CVE-2022-50484
Description
A memory leak was found in the Linux kernel's USB audio driver in the synchronization endpoint URB allocation path. When memory allocation fails partway through allocating URBs for a sync endpoint, the error handling code fails to release the partially allocated URBs because the endpoint's URB counter hasn't been updated yet. This leaves allocated URBs orphaned in memory, leading to resource exhaustion and denial of service with repeated failures.
Statement
USB audio devices often use isochronous endpoints for audio streaming, with separate synchronization endpoints for clock recovery. During initialization, the driver allocates multiple URBs (USB Request Blocks) for these endpoints. The allocation happens in a loop: create URB, allocate buffer, repeat. The ep->nurbs field tracks how many URBs have been successfully allocated. Here's the problem: ep->nurbs is only set after the entire loop completes successfully. If allocation fails midway—say, the driver successfully allocates 5 URBs but fails on the 6th due to -ENOMEM—the error handler is supposed to clean up. It loops from 0 to ep->nurbs, freeing each URB. But since ep->nurbs is still zero (it was never updated), the loop doesn't execute at all. The 5 successfully allocated URBs are simply abandoned. Each time USB audio initialization fails under memory pressure, more URBs leak. The fix is simple: set ep->nurbs before starting the loop, so the cleanup knows how far to iterate.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
An adversary that can cause a resource counter to become inaccurate may be able to create situations where resources are not accounted for and not released, thus causing resources to become scarce for future needs.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An adversary that can cause a resource counter to become inaccurate may be able to force an error that causes the product to crash or exit out of its current operation.
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