net/sched: Handle TC_ACT_REDIRECT from qdisc filter chains

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-68441
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-12 00:17:44 UTC
Updated2026-08-12 00:17:44 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/sched: Handle TC_ACT_REDIRECT from qdisc filter chains When a TC filter attached to a qdisc filter chain returns TC_ACT_REDIRECT (ex: via an eBPF program calling bpf_redirect() or an act_bpf action), the redirect was silently lost i.e no qdisc classify function handled TC_ACT_REDIRECT, so the packet fell through the switch and was enqueued normally instead of being redirected. This has been broken since bpf_redirect() was introduced for TC in commit 27b29f63058d ("bpf: add bpf_redirect() helper"). We got lucky for a long time because bpf_net_context was a per-CPU variable that was always available. commit 401cb7dae813 ("net: Reference bpf_redirect_info via task_struct on PREEMPT_RT.") turned bpf_net_context into a task_struct member that is only set up by explicit callers. Without a caller setting it up, bpf_redirect() itself crashes with a NULL pointer dereference in bpf_net_ctx_get_ri(). However, even with bpf_net_context available, TC_ACT_REDIRECT from qdisc filter chains cannot be honored without adding skb_do_redirect() calls to every qdisc classify function, which would require changes across net/sched/. Isolate it to ebpf core where it belongs. Instead, add a tcf_classify_qdisc() inline helper in pkt_cls.h, as a wrapper around tcf_classify() for use by qdisc classify functions and tcf_qevent_handle(). When the classify verdict is TC_ACT_REDIRECT, the wrapper converts it to TC_ACT_SHOT, dropping the packet rather than letting it continue silently. Dropping is preferred over letting the packet through because the user immediately sees packet loss. Silently passing the packet through would hide the problem and leave the user wondering why their redirect is not working. The clsact fast path, tc_run() continues to call tcf_classify() directly and is unaffected: TC_ACT_REDIRECT is returned as-is and handled by sch_handle_egress/ingress() calling skb_do_redirect() as before.

Risk And Classification

EPSS: 0.001480000 probability, percentile 0.045380000 (date 2026-08-12)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 27b29f63058d26c6c1742f1993338280d5a41dc6 c8fd74445e86f88096d2f6cf0f9e4d54d8ed1781 git Not specified
CNA Linux Linux affected 27b29f63058d26c6c1742f1993338280d5a41dc6 ec48b3be2c8595dd290be883dbd4fb8b2f9f5d5e git Not specified
CNA Linux Linux affected 4.4 Not specified
CNA Linux Linux unaffected 4.4 semver Not specified
CNA Linux Linux unaffected 7.1.6 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc5 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/c8fd74445e86f88096d2f6cf0f9e4d54d8ed1781 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ec48b3be2c8595dd290be883dbd4fb8b2f9f5d5e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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