Kernel Patch Fixes QLogic Qla2xxx Double Free CVE-2024-26930

A small, surgical change in the Linux kernel’s QLogic SCSI driver has closed a potentially serious memory-handling bug: a double-free of the ha->vp_map pointer in the qla2xxx driver that could cause kernel memory corruption and denial-of-service, and — in the worst case — open paths that attackers might chain toward privilege escalation.

Background / Overview​

The qla2xxx family of drivers implements support for QLogic Fibre Channel host bus adapters (HBAs) and is widely used on servers that attach to SAN storage. During a static analysis sweep (Coverity), the code that manages per-adapter mappings (the driver’s ha->vp_map pointer) was flagged for a lifecycle bug: code paths could free the same pointer twice. The upstream maintainers accepted a minimal, defensive fix that ensures a freed pointer is nulled so subsequent free operations are harmless.
This defect is tracked as CVE-2024-26930. Vendor and public vulnerability databases record the issue as a double free (CWE‑415) that was patched upstream in the stable kernel trees and subsequently incorporated into distribution kernels and vendor errata.

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What exactly was wrong?​

The bug, simply explained​

At its core the problem was a classic pointer-lifetime error in the driver’s memory allocation and cleanup paths. The driver allocated memory for ha->vp_map and, under certain error or teardown paths, freed that buffer in one function and then attempted to free it again in a shared cleanup routine. A double free like this can:

• corrupt kernel heap metadata,
• cause immediate kernel panics (loss of availability), or
• under specific and often complex conditions, be leveraged to change allocator state and eventually lead to arbitrary code execution with kernel privileges.

Upstream developers chose the conventional defensive correction: after freeing the buffer, set the pointer to NULL so repeat frees are safe (kfree(NULL) is a no-op). That change eliminates the window where the pointer could be freed twice.

Where in the driver it lived​

The problem touches two logical places in the qla2xxx codebase:

• The allocation / initialization path (the code that creates and populates ha->vp_map).
• The common free/teardown routine qla2x00_mem_free(ha), which is called in multiple exit paths.

When the allocation path itself triggered an error or invoked early cleanup after a partial allocation, the code freed ha->vp_map and later fell through to qla2x00_mem_free(ha), which freed that memory again. The patch forces the code to null the pointer immediately after the first free.

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Scope and affected versions​

Determining "who is affected" requires two checks: the upstream kernel versions that contained the vulnerable code, and the distribution kernels / vendor updates that either included the fix or provide backports.

• Upstream stable kernels received the fix in the early May 2024 maintenance window; stable-tree commits and downstream advisories indicate that kernel series such as 6.6.x, 6.7.x and 6.8.x were updated with backported fixes in the point releases that followed (for example, 6.6.24, 6.7.12 and 6.8.3 were mentioned in public advisories as containing the patch).
• Distribution and vendor advisories list the issue under their own advisories and errata. Oracle Linux published ELSA/errata and recommended kernel upgrades; Red Hat, SUSE and other enterprise distributors likewise published advisories and backports. If you run a vendor-supplied kernel, apply the vendor-provided update for your platform rather than relying on upstream version numbers.
• Third-party vulnerability aggregators that scan fixed-version metadata map the vulnerable windows to ranges between the minor version releases: for example, some reports list affected ranges as kernels after 6.7 up to but not including 6.7.12, and after 6.8 up to but not including 6.8.3 — meaning those point releases close the window. This kind of range information is useful, but you should corroborate it against your distribution’s kernel package metadata.

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Impact and exploitability​

Availability-first impact (DoS)​

The immediate and easiest-to-achieve impact of a double free in kernel space is denial of service. A double free commonly corrupts heap metadata and promptly triggers a kernel panic or oops, resulting in a host reboot or halted services. That means storage servers or any host using affected HBAs could see sustained or persistent loss of availability while the attack is delivered or — in repeated-exploit scenarios — experience service outage after repeated triggers. This maps to a high availability impact even when confidentiality and integrity remain intact.

