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Lin Ma b561275d63 mctp: defer the kfree of object mdev->addrs 
The function mctp_unregister() reclaims the device's relevant resource
when a netcard detaches. However, a running routine may be unaware of
this and cause the use-after-free of the mdev->addrs object.

The race condition can be demonstrated below

 cleanup thread               another thread
                          |
unregister_netdev()       |  mctp_sendmsg()
...                       |    ...
  mctp_unregister()       |    rt = mctp_route_lookup()
    ...                   |    mctl_local_output()
    kfree(mdev->addrs)    |      ...
                          |      saddr = rt->dev->addrs[0];
                          |

An attacker can adopt the (recent provided) mtcpserial driver with pty
to fake the device detaching and use the userfaultfd to increase the
race success chance (in mctp_sendmsg). The KASan report for such a POC
is shown below:

[   86.051955] ==================================================================
[   86.051955] BUG: KASAN: use-after-free in mctp_local_output+0x4e9/0xb7d
[   86.051955] Read of size 1 at addr ffff888005f298c0 by task poc/295
[   86.051955]
[   86.051955] Call Trace:
[   86.051955]  <TASK>
[   86.051955]  dump_stack_lvl+0x33/0x42
[   86.051955]  print_report.cold.13+0xb2/0x6b3
[   86.051955]  ? preempt_schedule_irq+0x57/0x80
[   86.051955]  ? mctp_local_output+0x4e9/0xb7d
[   86.051955]  kasan_report+0xa5/0x120
[   86.051955]  ? mctp_local_output+0x4e9/0xb7d
[   86.051955]  mctp_local_output+0x4e9/0xb7d
[   86.051955]  ? mctp_dev_set_key+0x79/0x79
[   86.051955]  ? copyin+0x38/0x50
[   86.051955]  ? _copy_from_iter+0x1b6/0xf20
[   86.051955]  ? sysvec_apic_timer_interrupt+0x97/0xb0
[   86.051955]  ? asm_sysvec_apic_timer_interrupt+0x12/0x20
[   86.051955]  ? mctp_local_output+0x1/0xb7d
[   86.051955]  mctp_sendmsg+0x64d/0xdb0
[   86.051955]  ? mctp_sk_close+0x20/0x20
[   86.051955]  ? __fget_light+0x2fd/0x4f0
[   86.051955]  ? mctp_sk_close+0x20/0x20
[   86.051955]  sock_sendmsg+0xdd/0x110
[   86.051955]  __sys_sendto+0x1cc/0x2a0
[   86.051955]  ? __ia32_sys_getpeername+0xa0/0xa0
[   86.051955]  ? new_sync_write+0x335/0x550
[   86.051955]  ? alloc_file+0x22f/0x500
[   86.051955]  ? __ip_do_redirect+0x820/0x1820
[   86.051955]  ? vfs_write+0x44d/0x7b0
[   86.051955]  ? vfs_write+0x44d/0x7b0
[   86.051955]  ? fput_many+0x15/0x120
[   86.051955]  ? ksys_write+0x155/0x1b0
[   86.051955]  ? __ia32_sys_read+0xa0/0xa0
[   86.051955]  __x64_sys_sendto+0xd8/0x1b0
[   86.051955]  ? exit_to_user_mode_prepare+0x2f/0x120
[   86.051955]  ? syscall_exit_to_user_mode+0x12/0x20
[   86.051955]  do_syscall_64+0x3a/0x80
[   86.051955]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[   86.051955] RIP: 0033:0x7f82118a56b3
[   86.051955] RSP: 002b:00007ffdb154b110 EFLAGS: 00000293 ORIG_RAX: 000000000000002c
[   86.051955] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f82118a56b3
[   86.051955] RDX: 0000000000000010 RSI: 00007f8211cd4000 RDI: 0000000000000007
[   86.051955] RBP: 00007ffdb154c1d0 R08: 00007ffdb154b164 R09: 000000000000000c
[   86.051955] R10: 0000000000000000 R11: 0000000000000293 R12: 000055d779800db0
[   86.051955] R13: 00007ffdb154c2b0 R14: 0000000000000000 R15: 0000000000000000
[   86.051955]  </TASK>
[   86.051955]
[   86.051955] Allocated by task 295:
[   86.051955]  kasan_save_stack+0x1c/0x40
[   86.051955]  __kasan_kmalloc+0x84/0xa0
[   86.051955]  mctp_rtm_newaddr+0x242/0x610
[   86.051955]  rtnetlink_rcv_msg+0x2fd/0x8b0
[   86.051955]  netlink_rcv_skb+0x11c/0x340
[   86.051955]  netlink_unicast+0x439/0x630
[   86.051955]  netlink_sendmsg+0x752/0xc00
[   86.051955]  sock_sendmsg+0xdd/0x110
[   86.051955]  __sys_sendto+0x1cc/0x2a0
[   86.051955]  __x64_sys_sendto+0xd8/0x1b0
[   86.051955]  do_syscall_64+0x3a/0x80
[   86.051955]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[   86.051955]
[   86.051955] Freed by task 301:
[   86.051955]  kasan_save_stack+0x1c/0x40
[   86.051955]  kasan_set_track+0x21/0x30
[   86.051955]  kasan_set_free_info+0x20/0x30
[   86.051955]  __kasan_slab_free+0x104/0x170
[   86.051955]  kfree+0x8c/0x290
[   86.051955]  mctp_dev_notify+0x161/0x2c0
[   86.051955]  raw_notifier_call_chain+0x8b/0xc0
[   86.051955]  unregister_netdevice_many+0x299/0x1180
[   86.051955]  unregister_netdevice_queue+0x210/0x2f0
[   86.051955]  unregister_netdev+0x13/0x20
[   86.051955]  mctp_serial_close+0x6d/0xa0
[   86.051955]  tty_ldisc_kill+0x31/0xa0
[   86.051955]  tty_ldisc_hangup+0x24f/0x560
[   86.051955]  __tty_hangup.part.28+0x2ce/0x6b0
[   86.051955]  tty_release+0x327/0xc70
[   86.051955]  __fput+0x1df/0x8b0
[   86.051955]  task_work_run+0xca/0x150
[   86.051955]  exit_to_user_mode_prepare+0x114/0x120
[   86.051955]  syscall_exit_to_user_mode+0x12/0x20
[   86.051955]  do_syscall_64+0x46/0x80
[   86.051955]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[   86.051955]
[   86.051955] The buggy address belongs to the object at ffff888005f298c0
[   86.051955]  which belongs to the cache kmalloc-8 of size 8
[   86.051955] The buggy address is located 0 bytes inside of
[   86.051955]  8-byte region [ffff888005f298c0, ffff888005f298c8)
[   86.051955]
[   86.051955] The buggy address belongs to the physical page:
[   86.051955] flags: 0x100000000000200(slab|node=0|zone=1)
[   86.051955] raw: 0100000000000200 dead000000000100 dead000000000122 ffff888005c42280
[   86.051955] raw: 0000000000000000 0000000080660066 00000001ffffffff 0000000000000000
[   86.051955] page dumped because: kasan: bad access detected
[   86.051955]
[   86.051955] Memory state around the buggy address:
[   86.051955]  ffff888005f29780: 00 fc fc fc fc 00 fc fc fc fc 00 fc fc fc fc 00
[   86.051955]  ffff888005f29800: fc fc fc fc 00 fc fc fc fc 00 fc fc fc fc 00 fc
[   86.051955] >ffff888005f29880: fc fc fc fb fc fc fc fc fa fc fc fc fc fa fc fc
[   86.051955]                                            ^
[   86.051955]  ffff888005f29900: fc fc 00 fc fc fc fc 00 fc fc fc fc 00 fc fc fc
[   86.051955]  ffff888005f29980: fc 00 fc fc fc fc 00 fc fc fc fc 00 fc fc fc fc
[   86.051955] ==================================================================

