CVE-2022-49411

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

bfq: Make sure bfqg for which we are queueing requests is online

Bios queued into BFQ IO scheduler can be associated with a cgroup that was already offlined. This may then cause insertion of this bfq_group into a service tree. But this bfq_group will get freed as soon as last bio associated with it is completed leading to use after free issues for service tree users. Fix the problem by making sure we always operate on online bfq_group. If the bfq_group associated with the bio is not online, we pick the first online parent.

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/075a53b78b815301f8d3dd1ee2cd99554e34f0dd
• https://git.kernel.org/stable/c/51f724bffa3403a5236597e6b75df7329c1ec6e9
• https://git.kernel.org/stable/c/6ee0868b0c3ccead5907685fcdcdd0c08dfe4b0b
• https://git.kernel.org/stable/c/7781c38552e6cc54ed8e9040279561340516b881
• https://git.kernel.org/stable/c/97bd6c56bdcb41079e488e31df56809e3b2ce628
• https://git.kernel.org/stable/c/ccddf8cd411c1800863ed357064e56ceffd356bb