CVE-2025-40039 — linux / linux_kernel
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')In the Linux kernel, the following vulnerability has been resolved:
ksmbd: Fix race condition in RPC handle list access
The 'sess->rpc_handle_list' XArray manages RPC handles within a ksmbd session. Access to this list is intended to be protected by 'sess->rpc_lock' (an rw_semaphore). However, the locking implementation was flawed, leading to potential race conditions.
In ksmbd_session_rpc_open(), the code incorrectly acquired only a read lock before calling xa_store() and xa_erase(). Since these operations modify the XArray structure, a write lock is required to ensure exclusive access and prevent data corruption from concurrent modifications.
Furthermore, ksmbd_session_rpc_method() accessed the list using xa_load() without holding any lock at all. This could lead to reading inconsistent data or a potential use-after-free if an entry is concurrently removed and the pointer is dereferenced.
Fix these issues by:
- Using down_write() and up_write() in ksmbd_session_rpc_open() to ensure exclusive access during XArray modification, and ensuring the lock is correctly released on error paths.
- Adding down_read() and up_read() in ksmbd_session_rpc_method() to safely protect the lookup.
| Software | From | Fixed in |
|---|---|---|
| linux / linux_kernel | 5.15.145 | 5.16 |
| linux / linux_kernel | 6.1.71 | 6.2 |
| linux / linux_kernel | 6.3 | 6.6.123 |
| linux / linux_kernel | 6.7 | 6.12.53 |
| linux / linux_kernel | 6.13 | 6.17.3 |
- https://git.kernel.org/stable/c/305853cce379407090a73b38c5de5ba748893aee
- https://git.kernel.org/stable/c/5cc679ba0f4505936124cd4179ba66bb0a4bd9f3
- https://git.kernel.org/stable/c/69674b029002b1d90b655f014bdf64f404efa54d
- https://git.kernel.org/stable/c/6b615a8fb3af0baf8126cde3d4fee97d57222ffc
- https://git.kernel.org/stable/c/6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1
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A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
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