A newly disclosed Linux kernel vulnerability in the RDMA/siw stack — tracked as CVE‑2024‑57857 — can cause a kernel-mode use‑after‑free (KASAN slab-use-after-free) in siw_query_port, producing a hard availability failure and forcing reboots or kernel oopses on affected systems; operators must treat this as a high‑priority stability/availability risk for hosts that expose RDMA, multi‑tenant services, or software that can exercise siw/ib_device lifecycles, and should apply upstream or vendor patches immediately or use careful mitigations until updates are deployed.
Background / Overview
The Linux kernel's SoftiWARP (siw) RDMA transport provides a software implementation of the iWARP protocol for remote direct memory access (RDMA) over TCP. In this case, a code path in the siw driver maintained a per‑device direct link to the kernel's net_device object in addition to relying on the associated ib_device/net_device management. That redundant, locally managed pointer could become stale and be referenced after the underlying net_device had been freed, triggering a KASAN-detected slab-use-after-free during a siw_query_port invocation. The upstream remedy removes the direct per‑device link and relies on the canonical ib_device net_device management to avoid double‑management and the resulting lifecycle mismatch. This is primarily an availability vulnerability: a successful trigger of the use‑after‑free manifests as a kernel oops or crash, which in multi‑tenant or infrastructure hosts can translate to service outages, VM failures, or cascading operational impact. Public vulnerability trackers and distribution advisories classify the weakness as a use‑after‑free (CWE‑416) with a CVSS v3 score commonly reported around 7.8 (High), although vendor scoring and contextual severity differ. There is, at disclosure, no authoritative public proof‑of‑concept demonstrating remote, unauthenticated RCE or privilege escalation purely from this defect. Nevertheless, availability faults in kernel code are operationally severe and deserve rapid remediation.What changed in the kernel (technical summary)
- The vulnerable code maintained a local pointer/link to a net_device per siw device instance rather than fully deferring to the ib_device-managed net_device linkage.
- Under certain device lifecycle sequences (for example: network interface reconfiguration, device removal, or racey queries via siw_query_port, the local pointer could reference memory that had already been freed.
- The use‑after‑free was detected by KASAN as a slab-use-after-free during siw_query_port calls, producing an immediate kernel oops and potentially reboot/host crash.
- Upstream fixes remove the redundant direct link and ensure siw relies on the canonical ib_device net_device relationship, closing the lifecycle gap and eliminating the stale pointer risk. The fix was merged into the stable kernel trees and has been backported into distribution kernel packages. The upstream stable commits associated with the fix are listed in public advisories and OSV/patch trackers.
Affected versions and exposure model
Affected trees / versions (summary)
- Kernel versions compiled with the in‑tree siw driver in the range from historical inclusion up through versions prior to the stable fix are impacted; public trackers list broadly vulnerable ranges such as 5.3 ≤ kernel < 6.12.9 and certain 6.13 release candidates. Distribution CVE pages give package‑level details for which releases remain vulnerable or are already fixed. Operators must consult their distribution/security tracker to map the CVE → packaged kernel version for their environment.
Attack vector and prerequisites
- Attack vector: Local (AV:L). An attacker or a misbehaving local process/container/tenant must be able to interact with the siw/ib_device paths or influence device lifecycle events (for example, network interface rebinds, device removal, or query calls).
- Privileges required: Low in many practical environments. Because the triggering operations can be exercised by user‑level workloads that cause certain network or RDMA control flows, multi‑tenant hosts and CI/build nodes are higher risk.
- Remote exploitation: There is no authoritative public evidence of remote, unauthenticated RCE caused directly by this CVE. Nevertheless, a kernel use‑after‑free is a severe primitive and — in theory — could be part of more complex exploit chains, so defenders should not treat absence of PoC as lack of danger.
Detection and hunting guidance
Quick checks to determine whether systems are likely exposed:- Confirm whether the kernel includes the siw module or compiled driver:
- lsmod | grep -i siw
- modinfo siw (returns module path and version if present)
- Check running kernel versions and package changelogs:
- uname -r
- For Debian/Ubuntu: apt changelog linux-image-$(uname -r) or check your distribution security tracker for the package → CVE mapping.
