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Duoming Zhou 9fd75b66b8 ax25: Fix refcount leaks caused by ax25_cb_del() 
The previous commit d01ffb9eee ("ax25: add refcount in ax25_dev to
avoid UAF bugs") and commit feef318c85 ("ax25: fix UAF bugs of
net_device caused by rebinding operation") increase the refcounts of
ax25_dev and net_device in ax25_bind() and decrease the matching refcounts
in ax25_kill_by_device() in order to prevent UAF bugs, but there are
reference count leaks.

The root cause of refcount leaks is shown below:

     (Thread 1)                      |      (Thread 2)
ax25_bind()                          |
 ...                                 |
 ax25_addr_ax25dev()                 |
  ax25_dev_hold()   //(1)            |
  ...                                |
 dev_hold_track()   //(2)            |
 ...                                 | ax25_destroy_socket()
                                     |  ax25_cb_del()
                                     |   ...
                                     |   hlist_del_init() //(3)
                                     |
                                     |
     (Thread 3)                      |
ax25_kill_by_device()                |
 ...                                 |
 ax25_for_each(s, &ax25_list) {      |
  if (s->ax25_dev == ax25_dev) //(4) |
   ...                               |

Firstly, we use ax25_bind() to increase the refcount of ax25_dev in
position (1) and increase the refcount of net_device in position (2).
Then, we use ax25_cb_del() invoked by ax25_destroy_socket() to delete
ax25_cb in hlist in position (3) before calling ax25_kill_by_device().
Finally, the decrements of refcounts in ax25_kill_by_device() will not
be executed, because no s->ax25_dev equals to ax25_dev in position (4).

This patch adds decrements of refcounts in ax25_release() and use
lock_sock() to do synchronization. If refcounts decrease in ax25_release(),
the decrements of refcounts in ax25_kill_by_device() will not be
executed and vice versa.

Fixes: d01ffb9eee ("ax25: add refcount in ax25_dev to avoid UAF bugs")
Fixes: 87563a043c ("ax25: fix reference count leaks of ax25_dev")
Fixes: feef318c85 ("ax25: fix UAF bugs of net_device caused by rebinding operation")
Reported-by: Thomas Osterried <thomas@osterried.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2022-03-21 10:56:19 +00:00
Documentation ARM: SoC fixes for 5.17, part 3 2022-03-10 11:43:01 -08:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
arch - Free shmem backing storage for SGX enclave pages when those are 2022-03-13 10:36:38 -07:00
block block: fix blk_mq_attempt_bio_merge and rq_qos_throttle protection 2022-03-08 17:48:39 -07:00
certs certs: Fix build error when CONFIG_MODULE_SIG_KEY is empty 2022-01-23 00:08:44 +09:00
crypto crypto: af_alg - get rid of alg_memory_allocated 2022-02-15 14:29:04 +00:00
drivers ibmvnic: fix race between xmit and reset 2022-03-18 13:22:22 +00:00
fs ocfs2: fix crash when initialize filecheck kobj fails 2022-03-17 11:02:13 -07:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf 2022-03-18 10:33:47 +00:00
init lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() 2022-01-22 08:33:37 +02:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-04 09:25:05 -08:00
kernel configs/debug: restore DEBUG_INFO=y for overriding 2022-03-17 11:02:13 -07:00
lib ARM further fixes for 5.17-rc: 2022-03-02 16:11:56 -08:00
mm mm: swap: get rid of livelock in swapin readahead 2022-03-17 11:02:13 -07:00
net ax25: Fix refcount leaks caused by ax25_cb_del() 2022-03-21 10:56:19 +00:00
samples samples/seccomp: Adjust sample to also provide kill option 2022-02-10 19:09:12 -08:00
scripts kconfig: fix failing to generate auto.conf 2022-02-12 23:24:19 +09:00
security selinux/stable-5.17 PR 20220223 2022-02-23 17:19:55 -08:00
sound ALSA: intel_hdmi: Fix reference to PCM buffer address 2022-03-02 09:25:37 +01:00
tools selftest: net: Test IPv4 PMTU exceptions with DSCP and ECN 2022-03-18 14:06:45 -07:00
usr kbuild: remove include/linux/cyclades.h from header file check 2022-01-27 08:51:08 +01:00
virt KVM: Fix lockdep false negative during host resume 2022-02-17 09:52:50 -05:00
.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 MAINTAINERS: Update Jisheng's email address 2022-03-08 17:30:32 +01:00
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 Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2022-03-18 10:05:17 -07:00
Makefile Linux 5.17-rc8 2022-03-13 13:23:37 -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.