sock_diag: fix use-after-free read in __sk_free

We must not call sock_diag_has_destroy_listeners(sk) on a socket
that has no reference on net structure.

BUG: KASAN: use-after-free in sock_diag_has_destroy_listeners include/linux/sock_diag.h:75 [inline]
BUG: KASAN: use-after-free in __sk_free+0x329/0x340 net/core/sock.c:1609
Read of size 8 at addr ffff88018a02e3a0 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.17.0-rc5+ #54
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 sock_diag_has_destroy_listeners include/linux/sock_diag.h:75 [inline]
 __sk_free+0x329/0x340 net/core/sock.c:1609
 sk_free+0x42/0x50 net/core/sock.c:1623
 sock_put include/net/sock.h:1664 [inline]
 reqsk_free include/net/request_sock.h:116 [inline]
 reqsk_put include/net/request_sock.h:124 [inline]
 inet_csk_reqsk_queue_drop_and_put net/ipv4/inet_connection_sock.c:672 [inline]
 reqsk_timer_handler+0xe27/0x10e0 net/ipv4/inet_connection_sock.c:739
 call_timer_fn+0x230/0x940 kernel/time/timer.c:1326
 expire_timers kernel/time/timer.c:1363 [inline]
 __run_timers+0x79e/0xc50 kernel/time/timer.c:1666
 run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285
 invoke_softirq kernel/softirq.c:365 [inline]
 irq_exit+0x1d1/0x200 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:525 [inline]
 smp_apic_timer_interrupt+0x17e/0x710 arch/x86/kernel/apic/apic.c:1052
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
 </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffff8801d9ae7c38 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 1ffff1003b35cf8a RCX: 0000000000000000
RDX: 1ffffffff11a30d0 RSI: 0000000000000001 RDI: ffffffff88d18680
RBP: ffff8801d9ae7c38 R08: ffffed003b5e46c3 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffff8801d9ae7cf0 R14: ffffffff897bef20 R15: 0000000000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
 default_idle+0xc2/0x440 arch/x86/kernel/process.c:354
 arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:345
 default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
 cpuidle_idle_call kernel/sched/idle.c:153 [inline]
 do_idle+0x395/0x560 kernel/sched/idle.c:262
 cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:368
 start_secondary+0x426/0x5b0 arch/x86/kernel/smpboot.c:269
 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

Allocated by task 4557:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
 kmem_cache_zalloc include/linux/slab.h:691 [inline]
 net_alloc net/core/net_namespace.c:383 [inline]
 copy_net_ns+0x159/0x4c0 net/core/net_namespace.c:423
 create_new_namespaces+0x69d/0x8f0 kernel/nsproxy.c:107
 unshare_nsproxy_namespaces+0xc3/0x1f0 kernel/nsproxy.c:206
 ksys_unshare+0x708/0xf90 kernel/fork.c:2408
 __do_sys_unshare kernel/fork.c:2476 [inline]
 __se_sys_unshare kernel/fork.c:2474 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:2474
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 69:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
 net_free net/core/net_namespace.c:399 [inline]
 net_drop_ns.part.14+0x11a/0x130 net/core/net_namespace.c:406
 net_drop_ns net/core/net_namespace.c:405 [inline]
 cleanup_net+0x6a1/0xb20 net/core/net_namespace.c:541
 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
 worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
 kthread+0x345/0x410 kernel/kthread.c:240
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

The buggy address belongs to the object at ffff88018a02c140
 which belongs to the cache net_namespace of size 8832
The buggy address is located 8800 bytes inside of
 8832-byte region [ffff88018a02c140, ffff88018a02e3c0)
The buggy address belongs to the page:
page:ffffea0006280b00 count:1 mapcount:0 mapping:ffff88018a02c140 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff88018a02c140 0000000000000000 0000000100000001
raw: ffffea00062a1320 ffffea0006268020 ffff8801d9bdde40 0000000000000000
page dumped because: kasan: bad access detected

Fixes: b922622e ("sock_diag: don't broadcast kernel sockets")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Craig Gallek <kraig@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -1606,7 +1606,7 @@ static void __sk_free(struct sock *sk)
 	if (likely(sk->sk_net_refcnt))
 		sock_inuse_add(sock_net(sk), -1);
 
-	if (unlikely(sock_diag_has_destroy_listeners(sk) && sk->sk_net_refcnt))
+	if (unlikely(sk->sk_net_refcnt && sock_diag_has_destroy_listeners(sk)))
 		sock_diag_broadcast_destroy(sk);
 	else
 		sk_destruct(sk);