CVE-2021-47459

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

can: j1939: j1939_netdev_start(): fix UAF for rx_kref of j1939_priv

It will trigger UAF for rx_kref of j1939_priv as following.

    cpu0                                    cpu1

j1939_sk_bind(socket0, ndev0, …) j1939_netdev_start j1939_sk_bind(socket1, ndev0, …) j1939_netdev_start j1939_priv_set j1939_priv_get_by_ndev_locked j1939_jsk_add ….. j1939_netdev_stop kref_put_lock(&priv->rx_kref, …) kref_get(&priv->rx_kref, …) REFCOUNT_WARN(addition on 0;…)

==================================================== refcount_t: addition on 0; use-after-free. WARNING: CPU: 1 PID: 20874 at lib/refcount.c:25 refcount_warn_saturate+0x169/0x1e0 RIP: 0010:refcount_warn_saturate+0x169/0x1e0 Call Trace: j1939_netdev_start+0x68b/0x920 j1939_sk_bind+0x426/0xeb0 ? security_socket_bind+0x83/0xb0

The rx_krefs kref_get() and kref_put() should use j1939_netdev_lock to protect.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/6e8811707e2df0c6ba920f0cad3a3bca7b42132f
• https://git.kernel.org/stable/c/864e77771a24c877aaf53aee019f78619cbcd668
• https://git.kernel.org/stable/c/a0e47d2833b4f65e6c799f28c6b636d36b8b936d
• https://git.kernel.org/stable/c/d9d52a3ebd284882f5562c88e55991add5d01586
• https://git.kernel.org/stable/c/6e8811707e2df0c6ba920f0cad3a3bca7b42132f
• https://git.kernel.org/stable/c/864e77771a24c877aaf53aee019f78619cbcd668
• https://git.kernel.org/stable/c/a0e47d2833b4f65e6c799f28c6b636d36b8b936d
• https://git.kernel.org/stable/c/d9d52a3ebd284882f5562c88e55991add5d01586