CVE-2023-53790 in Linux
Summary
by MITRE • 12/09/2025
In the Linux kernel, the following vulnerability has been resolved:
bpf: Zeroing allocated object from slab in bpf memory allocator
Currently the freed element in bpf memory allocator may be immediately reused, for htab map the reuse will reinitialize special fields in map value (e.g., bpf_spin_lock), but lookup procedure may still access these special fields, and it may lead to hard-lockup as shown below:
NMI backtrace for cpu 16 CPU: 16 PID: 2574 Comm: htab.bin Tainted: G L 6.1.0+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), RIP: 0010:queued_spin_lock_slowpath+0x283/0x2c0 ...... Call Trace: <TASK> copy_map_value_locked+0xb7/0x170 bpf_map_copy_value+0x113/0x3c0 __sys_bpf+0x1c67/0x2780 __x64_sys_bpf+0x1c/0x20 do_syscall_64+0x30/0x60 entry_SYSCALL_64_after_hwframe+0x46/0xb0 ...... </TASK>
For htab map, just like the preallocated case, these is no need to initialize these special fields in map value again once these fields have been initialized. For preallocated htab map, these fields are initialized through __GFP_ZERO in bpf_map_area_alloc(), so do the similar thing for non-preallocated htab in bpf memory allocator. And there is no need to use __GFP_ZERO for per-cpu bpf memory allocator, because __alloc_percpu_gfp() does it implicitly.
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Analysis
by VulDB Data Team • 03/29/2026
The vulnerability described in CVE-2023-53790 resides within the linux kernel's bpf memory allocator subsystem, specifically affecting the handling of hash table (htab) map memory management. This issue represents a critical memory safety problem that can lead to system lockups and potential denial of service conditions. The flaw manifests when freed memory objects are immediately reallocated and reused without proper initialization of special fields within map values, creating a scenario where concurrent access patterns can trigger system instability.
The technical root cause of this vulnerability lies in the improper handling of memory allocation and deallocation cycles within the bpf subsystem's memory management. When hash table maps are used in bpf programs, certain special fields such as bpf_spin_lock must be properly initialized to maintain system stability. The current implementation fails to ensure that these fields are consistently initialized upon allocation, particularly in non-preallocated scenarios. This creates a race condition where a freed object may be immediately reallocated and accessed before proper initialization occurs, leading to undefined behavior and potential system crashes.
The operational impact of this vulnerability is severe and can result in system hard lockups as demonstrated in the provided NMI backtrace. The stack trace reveals that the issue occurs during a lookup procedure when accessing special fields that were not properly reinitialized after memory reuse. The kernel's queued_spin_lock_slowpath function becomes the point of failure, indicating that the spin lock mechanism has been corrupted due to improper memory state management. This vulnerability affects systems running kernel versions where the bpf subsystem is active and hash table maps are being utilized, potentially compromising system availability and stability.
The mitigation strategy involves modifying the bpf memory allocator to ensure proper initialization of special fields in map values, similar to how preallocated hash table maps handle this through __GFP_ZERO flag during allocation. This approach aligns with the principle of defensive programming and memory safety practices that are fundamental to kernel security. The fix specifically addresses the non-preallocated htab memory allocator by ensuring that memory allocations include zero-initialization of special fields, while maintaining the existing behavior for per-cpu allocators that already handle this implicitly through __alloc_percpu_gfp().
This vulnerability maps to CWE-457: Use of Uninitialized Variable and CWE-362: Concurrent Execution Using Shared Resource with Improper Synchronization, both of which are critical in kernel security contexts. The ATT&CK framework would categorize this under T1499.004: Endpoint Denial of Service, as it can lead to system lockups and service disruption. The issue demonstrates the importance of proper memory management in kernel space where uninitialized memory can lead to catastrophic system failures, emphasizing the need for comprehensive testing and validation of memory allocation patterns in security-critical subsystems.