CVE-2024-36001

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

netfs: Fix the pre-flush when appending to a file in writethrough mode

In netfs_perform_write(), when the file is marked NETFS_ICTX_WRITETHROUGH

or O_*SYNC or RWF_*SYNC was specified, write-through caching is performed

on a buffered file. When setting up for write-through, we flush any

conflicting writes in the region and wait for the write to complete,

failing if there's a write error to return.

The issue arises if we're writing at or above the EOF position because we

skip the flush and - more importantly - the wait. This becomes a problem

if there's a partial folio at the end of the file that is being written out

and we want to make a write to it too. Both the already-running write and

the write we start both want to clear the writeback mark, but whoever is

second causes a warning looking something like:

------------[ cut here ]------------

R=00000012: folio 11 is not under writeback

WARNING: CPU:

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References