CVE-2025-21646 Information

Description

In the Linux kernel the following vulnerability has been resolved:

afs: Fix the maximum cell name length

The kafs filesystem limits the maximum length of a cell to 256 bytes but a problem occurs if someone actually does that: kafs tries to create a directory under /proc/net/afs/ with the name of the cell but that fails with a warning:

    WARNING: CPU: 0 PID: 9 at fs/proc/generic.c:405

because procfs limits the maximum filename length to 255.

However the DNS limits the maximum lookup length and by extension the maximum cell name to 255 less two (length count and trailing NUL).

Fix this by limiting the maximum acceptable cellname length to 253. This also allows us to be sure we can create the /afs/./\ mountpoint too.

Further split the YFS VL record cell name maximum to be the 256 allowed by the protocol and ignore the record retrieved by YFSVL.GetCellName if it exceeds 253.

Reference

https://git.kernel.org/stable/c/7673030efe0f8ca1056d3849d61784c6caa052af https://git.kernel.org/stable/c/7922b1f058fe24a93730511dd0ae2e1630920096 https://git.kernel.org/stable/c/8fd56ad6e7c90ac2bddb0741c6b248c8c5d56ac8 https://git.kernel.org/stable/c/aabe47cf5ac5e1db2ae0635f189d836f67024904