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, lets call sock_hold() only for a listening socket.

Found by InfoTeCS on behalf of Linux Verification Center (linuxtesting.org) with Syzkaller.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/0b9130247f3b6a1122478471ff0e014ea96bb735
• https://git.kernel.org/stable/c/280cf1173726a7059b628c610c71050d5c0b6937
• https://git.kernel.org/stable/c/5391f9db2cab5ef1cb411be1ab7dbec728078fba
• 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/d616876256b38ecf9a1a1c7d674192c5346bc69c
• https://git.kernel.org/stable/c/e07a9c2a850cdebf625e7a1b8171bd23a8554313