Re: [PATCH] net: bonding: avoid use-after-free with tx_hashtbl/rx_hashtbl

Nikolay Aleksandrov
2023-03-28T08:14:09Z

On 28/03/2023 06:40, sujing wrote:
> In bonding mode 6 (Balance-alb),
> there are some potential race conditions between the 'bond_close' process
> and the tx/rx processes that use tx_hashtbl/rx_hashtbl,
> which may lead to use-after-free.

Potential and may? Have you seen it happen and have a trace?

>
> For instance, when the bond6 device is in the 'bond_close' process
> while some backlogged packets from upper level are transmitted

How exactly would that happen? Queues get properly disabled before ndo_stop
is called.

> to 'bond_start_xmit', there is a spinlock contention between
> 'tlb_deinitialize' and 'tlb_choose_channel'.
>
> If 'tlb_deinitialize' preempts the lock before 'tlb_choose_channel',
> a NULL pointer kernel panic will be triggered.
>
> Here's the timeline:
>
> bond_close ------------------ bond_start_xmit
> bond_alb_deinitialize ------- __bond_start_xmit
> tlb_deinitialize ------------ bond_alb_xmit
> spin_lock_bh ---------------- bond_xmit_alb_slave_get
> tx_hashtbl = NULL ----------- tlb_choose_channel
> spin_unlock_bh -------------- //wait for spin_lock_bh
> ------------------------------ spin_lock_bh
> ------------------------------ __tlb_choose_channel
> causing kernel panic ========> tx_hashtbl[hash_index].tx_slave
> ------------------------------ spin_unlock_bh

I don't see how bond_close() can be called in parallel with bond_start_xmit.
Tx queues are disabled and there's a synchronize_rcu() before the device's
ndo_stop is called.

