Title: kernel de Linux
Description: En el kernel de Linux se ha resuelto la siguiente vulnerabilidad: hamradio: mejora la solución incompleta para evitar NPD. El commit anterior 3e0588c291d6 ("hamradio: defer ax25 kfree after unregister_netdev") reordena las operaciones kfree y unregister_netdev para prevenir UAF. Esta confirmación mejora la anterior al diferir también la anulación del puntero ax->tty. De lo contrario, se produce un error de desreferencia del puntero NULL. A continuación se muestra parte del seguimiento de la pila. ERROR: desreferencia del puntero NULL del kernel, dirección: 0000000000000538 RIP: 0010:ax_xmit+0x1f9/0x400... Seguimiento de llamadas: dev_hard_start_xmit+0xec/0x320 sch_direct_xmit+0xea/0x240 __qdisc_run+0x166/0x5c0 __dev_queue_x mit+0x2c7/0xaf0 ax25_std_establecer_data_link+0x59/0x60 ax25_connect+0x3a0/0x500? seguridad_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 El punto de bloqueo se muestra a continuación static void ax_encaps(...) { ... set_bit(TTY_DO_WRITE_WAKEUP, &ax-> tty->banderas ); // hacha->tty = NULL! ... } Al colocar la acción de anulación después de unregister_netdev, el puntero ax->tty no se asignará ya que la capa de marco NULL net_device está bien sincronizada.

In the Linux kernel, the following vulnerability has been resolved:

hamradio: improve the incomplete fix to avoid NPD

The previous commit 3e0588c291d6 ("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.

Rejected reason: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.

kernel.org https://git.kernel.org/stable/c/03d00f7f1815ec00dab5035851b3de83afd054a8

kernel.org https://git.kernel.org/stable/c/371a874ea06f147d6ca30be43dad33683965eba6

kernel.org https://git.kernel.org/stable/c/7dd52af1eb5798f590d9d9e1c56ed8f5744ee0ca

kernel.org https://git.kernel.org/stable/c/83ba6ec97c74fb1a60f7779a26b6a94b28741d8a

kernel.org https://git.kernel.org/stable/c/a5c6a13e9056d87805ba3042c208fbd4164ad22b

kernel.org https://git.kernel.org/stable/c/a7b0ae2cc486fcb601f9f9d87d98138cc7b7f7f9

kernel.org https://git.kernel.org/stable/c/b2f37aead1b82a770c48b5d583f35ec22aabb61e

kernel.org https://git.kernel.org/stable/c/b68f41c6320b2b7fbb54a95f07a69f3dc7e56c59