Description

In the Linux kernel, the following vulnerability has been resolved: md/raid5-ppl: fix use-after-free in ppl_do_flush() The loop in ppl_do_flush() continues iterating after calling ppl_io_unit_finished(), touching io->pending_flushes and leading to a use-after-free. Add a break statement to stop the loop once io is freed.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-09-24T16:17:22.927Z",
  "pubdate": "2026-09-24T16:17:22.927Z",
  "executiveSummary": "A critical use-after-free (UAF) vulnerability exists in the Linux kernel's md/raid5-ppl component, specifically within the ppl_do_flush() function.\nThe vulnerability arises from improper memory management during the processing of raid5 persistent write-log (PPL) flushes.\nAn attacker capable of triggering specific I/O operations can exploit this flaw to induce a use-after-free condition, which may lead to system instability, kernel panics, or potential arbitrary code execution.\nThe affected component resides in the md (Multiple Device) driver, which is integral to software RAID implementations in the Linux kernel.\nExploitation requires the ability to interact with the MD device interface, typically necessitating local user access with appropriate privileges to manage or trigger RAID array operations.\nThe primary risk is a denial-of-service (DoS) via kernel crash, though sophisticated attackers could theoretically leverage the memory corruption for privilege escalation depending on the environment and slab layout.",
  "technicalDetails": "The vulnerability is located in the ppl_do_flush() function within the Linux kernel's md/raid5-ppl subsystem. The root cause is a logic error in the iteration cycle used to process pending PPL (Persistent Write Log) I/O units.\nDuring the flushing process, the kernel iterates through a list of pending I/O units to commit log updates. Within this loop, the function calls ppl_io_unit_finished(io), which performs the necessary cleanup and frees the memory associated with the specific io structure. However, the loop logic fails to terminate after this operation. Instead, it proceeds to continue iterating, subsequently accessing the now-freed io structure via the io->pending_flushes member.\nThis sequence results in a classic use-after-free (UAF) condition. By the time the loop attempts to read or modify io->pending_flushes, the memory previously occupied by the io object has been released back to the kernel slab allocator. If the allocator has re-allocated this memory to a different object, the kernel will perform operations on unintended data, leading to memory corruption.\nThe attack flow entails an attacker triggering I/O operations that force the RAID5 module to enter a PPL flush state. Since this process is internal to the kernel's handling of RAID arrays, the vulnerability is reachable through any interface that allows a user to initiate or influence MD device I/O, such as write requests to a device managed by a RAID5 array utilizing the PPL feature.\nFrom an exploitation perspective, once the UAF occurs, the behavior is nondeterministic and depends heavily on the kernel's memory state. If the freed memory is reused, an attacker might be able to overwrite sensitive kernel pointers or control structures. While the primary immediate impact is a kernel panic (Denial of Service), the possibility of memory corruption allows for potential escalation of privileges if the attacker can influence the slab allocator to fill the freed slot with a structure containing function pointers or security-critical data.\nThis vulnerability affects versions of the Linux kernel where PPL support is active in the raid5 module and the flush logic has not been corrected with the necessary loop termination control flow."
}