CVE-2023-52760

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

gfs2: Fix slab-use-after-free in gfs2_qd_dealloc

In gfs2_put_super(), whether withdrawn or not, the quota should be cleaned up by gfs2_quota_cleanup().

Otherwise, struct gfs2_sbd will be freed before gfs2_qd_dealloc (rcu callback) has run for all gfs2_quota_data objects, resulting in use-after-free.

Also, gfs2_destroy_threads() and gfs2_quota_cleanup() is already called by gfs2_make_fs_ro(), so in gfs2_put_super(), after calling gfs2_make_fs_ro(), there is no need to call them again.

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/08a28272faa750d4357ea2cb48d2baefd778ea81
• https://git.kernel.org/stable/c/7ad4e0a4f61c57c3ca291ee010a9d677d0199fba
• https://git.kernel.org/stable/c/bdcb8aa434c6d36b5c215d02a9ef07551be25a37