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net/x25: Fix null-ptr-deref caused by x25_disconnect
Duoming Zhou authored 
[ Upstream commit 77816079 ]

When the link layer is terminating, x25->neighbour will be set to NULL
in x25_disconnect(). As a result, it could cause null-ptr-deref bugs in
x25_sendmsg(),x25_recvmsg() and x25_connect(). One of the bugs is
shown below.

    (Thread 1)                 |  (Thread 2)
x25_link_terminated()          | x25_recvmsg()
 x25_kill_by_neigh()           |  ...
  x25_disconnect()             |  lock_sock(sk)
   ...                         |  ...
   x25->neighbour = NULL //(1) |
   ...                         |  x25->neighbour->extended //(2)

The code sets NULL to x25->neighbour in position (1) and dereferences
x25->neighbour in position (2), which could cause null-ptr-deref bug.

This patch adds lock_sock() in x25_kill_by_neigh() in order to synchronize
with x25_sendmsg(), x25_recvmsg() and x25_connect(). What`s more, the
sock held by lock_sock() is not NULL, because it is extracted from x25_list
and u...
5c94b620
Name Last commit Last update
..
Kconfig Replace HTTP links with HTTPS ones: X.25 network layer
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license
af_x25.c net/x25: Fix null-ptr-deref caused by x25_disconnect
sysctl_net_x25.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license
x25_dev.c net/x25: Fix x25_neigh refcnt leak when receiving frame
x25_facilities.c treewide: Use fallthrough pseudo-keyword
x25_forward.c net: x25: convert to list_for_each_entry_safe()
x25_in.c treewide: Use fallthrough pseudo-keyword
x25_link.c net: x25: kerneldoc fixes
x25_out.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 41
x25_proc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 41
x25_route.c net: x25: kerneldoc fixes
x25_subr.c net/x25: Fix null-ptr-deref in x25_disconnect
x25_timer.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 41