Re: [PATCH net] ipv6: do not set sk_destruct in IPV6_ADDRFORM sockopt

[David Miller <davem@davemloft.net>]

From: Xin Long <lucien.xin@gmail.com>
Date: Mon, 28 Aug 2017 10:45:01 +0800

> ChunYu found a kernel warn_on during syzkaller fuzzing:
> 
> [40226.038539] WARNING: CPU: 5 PID: 23720 at net/ipv4/af_inet.c:152 inet_sock_destruct+0x78d/0x9a0
> [40226.144849] Call Trace:
> [40226.147590]  <IRQ>
> [40226.149859]  dump_stack+0xe2/0x186
> [40226.176546]  __warn+0x1a4/0x1e0
> [40226.180066]  warn_slowpath_null+0x31/0x40
> [40226.184555]  inet_sock_destruct+0x78d/0x9a0
> [40226.246355]  __sk_destruct+0xfa/0x8c0
> [40226.290612]  rcu_process_callbacks+0xaa0/0x18a0
> [40226.336816]  __do_softirq+0x241/0x75e
> [40226.367758]  irq_exit+0x1f6/0x220
> [40226.371458]  smp_apic_timer_interrupt+0x7b/0xa0
> [40226.376507]  apic_timer_interrupt+0x93/0xa0
> 
> The warn_on happned when sk->sk_rmem_alloc wasn't 0 in inet_sock_destruct.
> As after commit f970bd9e3a06 ("udp: implement memory accounting helpers"),
> udp has changed to use udp_destruct_sock as sk_destruct where it would
> udp_rmem_release all rmem.
> 
> But IPV6_ADDRFORM sockopt sets sk_destruct with inet_sock_destruct after
> changing family to PF_INET. If rmem is not 0 at that time, and there is
> no place to release rmem before calling inet_sock_destruct, the warn_on
> will be triggered.
> 
> This patch is to fix it by not setting sk_destruct in IPV6_ADDRFORM sockopt
> any more. As IPV6_ADDRFORM sockopt only works for tcp and udp. TCP sock has
> already set it's sk_destruct with inet_sock_destruct and UDP has set with
> udp_destruct_sock since they're created.
> 
> Fixes: f970bd9e3a06 ("udp: implement memory accounting helpers")
> Reported-by: ChunYu Wang <chunwang@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Applied and queued up for -stable, thanks.