net: use-after-free in neigh_timer_handler/sock_wfree

[Dmitry Vyukov]

Hello,

I am seeing the following use-after-free report while running
syzkaller fuzzer on
linux-next/3e7350242c6f3d41d28e03418bd781cc1b7bad5f:

==================================================================
BUG: KASAN: use-after-free in constant_test_bit
arch/x86/include/asm/bitops.h:324 [inline] at addr ffff8801c56d5460
BUG: KASAN: use-after-free in sock_flag include/net/sock.h:789
[inline] at addr ffff8801c56d5460
BUG: KASAN: use-after-free in sock_wfree+0x118/0x120
net/core/sock.c:1630 at addr ffff8801c56d5460
Read of size 8 by task syz-fuzzer/3261
CPU: 0 PID: 3261 Comm: syz-fuzzer Not tainted 4.10.0-next-20170224+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __asan_report_load8_noabort+0x29/0x30 mm/kasan/report.c:332
 constant_test_bit arch/x86/include/asm/bitops.h:324 [inline]
 sock_flag include/net/sock.h:789 [inline]
 sock_wfree+0x118/0x120 net/core/sock.c:1630
 skb_release_head_state+0xfc/0x200 net/core/skbuff.c:654
 skb_release_all+0x15/0x60 net/core/skbuff.c:667
 __kfree_skb+0x15/0x20 net/core/skbuff.c:683
 kfree_skb+0x16e/0x4c0 net/core/skbuff.c:704
 ndisc_error_report+0xbb/0x190 net/ipv6/ndisc.c:683
 neigh_invalidate+0x23e/0x570 net/core/neighbour.c:848
 neigh_timer_handler+0x4e7/0x1140 net/core/neighbour.c:933
 call_timer_fn+0x241/0x820 kernel/time/timer.c:1266
 expire_timers kernel/time/timer.c:1305 [inline]
 __run_timers+0x960/0xcf0 kernel/time/timer.c:1599
 run_timer_softirq+0x21/0x80 kernel/time/timer.c:1612
 __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
 invoke_softirq kernel/softirq.c:364 [inline]
 irq_exit+0x1cc/0x200 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:658 [inline]
 smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:962
 apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:707
RIP: 0033:0x46a7c3
RSP: 002b:000000c83e2d5180 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff10
RAX: 0000000000000000 RBX: 000000000046a7b0 RCX: 000000c820471200
RDX: 0000000000000020 RSI: 000000c839e1bba0 RDI: 000000c83e2d5190
RBP: 0000000000000002 R08: 0000000000000002 R09: 0000000000000073
R10: 000000c839a31b03 R11: 000000c839e1bbf8 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000010 R15: 0000000001263e90
 </IRQ>
Object at ffff8801c56d5400, in cache RAWv6 size: 1480
Allocated:
PID = 12540
 kmem_cache_alloc+0x102/0x680 mm/slab.c:3568
 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1332
 sk_alloc+0x8c/0x470 net/core/sock.c:1394
 inet6_create+0x44d/0x1140 net/ipv6/af_inet6.c:183
 __sock_create+0x4e4/0x870 net/socket.c:1197
 sock_create net/socket.c:1237 [inline]
 SYSC_socket net/socket.c:1267 [inline]
 SyS_socket+0xf9/0x230 net/socket.c:1247
 entry_SYSCALL_64_fastpath+0x1f/0xc2
Freed:
PID = 12572
 kasan_slab_free+0x6f/0xb0 mm/kasan/kasan.c:580
 __cache_free mm/slab.c:3510 [inline]
 kmem_cache_free+0x71/0x240 mm/slab.c:3770
 sk_prot_free net/core/sock.c:1375 [inline]
 __sk_destruct+0x487/0x6b0 net/core/sock.c:1450
 sk_destruct+0x47/0x80 net/core/sock.c:1458
 __sk_free+0x57/0x230 net/core/sock.c:1466
 sk_free+0x23/0x30 net/core/sock.c:1477
 sock_put include/net/sock.h:1644 [inline]
 sk_common_release+0x3bf/0x5e0 net/core/sock.c:2781
 rawv6_close+0x4c/0x80 net/ipv6/raw.c:1218
 inet_release+0xed/0x1c0 net/ipv4/af_inet.c:425
 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:432
 sock_release+0x8d/0x1e0 net/socket.c:597
 sock_close+0x16/0x20 net/socket.c:1061
 __fput+0x332/0x7f0 fs/file_table.c:208
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x18a/0x260 kernel/task_work.c:116
 exit_task_work include/linux/task_work.h:21 [inline]
 do_exit+0x1956/0x2900 kernel/exit.c:873
 do_group_exit+0x149/0x420 kernel/exit.c:977
 get_signal+0x7e0/0x1820 kernel/signal.c:2313
 do_signal+0xd2/0x2190 arch/x86/kernel/signal.c:807
 exit_to_usermode_loop+0x200/0x2a0 arch/x86/entry/common.c:156
 prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline]
 syscall_return_slowpath+0x4d3/0x570 arch/x86/entry/common.c:259
 entry_SYSCALL_64_fastpath+0xc0/0xc2