CVE-2026-92510 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
RDMA/core: Fix potential use after free in ib_destroy_srq_user()
When accessing a SRQ via the netlink path the only synchronization mechanism for the said SRQ is rdma_restrack_get(). Currently, rdma_restrack_del() is invoked at the end of ib_destroy_srq_user(), which is too late, since by that point vendor-specific resources associated with the SRQ might already be freed. This can leave a short window where the SRQ remains accessible through restrack, leading to a potential use-after-free.
Fix this by moving the rdma_restrack_begin_del() call to the start of ib_destroy_srq_user(), ensuring that the SRQ is removed from restrack before its internal resources are released. This guarantees that no new users hold references to a SRQ that is in the process of destruction.
In addition, this change preserves the intended inverted order between create and destroy routines: resources are added to restrack at the end of successful creation, and hence shall be removed from the restrack first thing during the destruction flow, which keeps the lifecycle management consistent and predictable.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel contains a vulnerability within the RDMA core subsystem specifically affecting the ib_destroy_srq_user function, where improper synchronization leads to a potential use-after-free condition. This flaw arises from an incorrect ordering of resource cleanup operations during the destruction phase of a Shared Receive Queue (SRQ). When an SRQ is accessed via the netlink path, the rdma_restrack_get mechanism serves as the primary synchronization primitive intended to manage references and prevent concurrent access issues. However, the existing implementation invokes rdma_restrack_del at the very end of the ib_destroy_srq_user routine. This late invocation creates a critical timing window where vendor-specific resources associated with the SRQ may already have been freed by internal cleanup processes, while the resource tracker still considers the SRQ active and accessible. Consequently, any subsequent access through the restrack mechanism can result in dereferencing memory that has already been released to the system, leading to undefined behavior, potential kernel crashes, or exploitation for arbitrary code execution if an attacker can trigger this race condition effectively.
The technical root cause lies in the mismatch between the lifecycle management of internal SRQ resources and their registration state within the resource tracker. By delaying the removal from restrack until after vendor-specific resources are freed, the system fails to enforce strict exclusion during the critical destruction window. This violates fundamental principles of safe memory management where an object must be logically removed from active tracking before its underlying storage is invalidated. The vulnerability aligns with CWE-416, Use After Free, as it involves accessing a pointer after that memory has been freed. Furthermore, this scenario can facilitate privilege escalation or denial of service attacks depending on the context in which the use-after-free occurs and whether an attacker can control the data written to the reclaimed memory region before it is reallocated for other purposes.
To mitigate this vulnerability, the fix involves restructuring the ib_destroy_srq_user function to call rdma_restrack_begin_del at the very beginning of the routine rather than at the end. This adjustment ensures that the SRQ is immediately removed from the resource tracker's active list before any internal resources are released or vendor-specific cleanup occurs. By doing so, no new users can acquire references to an SRQ that is currently being destroyed, effectively closing the race window and preventing access to freed memory. Additionally, this change preserves the intended inverted order between creation and destruction routines; since resources are added to restrack at the end of successful creation, they must be removed from restrack first during destruction to maintain consistent lifecycle management. This approach enhances predictability in resource handling and reduces complexity in synchronization logic.
From a defensive perspective, maintaining strict ordering in resource allocation and deallocation is crucial for kernel stability. The fix exemplifies best practices in systems programming by ensuring that logical state changes precede physical resource reclamation. Security practitioners should verify that their kernels are updated to include this patch from the RDMA core maintainers. Regular auditing of synchronization primitives and lifecycle management code paths can help identify similar vulnerabilities where race conditions might arise due to improper ordering of operations. Adhering to established standards such as those outlined in CWE-362, Concurrent Execution using Shared Resource with Improper Synchronization, further reinforces robustness against these types of concurrency-related flaws.