CVE-2024-41006

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

netrom: Fix a memory leak in nr_heartbeat_expiry()

syzbot reported a memory leak in nr_create() [0].

Commit 409db27e3a2e ("netrom: Fix use-after-free of a listening socket.")

added sock_hold() to the nr_heartbeat_expiry() function, where

a) a socket has a SOCK_DESTROY flag or

b) a listening socket has a SOCK_DEAD flag.

But in the case "a," when the SOCK_DESTROY flag is set, the file descriptor

has already been closed and the nr_release() function has been called.

So it makes no sense to hold the reference count because no one will

call another nr_destroy_socket() and put it as in the case "b."

nr_connect

nr_establish_data_link

nr_start_heartbeat

nr_release

switch (nr->state)

case NR_STATE_3

nr->state = NR_STATE_2

sock_set_flag(sk, SOCK_DESTROY);

nr_rx_frame

nr_process_rx_frame

switch (nr->state)

case NR_STATE_2

nr_state2_machine()

nr_disconnect()

nr_sk(sk)->state = NR_STATE_0

sock_set_flag(sk, SOCK_DEAD)

nr_heartbeat_expiry

switch (nr->state)

case NR_STATE_0

if (sock_flag(sk, SOCK_DESTROY) ||

(sk->sk_state == TCP_LISTEN

&& sock_flag(sk, SOCK_DEAD)))

sock_hold() // ( !!! )

nr_destroy_socket()

To fix the memory leak, let's call sock_hold() only for a listening socket.

Found by InfoTeCS on behalf of Linux Verification Center

(linuxtesting.org) with Syzkaller.

[0]: https://syzkaller.appspot.com/bug?extid=d327a1f3b12e1e206c16