Re: [PATCH net-next v2] ipv4: igmp: remove multicast group from hash table on device destruction

[Ido Schimmel]

On Tue, Jun 30, 2026 at 04:55:22PM +0900, Yuyang Huang wrote:
> > Hi,
> >
> > why sending this to net-next not to net if that's a bug fix?
> >
> > In the v1 thread it was said
> > >This is a long-standing bug, not a recent regression.
> >
> > so why do not cc stable kernel to get rid of this bug from
> > stable kernels in such case?
> 
> Thanks for the advise, will send this patch to stable kernel.

Please target v3 at net and add a trace given you're claiming for a
use-after-free. That way we know that the problem is real and not a
false-positive from some tool. You can reproduce it by adding enough
delay in inetdev_destroy():

BUG: KASAN: slab-use-after-free in ip_check_mc_rcu+0x2cc/0x500
Read of size 4 at addr ffff88810c571208 by task mausezahn/419

CPU: 2 UID: 0 PID: 419 Comm: mausezahn Not tainted 7.1.0-virtme-g15d4a7c23bf6 #17 PREEMPT(lazy)
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
 <IRQ>
 dump_stack_lvl+0x4d/0x70
 print_report+0x153/0x4c2
 kasan_report+0xda/0x110
 ip_check_mc_rcu+0x2cc/0x500
 ip_route_input_rcu.part.0+0x13d/0xbc0
 ip_route_input_noref+0xb6/0x110
 ip_rcv_finish_core+0x41b/0x1d90
 ip_rcv_finish+0xea/0x1b0
 ip_rcv+0xb7/0x1b0
 __netif_receive_skb_one_core+0xfc/0x180
 process_backlog+0x1ea/0x5e0
 __napi_poll+0x97/0x480
 net_rx_action+0x97c/0xfa0
 handle_softirqs+0x18c/0x4f0
 do_softirq+0x42/0x60
 </IRQ>