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CVE-2025-21647 Detail

Description

In 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.


Metrics

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CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

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Hyperlink Resource
https://git.kernel.org/stable/c/27202e2e8721c3b23831563c36ed5ac7818641ba
https://git.kernel.org/stable/c/737d4d91d35b5f7fa5bb442651472277318b0bfd
https://git.kernel.org/stable/c/91bb18950b88f955838ec0c1d97f74d135756dc7
https://git.kernel.org/stable/c/a777e06dfc72bed73c05dcb437d7c27ad5f90f3f

Weakness Enumeration

CWE-ID CWE Name Source

Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2025-21647
NVD Published Date:
01/19/2025
NVD Last Modified:
01/19/2025
Source:
kernel.org