sched: sch_cake: add bounds checks to host bulk flow fairness counts

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-21647
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-01-19 11:15:10 UTC
Updated2026-05-12 13:16:30 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: sched: sch_cake: add bounds checks to host bulk flow fairness counts Even though we fixed a logic error in the commit cited below, syzbot still managed to trigger an underflow of the per-host bulk flow counters, leading to an out of bounds memory access. To avoid any such logic errors causing out of bounds memory accesses, this commit factors out all accesses to the per-host bulk flow counters to a series of helpers that perform bounds-checking before any increments and decrements. This also has the benefit of improving readability by moving the conditional checks for the flow mode into these helpers, instead of having them spread out throughout the code (which was the cause of the original logic error). As part of this change, the flow quantum calculation is consolidated into a helper function, which means that the dithering applied to the ost load scaling is now applied both in the DRR rotation and when a sparse flow's quantum is first initiated. The only user-visible effect of this is that the maximum packet size that can be sent while a flow stays sparse will now vary with +/- one byte in some cases. This should not make a noticeable difference in practice, and thus it's not worth complicating the code to preserve the old behaviour.

Risk And Classification

Primary CVSS: v3.1 7.1 HIGH from [email protected]

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

Problem Types: CWE-125

CVSS v3.1 Breakdown

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

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 4a4eeefa514db570be025ab46d779af180e2c9bb 44fe1efb4961c1a5ccab16bb579dfc6b308ad58b git Not specified
CNA Linux Linux affected 7725152b54d295b7da5e34c2f419539b30d017bd b1a1743aaa4906c41c426eda97e2e2586f79246d git Not specified
CNA Linux Linux affected cde71a5677971f4f1b69b25e854891dbe78066a4 bb0245fa72b783cb23a9949c5048781341e91423 git Not specified
CNA Linux Linux affected 549e407569e08459d16122341d332cb508024094 a777e06dfc72bed73c05dcb437d7c27ad5f90f3f git Not specified
CNA Linux Linux affected d4a9039a7b3d8005b90c7b1a55a306444f0e5447 27202e2e8721c3b23831563c36ed5ac7818641ba git Not specified
CNA Linux Linux affected 546ea84d07e3e324644025e2aae2d12ea4c5896e 91bb18950b88f955838ec0c1d97f74d135756dc7 git Not specified
CNA Linux Linux affected 546ea84d07e3e324644025e2aae2d12ea4c5896e 737d4d91d35b5f7fa5bb442651472277318b0bfd git Not specified
CNA Linux Linux affected d7c01c0714c04431b5e18cf17a9ea68a553d1c3c git Not specified
CNA Linux Linux affected 6.11 Not specified
CNA Linux Linux unaffected 6.11 semver Not specified
CNA Linux Linux unaffected 5.4.291 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.235 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.179 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.125 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.72 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.10 6.12.* semver Not specified
CNA Linux Linux unaffected 6.13 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 TM MFP - BIOS affected * custom Not specified
ADP Siemens SIMATIC S7-1500 TM MFP - GNU/Linux Subsystem affected * custom Not specified

References

ReferenceSourceLinkTags
lists.debian.org/debian-lts-announce/2025/05/msg00030.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
cert-portal.siemens.com/productcert/html/ssa-503939.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/bb0245fa72b783cb23a9949c5048781341e91423 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-265688.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/b1a1743aaa4906c41c426eda97e2e2586f79246d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/91bb18950b88f955838ec0c1d97f74d135756dc7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/27202e2e8721c3b23831563c36ed5ac7818641ba 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/737d4d91d35b5f7fa5bb442651472277318b0bfd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/03/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/44fe1efb4961c1a5ccab16bb579dfc6b308ad58b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a777e06dfc72bed73c05dcb437d7c27ad5f90f3f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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