CVE-2025-71072 in Linux
Summary
by MITRE • 01/13/2026
In the Linux kernel, the following vulnerability has been resolved:
shmem: fix recovery on rename failures
maple_tree insertions can fail if we are seriously short on memory; simple_offset_rename() does not recover well if it runs into that. The same goes for simple_offset_rename_exchange().
Moreover, shmem_whiteout() expects that if it succeeds, the caller will progress to d_move(), i.e. that shmem_rename2() won't fail past the successful call of shmem_whiteout().
Not hard to fix, fortunately - mtree_store() can't fail if the index we are trying to store into is already present in the tree as a singleton.
For simple_offset_rename_exchange() that's enough - we just need to be careful about the order of operations.
For simple_offset_rename() solution is to preinsert the target into the tree for new_dir; the rest can be done without any potentially failing operations.
That preinsertion has to be done in shmem_rename2() rather than in simple_offset_rename() itself - otherwise we'd need to deal with the possibility of failure after successful shmem_whiteout().
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Analysis
by VulDB Data Team • 03/31/2026
The vulnerability identified as CVE-2025-71072 resides within the Linux kernel's shared memory implementation, specifically affecting the shmem subsystem's handling of file renaming operations. This issue manifests when the kernel attempts to rename shared memory files while under severe memory pressure conditions, creating a potential recovery failure scenario that could lead to inconsistent filesystem states. The flaw is particularly concerning as it impacts the fundamental file system operations that are critical for system stability and security. The vulnerability stems from inadequate error handling within the rename functionality, where the system fails to properly recover from memory allocation failures during maple tree insertions that occur during the rename process. This represents a classic case of insufficient resource management and error recovery mechanisms in kernel space operations, where the failure to properly handle memory exhaustion scenarios can lead to system instability or potential security implications.
The technical root cause of this vulnerability lies in the improper handling of maple tree insertion operations within the shmem subsystem's rename functions. When memory becomes critically scarce, the maple_tree insertions can fail, but the existing code does not adequately account for this failure mode in the simple_offset_rename() and simple_offset_rename_exchange() functions. The vulnerability specifically occurs when shmem_whiteout() successfully executes but the subsequent d_move() operation fails to complete properly, leaving the filesystem in an inconsistent state. This creates a scenario where the kernel's expectation of atomic operation completion is violated, as the system assumes that if shmem_whiteout() succeeds, the caller will automatically progress to d_move() without considering the possibility of failure at that stage. The issue is further compounded by the fact that the system does not properly validate the state of the maple tree operations before proceeding with subsequent steps, leading to potential data corruption or inconsistent filesystem metadata.
The operational impact of this vulnerability extends beyond simple system instability to potentially create security implications within shared memory environments. When memory pressure causes the maple tree insertions to fail, the rename operation becomes partially completed, leaving files in an inconsistent state that could be exploited by malicious actors. The vulnerability affects the reliability of shared memory filesystem operations, which are critical for inter-process communication and system performance. Attackers could potentially leverage this weakness to create denial-of-service conditions or manipulate shared memory mappings in ways that compromise system integrity. The flaw also impacts the kernel's ability to maintain consistent filesystem metadata, which could lead to data corruption or loss during concurrent file system operations. This vulnerability aligns with CWE-691, which addresses insufficient control flow management in kernel code, and represents a failure in proper error recovery mechanisms that should be implemented to maintain system stability under resource-constrained conditions.
The mitigation strategy for this vulnerability involves implementing proper preinsertion of target entries into the maple tree within the shmem_rename2() function rather than attempting these operations within the individual rename functions. This approach ensures that the critical tree insertion operations occur before any potentially failing operations, thereby preventing partial completion scenarios. The fix specifically requires that simple_offset_rename() preinsert the target into the tree for new_dir before proceeding with other operations, while simple_offset_rename_exchange() can be resolved through careful ordering of operations. The solution addresses the fundamental issue by ensuring that operations that cannot fail are completed first, eliminating the window where partial completion could occur. This approach aligns with ATT&CK technique T1490, which focuses on resource hijacking through manipulation of system resources, by ensuring proper resource management and preventing partial state transitions that could lead to system instability. The fix also incorporates best practices for kernel development by implementing defensive programming techniques that anticipate and handle resource exhaustion scenarios appropriately, thereby improving the overall robustness and security posture of the Linux kernel's shared memory subsystem.