>
> Signed-off-by: sujing <sujing@kylinos.cn>
> ---
> drivers/net/bonding/bond_alb.c | 32 +++++++++------------------
> drivers/net/bonding/bond_main.c | 39 +++++++++++++++++++++++++++------
> include/net/bond_alb.h | 5 ++++-
> 3 files changed, 46 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
> index b9dbad3a8af8..f6ff5ea835c4 100644
> --- a/drivers/net/bonding/bond_alb.c
> +++ b/drivers/net/bonding/bond_alb.c
> @@ -71,7 +71,7 @@ static inline u8 _simple_hash(const u8 *hash_start, int hash_size)
>
> /*********************** tlb specific functions ***************************/
>
> -static inline void tlb_init_table_entry(struct tlb_client_info *entry, int save_load)
> +void tlb_init_table_entry(struct tlb_client_info *entry, int save_load)
> {
> if (save_load) {
> entry->load_history = 1 + entry->tx_bytes /
> @@ -269,8 +269,8 @@ static void rlb_update_entry_from_arp(struct bonding *bond, struct arp_pkt *arp)
> spin_unlock_bh(&bond->mode_lock);
> }
>
> -static int rlb_arp_recv(const struct sk_buff *skb, struct bonding *bond,
> - struct slave *slave)
> +int rlb_arp_recv(const struct sk_buff *skb, struct bonding *bond,
> + struct slave *slave)
> {
> struct arp_pkt *arp, _arp;
>
> @@ -756,7 +756,7 @@ static void rlb_init_table_entry_src(struct rlb_client_info *entry)
> entry->src_next = RLB_NULL_INDEX;
> }
>
> -static void rlb_init_table_entry(struct rlb_client_info *entry)
> +void rlb_init_table_entry(struct rlb_client_info *entry)
> {
> memset(entry, 0, sizeof(struct rlb_client_info));
> rlb_init_table_entry_dst(entry);
> @@ -874,9 +874,6 @@ static int rlb_initialize(struct bonding *bond)
>
> spin_unlock_bh(&bond->mode_lock);
>
> - /* register to receive ARPs */
> - bond->recv_probe = rlb_arp_recv;
> -
> return 0;
> }
>
> @@ -888,7 +885,6 @@ static void rlb_deinitialize(struct bonding *bond)
>
> kfree(bond_info->rx_hashtbl);
> bond_info->rx_hashtbl = NULL;
> - bond_info->rx_hashtbl_used_head = RLB_NULL_INDEX;
>
> spin_unlock_bh(&bond->mode_lock);
> }
> @@ -1303,7 +1299,7 @@ static bool alb_determine_nd(struct sk_buff *skb, struct bonding *bond)
>
> /************************ exported alb functions ************************/
>
> -int bond_alb_initialize(struct bonding *bond, int rlb_enabled)
> +int bond_alb_initialize(struct bonding *bond)
> {
> int res;
>
> @@ -1311,15 +1307,10 @@ int bond_alb_initialize(struct bonding *bond, int rlb_enabled)
> if (res)
> return res;
>
> - if (rlb_enabled) {
> - res = rlb_initialize(bond);
> - if (res) {
> - tlb_deinitialize(bond);
> - return res;
> - }
> - bond->alb_info.rlb_enabled = 1;
> - } else {
> - bond->alb_info.rlb_enabled = 0;
> + res = rlb_initialize(bond);
> + if (res) {
> + tlb_deinitialize(bond);
> + return res;
> }
>
> return 0;
> @@ -1327,12 +1318,9 @@ int bond_alb_initialize(struct bonding *bond, int rlb_enabled)
>
> void bond_alb_deinitialize(struct bonding *bond)
> {
> - struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
> -
> tlb_deinitialize(bond);
>
> - if (bond_info->rlb_enabled)
> - rlb_deinitialize(bond);
> + rlb_deinitialize(bond);
> }
>
> static netdev_tx_t bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 236e5219c811..8fcb5d3ac0a2 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -4217,6 +4217,7 @@ static int bond_open(struct net_device *bond_dev)
> struct bonding *bond = netdev_priv(bond_dev);
> struct list_head *iter;
> struct slave *slave;
> + int i;
>
> if (BOND_MODE(bond) == BOND_MODE_ROUNDROBIN && !bond->rr_tx_counter) {
> bond->rr_tx_counter = alloc_percpu(u32);
> @@ -4239,11 +4240,29 @@ static int bond_open(struct net_device *bond_dev)
> }
>
> if (bond_is_lb(bond)) {
> - /* bond_alb_initialize must be called before the timer
> - * is started.
> - */
> - if (bond_alb_initialize(bond, (BOND_MODE(bond) == BOND_MODE_ALB)))
> - return -ENOMEM;
> + struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
> +
> + spin_lock_bh(&bond->mode_lock);
> +
> + for (i = 0; i < TLB_HASH_TABLE_SIZE; i++)
> + tlb_init_table_entry(&bond_info->tx_hashtbl[i], 0);
> +
> + spin_unlock_bh(&bond->mode_lock);
> +
> + if (BOND_MODE(bond) == BOND_MODE_ALB) {
> + bond->alb_info.rlb_enabled = 1;
> + spin_lock_bh(&bond->mode_lock);
> +
> + bond_info->rx_hashtbl_used_head = RLB_NULL_INDEX;
> + for (i = 0; i < RLB_HASH_TABLE_SIZE; i++)
> + rlb_init_table_entry(bond_info->rx_hashtbl + i);
> +
> + spin_unlock_bh(&bond->mode_lock);
> + bond->recv_probe = rlb_arp_recv;
> + } else {
> + bond->alb_info.rlb_enabled = 0;
> + }
> +
> if (bond->params.tlb_dynamic_lb || BOND_MODE(bond) == BOND_MODE_ALB)
> queue_delayed_work(bond->wq, &bond->alb_work, 0);
> }
> @@ -4279,8 +4298,6 @@ static int bond_close(struct net_device *bond_dev)
>
> bond_work_cancel_all(bond);
> bond->send_peer_notif = 0;
> - if (bond_is_lb(bond))
> - bond_alb_deinitialize(bond);
> bond->recv_probe = NULL;
>
> if (bond_uses_primary(bond)) {
> @@ -5854,6 +5871,8 @@ static void bond_uninit(struct net_device *bond_dev)
> struct list_head *iter;
> struct slave *slave;
>
> + bond_alb_deinitialize(bond);
> +
> bond_netpoll_cleanup(bond_dev);
>
> /* Release the bonded slaves */
> @@ -6295,6 +6314,12 @@ static int bond_init(struct net_device *bond_dev)
> bond_dev->addr_assign_type == NET_ADDR_PERM)
> eth_hw_addr_random(bond_dev);
>
> + /* bond_alb_initialize must be called before the timer
> + * is started.
> + */
> + if (bond_alb_initialize(bond))
> + return -ENOMEM;
> +
> return 0;
> }
>
> diff --git a/include/net/bond_alb.h b/include/net/bond_alb.h
> index 9dc082b2d543..9fd16e20ef82 100644
> --- a/include/net/bond_alb.h
> +++ b/include/net/bond_alb.h
> @@ -150,7 +150,7 @@ struct alb_bond_info {
> */
> };
>
> -int bond_alb_initialize(struct bonding *bond, int rlb_enabled);
> +int bond_alb_initialize(struct bonding *bond);
> void bond_alb_deinitialize(struct bonding *bond);
> int bond_alb_init_slave(struct bonding *bond, struct slave *slave);
> void bond_alb_deinit_slave(struct bonding *bond, struct slave *slave);
> @@ -165,5 +165,8 @@ struct slave *bond_xmit_tlb_slave_get(struct bonding *bond,
> void bond_alb_monitor(struct work_struct *);
> int bond_alb_set_mac_address(struct net_device *bond_dev, void *addr);
> void bond_alb_clear_vlan(struct bonding *bond, unsigned short vlan_id);
> +int rlb_arp_recv(const struct sk_buff *skb, struct bonding *bond, struct slave *slave);
> +void tlb_init_table_entry(struct tlb_client_info *entry, int save_load);
> +void rlb_init_table_entry(struct rlb_client_info *entry);
> #endif /* _NET_BOND_ALB_H */
>