Vulnerability CVE-2024-41006
Published: 2024-07-12

Description:
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

 References:
https://git.kernel.org/stable/c/d616876256b38ecf9a1a1c7d674192c5346bc69c
https://git.kernel.org/stable/c/e07a9c2a850cdebf625e7a1b8171bd23a8554313
https://git.kernel.org/stable/c/5391f9db2cab5ef1cb411be1ab7dbec728078fba
https://git.kernel.org/stable/c/280cf1173726a7059b628c610c71050d5c0b6937
https://git.kernel.org/stable/c/a02fd5d775cf9787ee7698c797e20f2fa13d2e2b
https://git.kernel.org/stable/c/b6ebe4fed73eedeb73f4540f8edc4871945474c8
https://git.kernel.org/stable/c/d377f5a28332954b19e373d36823e59830ab1712
https://git.kernel.org/stable/c/0b9130247f3b6a1122478471ff0e014ea96bb735
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