Re: [PATCH v1] RDMA/rxe: unpublish the per-net tunnel socket before

[Zhu Yanjun <yanjun.zhu@linux.dev>]

在 2026/9/22 22:18, Binbin Deng 写道:
> KASAN reports a slab-use-after-free in ip6_route_output_flags()
> reached from rxe_find_route(), with the free in __sk_destruct() after
> rxe_sock_put(), and a user with CAP_NET_ADMIN can remove the device with
> "rdma link del rxe0" while RoCE v2 over IPv6 traffic keeps looking the
> socket up.
>
> BUG: KASAN: slab-use-after-free in ip6_route_output_flags+0x300/0x360
> Read of size 4 at addr ffff888115ddd794 by task kworker/u32:6/309
> Call Trace:
>   <TASK>
>   dump_stack_lvl+0x53/0x70
>   print_report+0xd0/0x630
>   ? __pfx__raw_spin_lock_irqsave+0x10/0x10
>   ? ip6_route_output_flags+0x300/0x360
>   kasan_report+0xce/0x100
>   ? ip6_route_output_flags+0x300/0x360
>   ip6_route_output_flags+0x300/0x360
>   ip6_dst_lookup_tail.constprop.0+0x76c/0xcc0
>   ? ct_nmi_exit+0xc3/0xf0
>   ip6_dst_lookup_flow+0xf5/0x1e0
>   ? __pfx_ip6_dst_lookup_flow+0x10/0x10
>   rxe_find_route+0x426/0xa30
>   ? __kasan_slab_alloc+0x6e/0x70
>   ? __pfx_rxe_find_route+0x10/0x10
>   ? kmem_cache_alloc_node_noprof+0x141/0x370
>   ? kmalloc_reserve+0x103/0x2b0
>   ? rxe_icrc_generate+0x229/0x330
>   ? __pfx___alloc_skb+0x10/0x10
>   rxe_prepare+0x9e8/0x18b0
>   ? rxe_init_packet+0x3c7/0x4f0
>   rxe_requester+0x1a0f/0x51f0
>   ? rxe_completer+0x1de9/0x38c0
>   ? __pfx_rxe_completer+0x10/0x10
>   ? __queue_work+0x43e/0x11f0
>   ? __pfx_rxe_requester+0x10/0x10
>   ? irqentry_exit+0xd2/0x640
>   ? _raw_spin_lock_irqsave+0x85/0xe0
>   ? __pfx__raw_spin_lock_irqsave+0x10/0x10
>   ? __pfx_rxe_sender+0x10/0x10
>   rxe_sender+0xe/0x30
>   do_work+0x144/0x470
>   process_one_work+0x633/0x1030
>   ? assign_work+0x11d/0x370
>   worker_thread+0x45b/0xd10
>   ? __pfx_worker_thread+0x10/0x10
>   kthread+0x2c6/0x3b0
>   ? recalc_sigpending+0x15c/0x1e0
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork+0x36e/0x5a0
>   ? __pfx_ret_from_fork+0x10/0x10
>   ? __switch_to+0x572/0xdd0
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork_asm+0x1a/0x30
>   </TASK>
>
> Allocated by task 146020:
>   kasan_save_stack+0x33/0x60
>   kasan_save_track+0x14/0x30
>   __kasan_slab_alloc+0x6e/0x70
>   kmem_cache_alloc_noprof+0x130/0x360
>   sk_prot_alloc+0x56/0x210
>
> Fix by clearing the per-net pointer before the last reference is dropped.

Thanks a lot. I also confronted this problem. I fixed this problem with 
a lock.

It seems that this fix is better. If this fix is verified in your test 
environment,

I am ok with this fix.

Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>

Thanks a lot.

Zhu Yanjun

>
> Fixes: f1327abd6abed ("RDMA/rxe: Support RDMA link creation and destruction per net namespace")
> Signed-off-by: Binbin Deng <18983559317@163.com>
> ---
>   drivers/infiniband/sw/rxe/rxe_net.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
> index 53daaf4c1eb2..4153f03ed69a 100644
> --- a/drivers/infiniband/sw/rxe/rxe_net.c
> +++ b/drivers/infiniband/sw/rxe/rxe_net.c
> @@ -638,9 +638,15 @@ static void rxe_sock_put(struct sock *sk,
>   	if (refcount_read(&sk->sk_refcnt) > SK_REF_FOR_TUNNEL) {
>   		__sock_put(sk);
>   	} else {
> +		/*
> +		 * Clear the per-net pointer before the last reference is
> +		 * dropped.  rxe_ns_pernet_sk4/6() returns the pointer to readers
> +		 * that dereference it outside the RCU read-side critical section,
> +		 * so it must not stay visible once the socket has entered the
> +		 * teardown path.
> +		 */
> +		set_sk(net, NULL);
>   		rxe_release_udp_tunnel(sk);
> -		sk = NULL;
> -		set_sk(net, sk);
>   	}
>   }
>   

-- 
Best Regards,
Yanjun.Zhu