CVE-2024-44974

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

mptcp: pm: avoid possible UaF when selecting endp

select_local_address() and select_signal_address() both select an endpoint entry from the list inside an RCU protected section, but return a reference to it, to be read later on. If the entry is dereferenced after the RCU unlock, reading info could cause a Use-after-Free.

A simple solution is to copy the required info while inside the RCU protected section to avoid any risk of UaF later. The address ID might need to be modified later to handle the ID0 case later, so a copy seems OK to deal with.

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/0201d65d9806d287a00e0ba96f0321835631f63f
• https://git.kernel.org/stable/c/2b4f46f9503633dade75cb796dd1949d0e6581a1
• https://git.kernel.org/stable/c/48e50dcbcbaaf713d82bf2da5c16aeced94ad07d
• https://git.kernel.org/stable/c/9a9afbbc3fbfca4975eea4aa5b18556db5a0c0b8
• https://git.kernel.org/stable/c/ddee5b4b6a1cc03c1e9921cf34382e094c2009f1
• https://git.kernel.org/stable/c/f2c865e9e3ca44fc06b5f73b29a954775e4dbb38