipv6 ? READ_ONCE(dst_dev(dst)->gso_max_size) : + READ_ONCE(dst_dev(dst)->gso_ipv4_max_size); if (max_size > GSO_LEGACY_MAX_SIZE && !sk_is_tcp(sk)) max_size = GSO_LEGACY_MAX_SIZE; @@ -2457,7 +2457,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst) { u32 max_segs = 1; - sk->sk_route_caps = dst->dev->features; + sk->sk_route_caps = dst_dev(dst)->features; if (sk_is_tcp(sk)) sk->sk_route_caps |= NETIF_F_GSO; if (sk->sk_route_caps & NETIF_F_GSO) @@ -2471,7 +2471,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst) sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM; sk->sk_gso_max_size = sk_dst_gso_max_size(sk, dst); /* pairs with the WRITE_ONCE() in netif_set_gso_max_segs() */ - max_segs = max_t(u32, READ_ONCE(dst->dev->gso_max_segs), 1); + max_segs = max_t(u32, READ_ONCE(dst_dev(dst)->gso_max_segs), 1); } } sk->sk_gso_max_segs = max_segs; -- 2.25.1