Live › vulnerability › CVE-2026-98920
Go to dashboardIn the Linux kernel's netfs networking filesystem layer, allocations made directly through a mempool skip the allocation-tagging hook, causing kernel warnings with CONFIG_MEM_ALLOC_PROFILING_DEBUG enabled when reading files on a CIFS mount. The sources describe a correctness and debugging defect and do not describe an attacker gaining access or code execution.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.
Linux kernel builds with CONFIG_MEM_ALLOC_PROFILING_DEBUG enabled that use netfs, such as CIFS mounts, are the systems where the warning appears. The sources do not describe exploitation, and systems without that debug option are not described as affected.
No product ranges from the sources yet.
Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
In the Linux kernel, the following vulnerability has been resolved:
netfs: Fix missing alloc tagging of direct mempool allocations
Commit 1d78d56c43ef ("netfs: Fix folio_queue ENOMEM in writeback by adding a mempool") added a mempool for the folio_queues and made the request, subrequest and folio_queue allocations distinguish between writeback and everything else. Writeback is part of memory reclaim and must not fail due to ENOMEM, so it allocates under GFP_NOFS through mempool_alloc(), which may dip into the pool's reserve and, if that runs empty, wait for elements to be returned. The GFP_KERNEL paths, which can return -ENOMEM to their callers, invoke the pool's ->alloc() callback directly instead.
The direct call, however, skips the alloc_hooks() wrapper that the mempool_alloc() macro provides. The pool callbacks, mempool_alloc_slab() and mempool_kmalloc(), call kmem_cache_alloc_noprof() and kmalloc_noprof() and rely on current->alloc_tag having been set by the caller. With CONFIG_MEM_ALLOC_PROFILING_DEBUG=y this leads to
current->alloc_tag not set
WARNING: ./include/linux/alloc_tag.h:161 at __alloc_tagging_slab_alloc_hook
alloc_tag was not set
WARNING: ./include/linux/alloc_tag.h:166 at __alloc_tagging_slab_free_hook
at allocation and free time respectively, as reported when reading files on a CIFS mount. The allocations are also missing from /proc/allocinfo.
Wrap the direct ->alloc() invocations in alloc_hooks() with a new mempool_alloc_noreserve() helper in include/linux/mempool.h, next to the other alloc_hooks()-wrapped macros such as mempool_alloc(). The GFP_KERNEL paths keep their failable allocation semantics, they just get tagged now.
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