CVE-2023-52483

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

mctp: perform route lookups under a RCU read-side lock

Our current route lookups (mctp_route_lookup and mctp_route_lookup_null) traverse the nets route list without the RCU read lock held. This means the route lookup is subject to preemption, resulting in an potential grace period expiry, and so an eventual kfree() while we still have the route pointer.

Add the proper read-side critical section locks around the route lookups, preventing premption and a possible parallel kfree.

The remaining net->mctp.routes accesses are already under a rcu_read_lock, or protected by the RTNL for updates.

Based on an analysis from Sili Luo rootlab@huawei.com, where introducing a delay in the route lookup could cause a UAF on simultaneous sendmsg() and route deletion.

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/1db0724a01b558feb1ecae551782add1951a114a
• https://git.kernel.org/stable/c/2405f64a95a7a094eb24cba9bcfaffd1ea264de4
• https://git.kernel.org/stable/c/5093bbfc10ab6636b32728e35813cbd79feb063c
• https://git.kernel.org/stable/c/6c52b12159049046483fdb0c411a0a1869c41a67
• https://git.kernel.org/stable/c/1db0724a01b558feb1ecae551782add1951a114a
• https://git.kernel.org/stable/c/2405f64a95a7a094eb24cba9bcfaffd1ea264de4
• https://git.kernel.org/stable/c/5093bbfc10ab6636b32728e35813cbd79feb063c
• https://git.kernel.org/stable/c/6c52b12159049046483fdb0c411a0a1869c41a67