Subject: Re: [PATCH net-next v3 5/6] bonding: Mark active offloaded xfrm_states

From: Hangbin Liu <[email-masked]>
Date: Fri, 11 Apr 2025 09:08:58 +0000

On Fri, Apr 11, 2025 at 10:49:57AM +0300, Cosmin Ratiu wrote:
> When the active link is changed for a bond device, the existing xfrm
> states need to be migrated over to the new link. This is done with:
> - bond_ipsec_del_sa_all() goes through the offloaded states list and
>   removes all of them from hw.
> - bond_ipsec_add_sa_all() re-offloads all states to the new device.
> 
> But because the offload status of xfrm states isn't marked in any way,
> there can be bugs.
> 
> When all bond links are down, bond_ipsec_del_sa_all() unoffloads
> everything from the previous active link. If the same link then comes
> back up, nothing gets reoffloaded by bond_ipsec_add_sa_all().
> This results in a stack trace like this a bit later when user space
> removes the offloaded rules, because mlx5e_xfrm_del_state() is asked to
> remove a rule that's no longer offloaded:
> 
>  [] Call Trace:
>  []  <TASK>
>  []  ? __warn+0x7d/0x110
>  []  ? mlx5e_xfrm_del_state+0x90/0xa0 [mlx5_core]
>  []  ? report_bug+0x16d/0x180
>  []  ? handle_bug+0x4f/0x90
>  []  ? exc_invalid_op+0x14/0x70
>  []  ? asm_exc_invalid_op+0x16/0x20
>  []  ? mlx5e_xfrm_del_state+0x73/0xa0 [mlx5_core]
>  []  ? mlx5e_xfrm_del_state+0x90/0xa0 [mlx5_core]
>  []  bond_ipsec_del_sa+0x1ab/0x200 [bonding]
>  []  xfrm_dev_state_delete+0x1f/0x60
>  []  __xfrm_state_delete+0x196/0x200
>  []  xfrm_state_delete+0x21/0x40
>  []  xfrm_del_sa+0x69/0x110
>  []  xfrm_user_rcv_msg+0x11d/0x300
>  []  ? release_pages+0xca/0x140
>  []  ? copy_to_user_tmpl.part.0+0x110/0x110
>  []  netlink_rcv_skb+0x54/0x100
>  []  xfrm_netlink_rcv+0x31/0x40
>  []  netlink_unicast+0x1fc/0x2d0
>  []  netlink_sendmsg+0x1e4/0x410
>  []  __sock_sendmsg+0x38/0x60
>  []  sock_write_iter+0x94/0xf0
>  []  vfs_write+0x338/0x3f0
>  []  ksys_write+0xba/0xd0
>  []  do_syscall_64+0x4c/0x100
>  []  entry_SYSCALL_64_after_hwframe+0x4b/0x53
> 
> There's also another theoretical bug:
> Calling bond_ipsec_del_sa_all() multiple times can result in corruption
> in the driver implementation if the double-free isn't tolerated. This
> isn't nice.
> 
> Before the "Fixes" commit, xs->xso.real_dev was set to NULL when an xfrm
> state was unoffloaded from a device, but a race with netdevsim's
> .xdo_dev_offload_ok() accessing real_dev was considered a sufficient
> reason to not set real_dev to NULL anymore. This unfortunately
> introduced the new bugs.
> 
> Since .xdo_dev_offload_ok() was significantly refactored by [1] and
> there are no more users in the stack of xso.real_dev, that
> race is now gone and xs->xso.real_dev can now once again be used to
> represent which device (if any) currently holds the offloaded rule.
> 
> Go one step further and set real_dev after add/before delete calls, to
> catch any future driver misuses of real_dev.
> 
> [1] https://lore.kernel.org/netdev/[email-masked]/
> Fixes: f8cde9805981 ("bonding: fix xfrm real_dev null pointer dereference")
> Signed-off-by: Cosmin Ratiu <[email-masked]>
> Reviewed-by: Leon Romanovsky <[email-masked]>
> ---
>  drivers/net/bonding/bond_main.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 4ba525a564c5..14f7c9712ad4 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -496,9 +496,9 @@ static int bond_ipsec_add_sa(struct net_device *bond_dev,
>  		goto out;
>  	}
>  
> -	xs->xso.real_dev = real_dev;
>  	err = real_dev->xfrmdev_ops->xdo_dev_state_add(real_dev, xs, extack);
>  	if (!err) {
> +		xs->xso.real_dev = real_dev;
>  		ipsec->xs = xs;
>  		INIT_LIST_HEAD(&ipsec->list);
>  		mutex_lock(&bond->ipsec_lock);
> @@ -540,12 +540,12 @@ static void bond_ipsec_add_sa_all(struct bonding *bond)
>  		if (ipsec->xs->xso.real_dev == real_dev)
>  			continue;
>  
> -		ipsec->xs->xso.real_dev = real_dev;
>  		if (real_dev->xfrmdev_ops->xdo_dev_state_add(real_dev,
>  							     ipsec->xs, NULL)) {
>  			slave_warn(bond_dev, real_dev, "%s: failed to add SA\n", __func__);
> -			ipsec->xs->xso.real_dev = NULL;
> +			continue;
>  		}
> +		ipsec->xs->xso.real_dev = real_dev;
>  	}
>  out:
>  	mutex_unlock(&bond->ipsec_lock);
> @@ -629,6 +629,7 @@ static void bond_ipsec_del_sa_all(struct bonding *bond)
>  				   __func__);
>  			continue;
>  		}
> +		ipsec->xs->xso.real_dev = NULL;
>  		real_dev->xfrmdev_ops->xdo_dev_state_delete(real_dev,
>  							    ipsec->xs);
>  		if (real_dev->xfrmdev_ops->xdo_dev_state_free)
> @@ -664,6 +665,7 @@ static void bond_ipsec_free_sa(struct net_device *bond_dev,
>  
>  	WARN_ON(xs->xso.real_dev != real_dev);
>  
> +	xs->xso.real_dev = NULL;
>  	if (real_dev && real_dev->xfrmdev_ops &&
>  	    real_dev->xfrmdev_ops->xdo_dev_state_free)
>  		real_dev->xfrmdev_ops->xdo_dev_state_free(real_dev, xs);
> -- 
> 2.45.0
> 

Tested-by: Hangbin Liu <[email-masked]>
Reviewed-by: Hangbin Liu <[email-masked]>