Bug 2460733 (CVE-2026-31438)

Summary: CVE-2026-31438 kernel: netfs: Fix kernel BUG in netfs_limit_iter() for ITER_KVEC iterators
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's netfs component. When a process crashes and the kernel attempts to write a core dump to a 9P filesystem, the `netfs_limit_iter()` function does not properly handle `ITER_KVEC` iterators. This oversight can lead to a kernel BUG, resulting in a system crash and a Denial of Service (DoS) for the affected system.
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Description OSIDB Bzimport 2026-04-22 15:08:05 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfs: Fix kernel BUG in netfs_limit_iter() for ITER_KVEC iterators

When a process crashes and the kernel writes a core dump to a 9P
filesystem, __kernel_write() creates an ITER_KVEC iterator. This
iterator reaches netfs_limit_iter() via netfs_unbuffered_write(), which
only handles ITER_FOLIOQ, ITER_BVEC and ITER_XARRAY iterator types,
hitting the BUG() for any other type.

Fix this by adding netfs_limit_kvec() following the same pattern as
netfs_limit_bvec(), since both kvec and bvec are simple segment arrays
with pointer and length fields. Dispatch it from netfs_limit_iter() when
the iterator type is ITER_KVEC.
Comment 1 Keith Grant 2026-04-22 17:00:53 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042243-CVE-2026-31438-66c2@gregkh/T