CVE-2023-52837

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

nbd: fix uaf in nbd_open

Commit 4af5f2e03013 (nbd: use blk_mq_alloc_disk and blk_cleanup_disk) cleans up disk by blk_cleanup_disk() and it wont set disk->private_data as NULL as before. UAF may be triggered in nbd_open() if someone tries to open nbd device right after nbd_put() since nbd has been free in nbd_dev_remove().

Fix this by implementing ->free_disk and free private data in it.

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/327462725b0f759f093788dfbcb2f1fd132f956b
• https://git.kernel.org/stable/c/4e9b3ec84dc97909876641dad14e0a2300d6c2a3
• https://git.kernel.org/stable/c/56bd7901b5e9dbc9112036ea615ebcba1565fafe
• https://git.kernel.org/stable/c/879947f4180bc6e83af64eb0515e0cf57fce15db
• https://git.kernel.org/stable/c/327462725b0f759f093788dfbcb2f1fd132f956b
• https://git.kernel.org/stable/c/4e9b3ec84dc97909876641dad14e0a2300d6c2a3
• https://git.kernel.org/stable/c/56bd7901b5e9dbc9112036ea615ebcba1565fafe
• https://git.kernel.org/stable/c/879947f4180bc6e83af64eb0515e0cf57fce15db