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high 7.8

CVE-2024-53044 json

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

published last yr. modified 3mo ago also EUVD-2024-50460

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

In 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 ]

Patch / fix

  • Linux Linux 6.11.7, 6.12
  • linux Debian 14, Debian 13 6.11.7-1

debian advisories DEBIAN-CVE-2024-53044

  • linux Ubuntu 24.04 LTS 6.8.0-58.60
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1027.29
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1028.30
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1023.27
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1024.24
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1027.32
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1010.12
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1028.32

ubuntu advisories UBUNTU-CVE-2024-53044

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-570.12.1.el9_6
  • rv RHEL 9 5.14.0-570.12.1.el9_6
  • perf RHEL 9 5.14.0-570.12.1.el9_6
  • rtla RHEL 9 5.14.0-570.12.1.el9_6
  • libperf RHEL 9 5.14.0-570.12.1.el9_6
  • kernel-rt RHEL 9 5.14.0-570.12.1.el9_6
  • kernel-64k RHEL 9 5.14.0-570.12.1.el9_6
  • kernel-core RHEL 9 5.14.0-570.12.1.el9_6

red hat advisories RHSA-2025:6966

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2024-53044 updated cvss 5.5

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

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.12.1.el9_6, perf 5.14.0-570.12.1.el9_6, rtla 5.14.0-570.12.1.el9_6, python3-perf 5.14.0-570.12.1.el9_6, kernel-devel-matched 5.14.0-570.12.1.el9_6, kernel-64k-devel-matched 5.14.0-570.12.1.el9_6, +7 more Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.12.1.el9_6, kernel-64k 5.14.0-570.12.1.el9_6, kernel-core 5.14.0-570.12.1.el9_6, kernel-tools 5.14.0-570.12.1.el9_6, kernel-modules 5.14.0-570.12.1.el9_6, kernel-64k-core 5.14.0-570.12.1.el9_6, +27 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.12.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.12.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.12.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.12.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.12.1.el9_6 Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.12.1.el9_6, kernel-rt-64k 5.14.0-570.12.1.el9_6, kernel-rt-core 5.14.0-570.12.1.el9_6, kernel-rt-modules 5.14.0-570.12.1.el9_6, kernel-rt-64k-core 5.14.0-570.12.1.el9_6, kernel-rt-debug-core 5.14.0-570.12.1.el9_6, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.12.1.el9_6, kernel-rt-kvm 5.14.0-570.12.1.el9_6, kernel-rt-core 5.14.0-570.12.1.el9_6, kernel-rt-modules 5.14.0-570.12.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.12.1.el9_6, kernel-rt-debug-core 5.14.0-570.12.1.el9_6, +6 more
    fixed: vendor fix RHSA-2025:6966
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CISA ADP 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.