- For RHEL/SUSE/Oracle: consult vendor advisories and rpm -q --changelog kernel‑package.
- Look for KASAN and siw-related oops traces in kernel logs:
- journalctl -k --no-pager | egrep -i 'KASAN|siw_query_port|use-after-free|slab-use-after-free'
- dmesg | egrep -i 'siw|KASAN|slab-use-after-free|oops'
- If you run centralized log aggregation, add short‑term rules to flag:
- "KASAN: slab-use-after-free" messages
- Backtraces that contain siw_query_port or siw device symbols
Remediation: immediate and long-term actions
Highest‑priority action (definitive fix)
- Identify systems that run kernels containing the vulnerable siw implementation.
- Install vendor or distribution kernel packages that explicitly list CVE‑2024‑57857 (or include the upstream stable commit IDs) and reboot into the updated kernel. Vendors have published package advisories across Ubuntu, Debian, SUSE, and others — confirm mapping in your distro tracker.
Short‑term mitigations if immediate patching is impossible
- Blacklist the siw driver (only where RDMA/siw is not needed):
- Create a file: /etc/modprobe.d/blacklist‑siw.conf
- Add the line: blacklist siw
- Update initramfs if needed and reboot.
- Caveat: blacklisting siw disables software iWARP RDMA functionality. Evaluate service impact and vendor drivers that may implement RDMA in other ways before blacklisting.
- Restrict who may bind/manipulate RDMA/ib_devices:
- Harden udev rules and restrict unprivileged users from performing device rebinds or manipulations that could exercise siw lifecycles.
- For container hosts, avoid running untrusted workloads that can create or control RDMA devices on the host; schedule packet-processing or RDMA test workloads to patched nodes.
- Isolate affected appliances and vendor images:
- For embedded devices or appliances with vendor kernels that have not received backports, isolate those devices on segmented networks or remove them from critical production paths until vendor updates are available.
- Capture diagnostic evidence proactively:
- Enable kernel crash collection (kdump/vmcore) and centralized logging so that if an oops occurs you retain the forensics without rebooting into the problem. This improves triage and supports vendor engagement.
How to verify a patch or backport is present
- Check your distribution's security advisory or package changelog for an explicit reference to CVE‑2024‑57857 or the upstream stable commit IDs (distributors generally include commit IDs or a changelog note).
- If you build kernels in-house, search your kernel sources for the upstream commit(s) or for changes in siw device net_device handling and the removal of the per‑device net_device link.
- After patch and reboot, validate:
- Run the same workloads that previously caused siw queries or device reconfigures and confirm no KASAN oops traces appear.
- Monitor kernel logs for at least several days to ensure no reappearance of siw_query_port‑related traces.
Operational playbook (concise checklist)
- Inventory
- Enumerate hosts with RDMA/siw drivers: lsmod | grep -i siw
- Identify hosts running multi‑tenant workloads, shared CI runners, or packet processing services.
- Map package → patch
- Use distro security tracker pages (Ubuntu, Debian, SUSE, etc. to find which kernel package versions contain the fix and whether any vendor backports are available.
- Pilot
- Patch a small canary group with representative RDMA and network workloads, reboot, and validate.
- Broad rollout
- Stage updates across the fleet with rollback plans and monitoring for regressions.
- Post‑patch validation
- Confirm absence of KASAN oopses and verify system stability under representative load.
- Vendor engagement
- For appliances and embedded devices: open tickets with vendors if backports are delayed and insist on a fixed image or kernel patch.
Risk analysis — strengths and residual concerns
Strengths of the upstream response
- The upstream fix is surgical: it removes a redundant lifecycle pointer rather than redesigning the whole transport stack, minimizing regression risk and easing backporting into stable kernels.
- Multiple independent distribution and CVE trackers have ingested the fix and mapped it into kernel packages — enabling operators to rely on standard vendor patch channels.
Residual risks and operational caveats
- Vendor/OEM lag: Embedded appliances and vendor‑forked kernels can remain unpatched for long periods. These systems form the long tail of risk and may require isolation or replacement.
