net/sched: sch_api: fix xa_insert() error path in tcf_block_get_ext()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2024-53044
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-11-19 18:15:24 UTC
Updated2026-08-04 11:21:45 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/sched: sch_api: fix xa_insert() error path in tcf_block_get_ext() This command: $ tc qdisc replace dev eth0 ingress_block 1 egress_block 1 clsact Error: block dev insert failed: -EBUSY. fails because user space requests the same block index to be set for both ingress and egress. [ side note, I don't think it even failed prior to commit 913b47d3424e ("net/sched: Introduce tc block netdev tracking infra"), because this is a command from an old set of notes of mine which used to work, but alas, I did not scientifically bisect this ] The problem is not that it fails, but rather, that the second time around, it fails differently (and irrecoverably): $ tc qdisc replace dev eth0 ingress_block 1 egress_block 1 clsact Error: dsa_core: Flow block cb is busy. [ another note: the extack is added by me for illustration purposes. the context of the problem is that clsact_init() obtains the same &q->ingress_block pointer as &q->egress_block, and since we call tcf_block_get_ext() on both of them, "dev" will be added to the block->ports xarray twice, thus failing the operation: once through the ingress block pointer, and once again through the egress block pointer. the problem itself is that when xa_insert() fails, we have emitted a FLOW_BLOCK_BIND command through ndo_setup_tc(), but the offload never sees a corresponding FLOW_BLOCK_UNBIND. ] Even correcting the bad user input, we still cannot recover: $ tc qdisc replace dev swp3 ingress_block 1 egress_block 2 clsact Error: dsa_core: Flow block cb is busy. Basically the only way to recover is to reboot the system, or unbind and rebind the net device driver. To fix the bug, we need to fill the correct error teardown path which was missed during code movement, and call tcf_block_offload_unbind() when xa_insert() fails. [ last note, fundamentally I blame the label naming convention in tcf_block_get_ext() for the bug. The labels should be named after what they do, not after the error path that jumps to them. This way, it is obviously wrong that two labels pointing to the same code mean something is wrong, and checking the code correctness at the goto site is also easier ]

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.002000000 probability, percentile 0.100770000 (date 2026-08-04)

Problem Types: NVD-CWE-noinfo | CWE-noinfo Not enough information

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1ADPDECLARED5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All
Operating System Linux Linux Kernel 6.12 rc1 All All
Operating System Linux Linux Kernel 6.12 rc2 All All
Operating System Linux Linux Kernel 6.12 rc3 All All
Operating System Linux Linux Kernel 6.12 rc4 All All
Operating System Linux Linux Kernel 6.12 rc5 All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 94e2557d086ad831027c54bc9c2130d337c72814 8966eb69a143b1c032365fe84f2815f3c46f2590 git Not specified
CNA Linux Linux affected 94e2557d086ad831027c54bc9c2130d337c72814 a13e690191eafc154b3f60afe9ce35aa9b9128b4 git Not specified
CNA Linux Linux affected 6.8 Not specified
CNA Linux Linux unaffected 6.8 semver Not specified
CNA Linux Linux unaffected 6.11.7 6.11.* semver Not specified
CNA Linux Linux unaffected 6.12 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a13e690191eafc154b3f60afe9ce35aa9b9128b4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/8966eb69a143b1c032365fe84f2815f3c46f2590 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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