Bug 2395280 (CVE-2023-53171)

Summary: CVE-2023-53171 kernel: Linux kernel: Denial of Service in vfio/type1 due to locked_vm underflow
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel's vfio/type1 module. A local user could exploit this vulnerability when a vfio container is preserved across an `exec()` call. If the user unmaps a Direct Memory Access (DMA) mapping, the `locked_vm` counter can underflow. This underflow can cause subsequent DMA map requests to fail, leading to a Denial of Service (DoS) condition.
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Description OSIDB Bzimport 2025-09-15 15:04:59 UTC 
In the Linux kernel, the following vulnerability has been resolved:

vfio/type1: prevent underflow of locked_vm via exec()

When a vfio container is preserved across exec, the task does not change,
but it gets a new mm with locked_vm=0, and loses the count from existing
dma mappings.  If the user later unmaps a dma mapping, locked_vm underflows
to a large unsigned value, and a subsequent dma map request fails with
ENOMEM in __account_locked_vm.

To avoid underflow, grab and save the mm at the time a dma is mapped.
Use that mm when adjusting locked_vm, rather than re-acquiring the saved
task's mm, which may have changed.  If the saved mm is dead, do nothing.

locked_vm is incremented for existing mappings in a subsequent patch.
Comment 1 Keith Grant 2026-03-06 19:16:34 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025091554-CVE-2023-53171-be9f@gregkh/T