CVE-2022-49080

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

mm/mempolicy: fix mpol_new leak in shared_policy_replace

If mpol_new is allocated but not used in restart loop, mpol_new will be freed via mpol_put before returning to the caller. But refcnt is not initialized yet, so mpol_put could not do the right things and might leak the unused mpol_new. This would happen if mempolicy was updated on the shared shmem file while the sp->lock has been dropped during the memory allocation.

This issue could be triggered easily with the below code snippet if there are many processes doing the below work at the same time:

shmid = shmget((key_t)5566, 1024 * PAGE_SIZE, 0666|IPC_CREAT); shm = shmat(shmid, 0, 0); loop many times { mbind(shm, 1024 * PAGE_SIZE, MPOL_LOCAL, mask, maxnode, 0); mbind(shm + 128 * PAGE_SIZE, 128 * PAGE_SIZE, MPOL_DEFAULT, mask, maxnode, 0); }

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

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/198932a14aeb19a15cf19e51e151d023bc4cd648
• https://git.kernel.org/stable/c/25f506273b6ae806fd46bfcb6fdaa5b9ec81a05b
• https://git.kernel.org/stable/c/39a32f3c06f6d68a530bf9612afa19f50f12e93d
• https://git.kernel.org/stable/c/4ad099559b00ac01c3726e5c95dc3108ef47d03e
• https://git.kernel.org/stable/c/5e16dc5378abd749a836daa9ee4ab2c8d2668999
• https://git.kernel.org/stable/c/6e00309ac716fa8225f0cbde2cd9c24f0e74ee21
• https://git.kernel.org/stable/c/8510c2346d9e47a72b7f018a36ef0c39483e53d6
• https://git.kernel.org/stable/c/f7e183b0a7136b6dc9c7b9b2a85a608a8feba894
• https://git.kernel.org/stable/c/fe39ac59dbbf893b73b24e3184161d0bd06d6651