Privilege escalation or code execution — possible, but not trivial​

Security advisories and analysts note that double frees can, under clever heap-manipulation and timing conditions, be escalated into memory corruption primitives that permit arbitrary kernel-memory writes or control of allocator-linked lists. That, in turn, can be used for privilege escalation and arbitrary code execution at kernel level. However, reliably exploiting such conditions in modern kernels is non-trivial and often architecture- and allocator-dependent.
Public feeds and vendor notes flag the maximum theoretical impact as severe (including potential RCE), but they also emphasize the local attack vector: an attacker needs some level of local access or an ability to trigger the relevant driver code path; remote, unauthenticated exploitation is not the expected attack vector. In short: high impact is possible; exploitation requires favorable conditions and local access.

CVSS and disagreement between sources​

Different sources have published different base scores and vectors. NVD initially recorded the advisory without a final CVSS score at the time of publication; some vendors calculated a moderate base score (for example Oracle’s advisory listed a CVSS v3 score of 5.5 with an AV:L vector), while independent aggregators assigned higher scores in their systems (some public trackers cite higher values such as 7.8). The variance reflects differing risk models (local vs. authenticated access required, definite DoS vs. speculative RCE) — and underlines the need to evaluate risk in your environment, not just rely on a single numeric score.

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The upstream fix — what changed in the code​

The upstream patch is intentionally small and defensive: after the code calls kfree(ha->vp_map), it sets ha->vp_map to NULL. Because the kernel routine kfree() is safe when passed NULL, subsequent calls to kfree(ha->vp_map) become no-ops and no double free occurs. This is the canonical and lowest-risk fix for this particular class of bug.
Why that is a sensible change:

• It is minimal and easy to audit.
• It avoids introducing new allocator logic or complex refcounting in a high-frequency path.
• It preserves the driver’s existing teardown semantics while removing the double-free window.

The same change pattern — freeing followed immediately by pointer nulling — is a common defensive idiom across kernel codebases.

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Vendor and distribution responses​

Major Linux distributors and vendors issued advisories and errata promptly after the upstream patch:

• Oracle Linux published an ELSA entry and listed the fix in kernel errata; their advisory documents the kernel package versions that include the patch for Oracle customers.
• Red Hat, SUSE and other enterprise OS providers tracked and backported the fix into affected kernels and listed remediation guidance in their advisories. Aggregators and vulnerability databases consolidated vendor advisories and offered recommended upgrade paths.

If your systems run vendor-supplied kernels (RHEL, SLES, Oracle Linux, Ubuntu LTS, etc.), apply the vendor-supplied update that corresponds to your platform and kernel ABI rather than attempting to infer fixes from upstream version numbers.

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Detection, mitigation and remediation guidance for administrators​

Below are practical, prioritized steps for operators and security teams responsible for storage- or SAN-attached hosts.

• Immediate mitigation (short term)
• If your environment does not use QLogic Fibre Channel HBAs or the qla2xxx driver, consider unloading or blacklisting the module until you can apply a kernel update. This action reduces exposure quickly but requires understanding dependencies (some distributions embed the driver in their initramfs or build it into the kernel).
• Restrict local access to hosts that present qla2xxx devices. The vulnerability requires local invocation of driver code paths; limiting who can log into machines reduces practical exploit avenues.
• Apply vendor updates (recommended remediation)
• Identify the kernel package and exact version used on each host (use uname -r and distribution package tools).
• Check your vendor’s advisory for the exact fixed kernel package name and version.
• Apply the vendor-supplied kernel update and reboot hosts as required.
• For rolling-kernel environments (custom-built kernels), apply the upstream patch or cherry-pick the fix into your build tree, rebuild and deploy consistently across the fleet.
• Alternative mitigations (if updates are temporarily impossible)
• If livepatching is available in your environment, check whether your vendor offers a livepatch for this specific kernel package — vendors sometimes issue livepatches for critical fixes when reboots are particularly disruptive.
• Limit exposure by removing local unprivileged access, tightening sudo rules, and ensuring only trusted administrators can trigger hardware or driver actions that touch qla2xxx paths.
• Detection and monitoring
• Look for kernel oopses or storage-related panics in system logs and dmesg on hosts with qla2xxx modules loaded. Double-frees often present as heap corruption, oops traces, or immediate reboots.
• Monitor vendor telemetry or security feeds for evidence of in-the-wild exploitation attempts targeting qla2xxx; as of the latest consolidated advisories there was no widely publicized in-the-wild exploit kit for CVE‑2024‑26930, but DoS-triggering reproducers can exist in proof-of-concept form.