- Local vector in multi‑tenant contexts: In cloud or shared infrastructures, the “local” attack vector equates to guest/tenant adjacencies; untrusted tenants could trigger the condition and disrupt co‑tenants.
- Potential for chaining: Although no public PoC of RCE exists for this CVE at disclosure, memory‑safety bugs in kernel space can sometimes be combined with other primitives to achieve more serious outcomes; treat that theoretical possibility as a reason to patch promptly.
Practical commands & examples
Detection and inventory- Check kernel and module:
- uname -r
- lsmod | grep -i siw
- modinfo siw
- Search for KASAN/siw traces:
- sudo journalctl -k --no-pager | egrep -i 'KASAN|siw_query_port|slab-use-after-free'
- sudo dmesg | egrep -i 'siw|KASAN|slab-use-after-free|oops'
- Debian/Ubuntu:
- apt changelog linux-image-$(uname -r) | egrep -i 'CVE-2024-57857|siw'
- or check the Ubuntu CVE advisory page for CVE‑2024‑57857.
- echo 'blacklist siw' | sudo tee /etc/modprobe.d/blacklist‑siw.conf
- sudo update-initramfs -u
- Reboot
Windows‑admin considerations (WSL / Linux guests)
Windows administrators running Linux workloads under WSL2, Hyper‑V, or guest VMs should be aware that container image updates do not fix host‑kernel vulnerabilities. If the vulnerable kernel is used by a WSL2 distribution or a Linux guest managed by Windows, consult the guest image or WSL kernel update path and apply the updated kernel images per vendor guidance. For WSL2 users, check whether the shipped WSL kernel binary has been updated by Microsoft or whether the guest distro provides kernel package updates, and apply as directed. Centralized patching and verification remain critical because host kernel fixes are required to address this class of bug.Contrasting vendor scoring and practical prioritization
Different vendor trackers show variation in CVSS scoring and patch availability. For example, some platform trackers show Medium severity while others list CVSS v3 = 7.8 (High). These numeric differences arise from vendor assumptions about attack context (local vs multi‑tenant exposure), expected privilege of the attacker, and operational impact models. Operators should prioritize remediation based on real exposure and impact in their environments: hosts running RDMA/siw under multi‑tenant conditions, cloud hypervisors, high‑availability storage nodes, or nodes that host critical services should be patched immediately regardless of numeric score.Unverifiable or uncertain claims — flagged
- Public in‑the‑wild exploitation: At disclosure time, there is no authoritative public evidence of active exploitation or a public proof‑of‑concept that converts this defect into a reliable remote code‑execution chain. This absence should not be treated as proof of safety; adversaries with local access or cloud‑tenant positions could weaponize the defect for denial‑of‑service. This claim is verified against public trackers and NVD/OSV entries, which do not report active exploitation at disclosure.
- Exact commit IDs and patch details on git.kernel.org: Upstream stable commit pages are referenced by advisories (listed in OSV and distro trackers), but direct git.kernel.org access may be blocked by tooling or network restrictions in some automated fetchers. Operators should rely on vendor package changelogs or direct kernel source trees when direct upstream links are not accessible. When in doubt, match package changelog entries to the upstream commit IDs provided in advisories.
Conclusion
CVE‑2024‑57857 is a classic kernel lifecycle bug: a redundant local pointer to net_device in RDMA/siw produced a use‑after‑free that surfaces as a KASAN slab‑use‑after‑free in siw_query_port. Although it is not a published RCE vector, the immediate risk is severe for availability — kernel oopses and host crashes in production environments. The fix is small and conservative, has been merged into stable kernel trees, and is being distributed by OS vendors; the operational imperative is clear: inventory hosts, apply vendor kernel updates that include the fix, and reboot in staged waves. Where immediate patching is impossible, apply compensating controls (blacklist siw if safe, restrict device lifecycle operations, isolate affected appliances) and enable kernel crash capture to preserve forensic evidence. Given the potential for multi‑tenant disruption and the long tail of vendor‑forked kernels, this is a high‑value fix to apply quickly as part of routine kernel patch management.Source: MSRC Security Update Guide - Microsoft Security Response Center