To this end, just like the commit e04480920d ("Bluetooth: defer
cleanup of resources in hci_unregister_dev()")  this patch defers the
destructive kfree(mdev->addrs) in mctp_unregister to the mctp_dev_put,
where the refcount of mdev is zero and the entire device is reclaimed.
This prevents the use-after-free because the sendmsg thread holds the
reference of mdev in the mctp_route object.

Fixes: 583be982d9 (mctp: Add device handling and netlink interface)
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Acked-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://lore.kernel.org/r/20220422114340.32346-1-linma@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2022-04-26 09:14:47 +02:00
arch Xtensa fixes for v5.18: 2022-04-20 12:43:27 -07:00
block block: don't print I/O error warning for dead disks 2022-04-15 06:33:03 -06:00
certs Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
crypto for-5.18/64bit-pi-2022-03-25 2022-03-26 12:01:35 -07:00
Documentation dt-bindings: net: dsa: realtek: cleanup compatible strings 2022-04-22 15:17:53 -07:00
drivers net: mscc: ocelot: don't add VID 0 to ocelot->vlans when leaving VLAN-aware bridge 2022-04-25 11:47:55 +01:00
fs Changes since last update: 2022-04-20 12:35:20 -07:00
include tcp: make sure treq->af_specific is initialized 2022-04-25 12:10:11 +01:00
init Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
ipc fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
kernel A small set of fixes for the timers core: 2022-04-17 09:53:01 -07:00
lib Driver core changes for 5.18-rc2 2022-04-10 09:55:09 -10:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP 2022-04-19 12:08:57 -07:00
net mctp: defer the kfree of object mdev->addrs 2022-04-26 09:14:47 +02:00
samples dma-mapping updates for Linux 5.18 2022-03-29 08:50:14 -07:00
scripts hardening fixes for v5.18-rc3 2022-04-12 14:29:40 -10:00
security hardening updates for v5.18-rc1-fix1 2022-03-31 11:43:01 -07:00
sound sound fixes for 5.18-rc3 2022-04-14 11:08:12 -07:00
tools wireguard: selftests: enable ACPI for SMP 2022-04-22 15:59:05 -07:00
usr Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
virt KVM/arm64 fixes for 5.18, take #1 2022-04-08 12:30:04 -04:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update Vasily Averin's email address 2022-04-08 14:20:36 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Networking fixes for 5.18-rc4, including fixes from xfrm and can. 2022-04-21 12:29:08 -07:00
Makefile Linux 5.18-rc3 2022-04-17 13:57:31 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.