CVE-2025-37867 in Linux
Summary
by MITRE • 05/09/2025
In the Linux kernel, the following vulnerability has been resolved:
RDMA/core: Silence oversized kvmalloc() warning
syzkaller triggered an oversized kvmalloc() warning. Silence it by adding __GFP_NOWARN.
syzkaller log: WARNING: CPU: 7 PID: 518 at mm/util.c:665 __kvmalloc_node_noprof+0x175/0x180 CPU: 7 UID: 0 PID: 518 Comm: c_repro Not tainted 6.11.0-rc6+ #6 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:__kvmalloc_node_noprof+0x175/0x180 RSP: 0018:ffffc90001e67c10 EFLAGS: 00010246 RAX: 0000000000000100 RBX: 0000000000000400 RCX: ffffffff8149d46b RDX: 0000000000000000 RSI: ffff8881030fae80 RDI: 0000000000000002 RBP: 000000712c800000 R08: 0000000000000100 R09: 0000000000000000 R10: ffffc90001e67c10 R11: 0030ae0601000000 R12: 0000000000000000 R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000000 FS: 00007fde79159740(0000) GS:ffff88813bdc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000180 CR3: 0000000105eb4005 CR4: 00000000003706b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ib_umem_odp_get+0x1f6/0x390 mlx5_ib_reg_user_mr+0x1e8/0x450 ib_uverbs_reg_mr+0x28b/0x440 ib_uverbs_write+0x7d3/0xa30 vfs_write+0x1ac/0x6c0 ksys_write+0x134/0x170 ? __sanitizer_cov_trace_pc+0x1c/0x50 do_syscall_64+0x50/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e
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Analysis
by VulDB Data Team • 01/31/2026
The vulnerability described in CVE-2025-37867 relates to a warning condition within the Linux kernel's RDMA/core subsystem that was triggered by syzkaller, a fuzzing tool designed to identify kernel-level issues. This specific instance involves an oversized kvmalloc() warning, which occurs when the kernel attempts to allocate memory using the kvmalloc function with a size that exceeds expectations. The warning mechanism in question is part of the kernel's memory management subsystem and is intended to alert developers to potential issues such as excessive memory allocations that could lead to system instability or resource exhaustion. The issue manifests during operations involving InfiniBand user memory registration, specifically when processing user-space memory regions through the mlx5_ib_reg_user_mr function, which is part of the Mellanox ConnectX driver for RDMA (Remote Direct Memory Access) operations.
The technical flaw lies in how the kernel handles memory allocation warnings when dealing with large memory blocks, particularly in the context of RDMA operations. The ib_umem_odp_get function, which manages user memory regions for on-demand paging, calls kvmalloc with parameters that trigger a warning in the kernel's memory management utilities. The warning originates from mm/util.c at line 665 in the __kvmalloc_node_noprof function, indicating that the allocation size being requested is outside the expected range for normal operation. This particular warning was not an indication of a functional failure but rather a noise mechanism that could potentially mask more serious issues or create false positives in system monitoring. The kernel developers identified that this warning was being generated in legitimate use cases and decided to suppress it to avoid unnecessary log spamming while maintaining system stability.
The operational impact of this vulnerability is primarily related to system logging noise and potential monitoring interference rather than direct system instability or security breaches. When syzkaller or similar tools perform memory allocation tests, the excessive warnings could clutter system logs, making it difficult to identify genuine issues or security events. This could impact system administrators and security analysts who rely on clean log outputs for monitoring and incident response activities. The suppression of these warnings through the addition of __GFP_NOWARN flag ensures that legitimate RDMA operations, particularly those involving large memory regions, do not generate false positive alerts. This change aligns with the kernel's approach to managing false positives in memory allocation warnings, particularly in performance-critical subsystems like RDMA where large allocations are expected during normal operation. The vulnerability does not represent a direct threat to system security but rather an operational concern that affects system observability and monitoring practices.
Mitigation for this vulnerability involves applying the kernel patch that adds the __GFP_NOWARN flag to the kvmalloc() call within the RDMA/core subsystem. This approach follows established kernel development practices for handling legitimate but noisy warnings in performance-critical subsystems. The patch represents a targeted fix that addresses the specific warning condition without altering core memory management behavior or introducing new security risks. System administrators should ensure they are running kernel versions that include this fix, particularly in environments where RDMA operations are common or where systems are monitored using automated tools that might be affected by excessive logging. The fix aligns with the ATT&CK framework's concept of privilege escalation through system-level modifications, where operational changes to kernel behavior can impact system stability and monitoring. From a CWE perspective, this vulnerability relates to CWE-704, which deals with incorrect type conversion or incorrect type usage in memory management, though the actual impact is more about logging behavior than fundamental type handling issues. The solution demonstrates a common pattern in kernel development where false positive warnings are suppressed in well-understood operational contexts to maintain system clarity without compromising security or functionality.