Re: [PATCH net] VSOCK: check sk state before receive

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Sun, May 27, 2018 at 11:29:45PM +0800, Hangbin Liu wrote:
> Hmm...Although I won't reproduce this bug with my reproducer after
> apply my patch. I could still get a similiar issue with syzkaller sock vnet test.
> 
> It looks this patch is not complete. Here is the KASAN call trace with my patch.
> I can also reproduce it without my patch.

Seems like a race between vmci_datagram_destroy_handle() and the
delayed callback, vmci_transport_recv_dgram_cb().

I don't know the VMCI transport well so I'll leave this to Jorgen.

> ==================================================================
> BUG: KASAN: use-after-free in vmci_transport_allow_dgram.part.7+0x155/0x1a0 [vmw_vsock_vmci_transport]
> Read of size 4 at addr ffff880026a3a914 by task kworker/0:2/96
> 
> CPU: 0 PID: 96 Comm: kworker/0:2 Not tainted 4.17.0-rc6.vsock+ #28
> Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> Workqueue: events dg_delayed_dispatch [vmw_vmci]
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0xdd/0x18e lib/dump_stack.c:113
>  print_address_description+0x7a/0x3e0 mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report+0x1dd/0x460 mm/kasan/report.c:412
>  vmci_transport_allow_dgram.part.7+0x155/0x1a0 [vmw_vsock_vmci_transport]
>  vmci_transport_recv_dgram_cb+0x5d/0x200 [vmw_vsock_vmci_transport]
>  dg_delayed_dispatch+0x99/0x1b0 [vmw_vmci]
>  process_one_work+0xa4e/0x1720 kernel/workqueue.c:2145
>  worker_thread+0x1df/0x1400 kernel/workqueue.c:2279
>  kthread+0x343/0x4b0 kernel/kthread.c:240
>  ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:412
> 
> Allocated by task 2684:
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xa0/0xd0 mm/kasan/kasan.c:553
>  slab_post_alloc_hook mm/slab.h:444 [inline]
>  slab_alloc_node mm/slub.c:2741 [inline]
>  slab_alloc mm/slub.c:2749 [inline]
>  kmem_cache_alloc+0x105/0x330 mm/slub.c:2754
>  sk_prot_alloc+0x6a/0x2c0 net/core/sock.c:1468
>  sk_alloc+0xc9/0xbb0 net/core/sock.c:1528
>  __vsock_create+0xc8/0x9b0 [vsock]
>  vsock_create+0xfd/0x1a0 [vsock]
>  __sock_create+0x310/0x690 net/socket.c:1285
>  sock_create net/socket.c:1325 [inline]
>  __sys_socket+0x101/0x240 net/socket.c:1355
>  __do_sys_socket net/socket.c:1364 [inline]
>  __se_sys_socket net/socket.c:1362 [inline]
>  __x64_sys_socket+0x7d/0xd0 net/socket.c:1362
>  do_syscall_64+0x175/0x630 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Freed by task 2684:
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x130/0x180 mm/kasan/kasan.c:521
>  slab_free_hook mm/slub.c:1388 [inline]
>  slab_free_freelist_hook mm/slub.c:1415 [inline]
>  slab_free mm/slub.c:2988 [inline]
>  kmem_cache_free+0xce/0x410 mm/slub.c:3004
>  sk_prot_free net/core/sock.c:1509 [inline]
>  __sk_destruct+0x629/0x940 net/core/sock.c:1593
>  sk_destruct+0x4e/0x90 net/core/sock.c:1601
>  __sk_free+0xd3/0x320 net/core/sock.c:1612
>  sk_free+0x2a/0x30 net/core/sock.c:1623
>  __vsock_release+0x431/0x610 [vsock]
>  vsock_release+0x3c/0xc0 [vsock]
>  sock_release+0x91/0x200 net/socket.c:594
>  sock_close+0x17/0x20 net/socket.c:1149
>  __fput+0x368/0xa20 fs/file_table.c:209
>  task_work_run+0x1c5/0x2a0 kernel/task_work.c:113
>  exit_task_work include/linux/task_work.h:22 [inline]
>  do_exit+0x1876/0x26c0 kernel/exit.c:865
>  do_group_exit+0x159/0x3e0 kernel/exit.c:968
>  get_signal+0x65a/0x1780 kernel/signal.c:2482
>  do_signal+0xa4/0x1fe0 arch/x86/kernel/signal.c:810
>  exit_to_usermode_loop+0x1b8/0x260 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_64+0x505/0x630 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> The buggy address belongs to the object at ffff880026a3a600
>  which belongs to the cache AF_VSOCK of size 1056
> The buggy address is located 788 bytes inside of
>  1056-byte region [ffff880026a3a600, ffff880026a3aa20)
> The buggy address belongs to the page:
> page:ffffea00009a8e00 count:1 mapcount:0 mapping:0000000000000000 index:0x0 compound_mapcount: 0
> flags: 0xfffffc0008100(slab|head)
> raw: 000fffffc0008100 0000000000000000 0000000000000000 00000001000d000d
> raw: dead000000000100 dead000000000200 ffff880034471a40 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff880026a3a800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff880026a3a880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff880026a3a900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                          ^
>  ffff880026a3a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff880026a3aa00: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================

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