KASAN: use-after-free Read in tomoyo_socket_sendmsg_permission

[Tetsuo Handa]

On 2019/08/09 1:45, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    107e47cc vrf: make sure skb->data contains ip header to ma..
> git tree:       net
> console output: https://syzkaller.appspot.com/x/log.txt?x=139506d8600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4dba67bf8b8c9ad7
> dashboard link: https://syzkaller.appspot.com/bug?extid=b91501546ab4037f685f
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

This is not TOMOYO's bug. LSM modules expect that "struct sock" does not go away.

Also, another use-after-free (presumably on the same "struct sock") was concurrently
inflight at nr_insert_socket() in net/netrom/af_netrom.c . Thus, suspecting netrom's bug.

[  625.441058][    C0] ------------[ cut here ]------------
[  625.446837][    C0] refcount_t: increment on 0; use-after-free.
[  625.461518][    C0] WARNING: CPU: 0 PID: 0 at lib/refcount.c:156 refcount_inc_checked+0x61/0x70
[  625.479173][    C0] Kernel panic - not syncing: panic_on_warn set ...
[  625.746558][    C0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0+ #97
[  625.746575][    C0] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[  625.755731][    C0] Call Trace:
[  625.770091][    C0]  <IRQ>
[  625.777543][    C0]  dump_stack+0x172/0x1f0
[  625.786005][    C0]  ? refcount_inc_not_zero_checked+0x1f0/0x200
[  625.794831][    C0]  panic+0x2dc/0x755
[  625.805217][    C0]  ? add_taint.cold+0x16/0x16
[  625.813697][    C0]  ? __kasan_check_write+0x14/0x20
[  625.822433][    C0]  ? __warn.cold+0x5/0x4c
[  625.832388][    C0]  ? __warn+0xe7/0x1e0
[  625.841820][    C0]  ? refcount_inc_checked+0x61/0x70
[  625.851148][    C0]  __warn.cold+0x20/0x4c
[  625.859701][    C0]  ? vprintk_emit+0x1ea/0x700
[  625.867208][    C0]  ? refcount_inc_checked+0x61/0x70
[  625.875413][    C0]  report_bug+0x263/0x2b0
[  625.884580][    C0]  do_error_trap+0x11b/0x200
[  625.893730][    C0]  do_invalid_op+0x37/0x50
[  625.902936][    C0]  ? refcount_inc_checked+0x61/0x70
[  625.911858][    C0]  invalid_op+0x14/0x20
[  625.920825][    C0] RIP: 0010:refcount_inc_checked+0x61/0x70
[  625.929407][    C0] Code: 1d 3f 6e 64 06 31 ff 89 de e8 cb d2 35 fe 84 db 75 dd e8 82 d1 35 fe 48 c7 c7 40 09 c6 87 c6 05 1f 6e 64 06 01 e8 77 39 07 fe <0f> 0b eb c1 90 90 90 90 90 90 90 90 90 90 90 55 48 89 e5 41 57 41
[  625.937608][    C0] RSP: 0018:ffff8880ae809bf0 EFLAGS: 00010282
[  625.948510][    C0] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[  625.957237][    C0] RDX: 0000000000000100 RSI: ffffffff815c3a26 RDI: ffffed1015d01370
[  625.967249][    C0] RBP: ffff8880ae809c00 R08: ffffffff88c7a1c0 R09: fffffbfff14a775b
[  625.991542][    C0] R10: fffffbfff14a775a R11: ffffffff8a53bad7 R12: ffff8880a066f480
[  626.002193][    C0] R13: ffff8880a066f468 R14: ffff88808d69ef48 R15: ffff88808d69ef20
[  626.014844][    C0]  ? vprintk_func+0x86/0x189
[  626.027298][    C0]  nr_insert_socket+0x2d/0xe0
[  626.041237][    C0]  nr_rx_frame+0x1605/0x1e73
[  626.051737][    C0]  nr_loopback_timer+0x7b/0x170