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Risk analysis and operational recommendation​

Strengths of the upstream response​

• The fix is minimal and surgical: it addresses the root cause without introducing new complexity.
• Upstream maintainers incorporated the correction quickly into stable branches; vendors published errata and backports in short order.

Residual risks​

• Even with a simple fix, kernel-space memory-corruption bugs deserve careful scrutiny. Double frees are a class of bug that have historically been escalated in chained exploits, particularly against older allocators or when combined with other memory-priming techniques.
• The real-world risk varies by environment: servers that expose local access to many users, or service appliances that run untrusted workloads that can interact with SCSI/HBA paths, are at relatively higher operational risk compared with hardened single-tenant hosts.

Recommendation (practical, prioritized)​

• Treat CVE‑2024‑26930 as operationally important if you run qla2xxx on production hosts, because the primary impact is availability and the potential for worse outcomes exists.
• Apply vendor kernel updates as soon as practical and test them in staging before broad rollout.
• If you cannot update immediately, implement mitigations (module blacklist, reduce local access, restrict service accounts) and monitor logs for kernel oopses.
• Where possible, incorporate the patch into your configuration management so you can demonstrate a consistent, auditable remediation posture across the estate.

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Developer / code-auditor notes (for kernel maintainers and driver authors)​

• This vulnerability is a clear example of how resource cleanup paths can diverge and cause double-free windows. When a resource is freed in multiple places, always ensure ownership semantics are explicit: either adopt a single owner or neutralize pointers after free by assigning NULL or using clear owner flags.
• Unit tests and static analysis tools (Coverity, KUnit-style tests, or syzbot fuzzing) proved their worth by surfacing this problem; instrumenting driver teardown paths with KASAN during development can catch lifecycle errors early.
• When applying small fixes in stable trees, prefer the minimal defensive pattern (free+null) rather than extensive refactors — provided the change is validated and doesn’t mask deeper ownership problems.

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Community reaction and context​

Community threads and kernel-security discussion noted the fix was small but important; operators with QLogic HBAs were advised to check their distribution’s errata. Those community posts and threads echoed the common advice: patch, or if impossible, reduce attack surface by unloading or blacklisting the qla2xxx module until remediation is possible.

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Final verdict​

CVE‑2024‑26930 is a textbook kernel memory-lifecycle bug: a double-free in a widely used SCSI driver that can produce immediate availability impacts and — under complex exploitation scenarios — be leveraged into more severe compromises. The fix is straightforward and has been merged upstream and distributed in vendor kernels. The operational action required is likewise straightforward: identify affected hosts, apply vendor-provided kernel updates (or upstream patches if you maintain custom kernels), and, where updates cannot be applied immediately, reduce exposure by restricting local access or unloading the driver.
Treat this as an availability-focused high-priority item for hosts that use QLogic HBAs. Patching removes the risk quickly; the path from discovery to remediation was short and surgical, reflecting a healthy upstream-vendor patch pipeline. For administrators: patch, test, and restore normal operations — and treat similar lifecycle bugs as signals to extend testing to teardown and error paths in driver code.

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Source: MSRC Security Update Guide - Microsoft Security Response Center