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linux-stable/drivers/net/hamradio
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Lin Ma b2f37aead1 hamradio: improve the incomplete fix to avoid NPD 
The previous commit 3e0588c291 ("hamradio: defer ax25 kfree after
unregister_netdev") reorder the kfree operations and unregister_netdev
operation to prevent UAF.

This commit improves the previous one by also deferring the nullify of
the ax->tty pointer. Otherwise, a NULL pointer dereference bug occurs.
Partial of the stack trace is shown below.

BUG: kernel NULL pointer dereference, address: 0000000000000538
RIP: 0010:ax_xmit+0x1f9/0x400
...
Call Trace:
 dev_hard_start_xmit+0xec/0x320
 sch_direct_xmit+0xea/0x240
 __qdisc_run+0x166/0x5c0
 __dev_queue_xmit+0x2c7/0xaf0
 ax25_std_establish_data_link+0x59/0x60
 ax25_connect+0x3a0/0x500
 ? security_socket_connect+0x2b/0x40
 __sys_connect+0x96/0xc0
 ? __hrtimer_init+0xc0/0xc0
 ? common_nsleep+0x2e/0x50
 ? switch_fpu_return+0x139/0x1a0
 __x64_sys_connect+0x11/0x20
 do_syscall_64+0x33/0x40
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The crash point is shown as below

static void ax_encaps(...) {
  ...
  set_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags); // ax->tty = NULL!
  ...
}

By placing the nullify action after the unregister_netdev, the ax->tty
pointer won't be assigned as NULL net_device framework layer is well
synchronized.

Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2021-12-18 12:32:48 +00:00
..
6pack.c hamradio: remove needs_free_netdev to avoid UAF 2021-11-12 19:56:47 -08:00
Kconfig dmascc: add CONFIG_VIRT_TO_BUS dependency 2021-09-28 13:12:07 +01:00
Makefile
…
baycom_epp.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-10-22 11:41:16 +01:00
baycom_par.c hamradio: use ndo_siocdevprivate 2021-07-27 20:11:44 +01:00
baycom_ser_fdx.c hamradio: use ndo_siocdevprivate 2021-07-27 20:11:44 +01:00
baycom_ser_hdx.c hamradio: use ndo_siocdevprivate 2021-07-27 20:11:44 +01:00
bpqether.c hamradio: use dev_addr_set() for setting device address 2021-10-13 09:41:37 -07:00
dmascc.c hamradio: use dev_addr_set() for setting device address 2021-10-13 09:41:37 -07:00
hdlcdrv.c hamradio: use dev_addr_set() for setting device address 2021-10-13 09:41:37 -07:00
mkiss.c hamradio: improve the incomplete fix to avoid NPD 2021-12-18 12:32:48 +00:00
scc.c hamradio: use dev_addr_set() for setting device address 2021-10-13 09:41:37 -07:00
yam.c hamradio: use dev_addr_set() for setting device address 2021-10-13 09:41:37 -07:00
z8530.h
…