[  626.073842][    C0]  call_timer_fn+0x1ac/0x780
[  626.092970][    C0]  ? nr_process_rx_frame+0x1540/0x1540
[  626.108552][    C0]  ? msleep_interruptible+0x150/0x150
[  626.118574][    C0]  ? run_timer_softirq+0x685/0x17a0
[  626.131811][    C0]  ? trace_hardirqs_on+0x67/0x240
[  626.145424][    C0]  ? __kasan_check_read+0x11/0x20
[  626.156592][    C0]  ? nr_process_rx_frame+0x1540/0x1540
[  626.164362][    C0]  ? nr_process_rx_frame+0x1540/0x1540
[  626.175423][    C0]  run_timer_softirq+0x697/0x17a0
[  626.188804][    C0]  ? add_timer+0x930/0x930
[  626.202652][    C0]  ? kvm_clock_read+0x18/0x30
[  626.215813][    C0]  ? kvm_sched_clock_read+0x9/0x20
[  626.231378][    C0]  ? sched_clock+0x2e/0x50
[  626.231395][    C0]  ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
[  626.231408][    C0]  ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
[  626.231432][    C0]  __do_softirq+0x262/0x98c
[  626.244512][    C0]  ? sched_clock_cpu+0x1b/0x1b0
[  626.244531][    C0]  irq_exit+0x19b/0x1e0
[  626.244545][    C0]  smp_apic_timer_interrupt+0x1a3/0x610
[  626.244558][    C0]  apic_timer_interrupt+0xf/0x20
[  626.244563][    C0]  </IRQ>
[  626.244579][    C0] RIP: 0010:native_safe_halt+0xe/0x10
[  626.244606][    C0] Code: b8 94 73 fa eb 8a 90 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 34 25 4f 00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d 24 25 4f 00 fb f4 <c3> 90 55 48 89 e5 41 57 41 56 41 55 41 54 53 e8 0e 56 27 fa e8 c9
[  626.257081][    C0] RSP: 0018:ffffffff88c07ce8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
[  626.269812][    C0] RAX: 1ffffffff11a5e05 RBX: ffffffff88c7a1c0 RCX: 0000000000000000
[  626.281053][    C0] RDX: dffffc0000000000 RSI: 0000000000000006 RDI: ffffffff88c7aa4c
[  626.290913][    C0] RBP: ffffffff88c07d18 R08: ffffffff88c7a1c0 R09: 0000000000000000
[  626.303361][    C0] R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
[  626.314081][    C0] R13: ffffffff89a4f778 R14: 0000000000000000 R15: 0000000000000000
[  626.314116][    C0]  ? default_idle+0x4e/0x360
[  626.323075][    C0]  arch_cpu_idle+0xa/0x10
[  626.333543][    C0]  default_idle_call+0x84/0xb0
[  626.341839][    C0]  do_idle+0x413/0x760
[  626.370736][    C0]  ? retint_kernel+0x2b/0x2b
[  626.383044][    C0]  ? arch_cpu_idle_exit+0x80/0x80
[  626.400071][    C0]  ? do_idle+0x387/0x760
[  626.418085][    C0]  cpu_startup_entry+0x1b/0x20
[  626.431835][    C0]  rest_init+0x245/0x37b
[  626.459420][    C0]  arch_call_rest_init+0xe/0x1b
[  626.471993][    C0]  start_kernel+0x912/0x951
[  626.482387][    C0]  ? mem_encrypt_init+0xb/0xb
[  626.495105][    C0]  ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
[  626.507125][    C0]  ? x86_family+0x41/0x50
[  626.519773][    C0]  ? __sanitizer_cov_trace_const_cmp1+0x1a/0x20
[  626.532837][    C0]  x86_64_start_reservations+0x29/0x2b
[  626.545019][    C0]  x86_64_start_kernel+0x77/0x7b
[  626.558711][    C0]  secondary_startup_64+0xa4/0xb0
[  626.897092][    C0] Kernel Offset: disabled
[  626.901428][    C0] Rebooting in 86400 seconds..