CVE-2026-92512 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
RDMA/core: Fix use after free in ib_query_qp()
When querying a QP via the netlink flow the only synchronization mechanism for the said QP is rdma_restrack_get(), meanwhile during the QP destroy path rdma_restrack_del() is called at the end of the ib_destroy_qp_user() function which is too late, since by then the vendor specific resources for said QP would already be destroyed, and till the rdma_restrack_del() is called this QP can still be accessed, which could cause the use after free below.
Fix this by moving the rdma_restrack_begin_del() to the start of the ib_destroy_qp_user(), which in turn waits for all usages of the QP to be done then removes it from the database to prevent access to it while it is being destroyed.
RIP: 0010:ib_query_qp+0x15/0x50 [ib_core]
Code: 48 83 05 5d 8e b9 ff 01 eb b5 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 c7 46 40 00 00 00 00 48 c7 46 78 00 00 00 00 <48> 8b 07 48 8b 80 88 01 00 00 48 85 c0 74 1a 48 83 05 54 91 b9 ff RSP: 0018:ff11000108a8f2f0 EFLAGS: 00010202 RAX: 0000000000000000 RBX: ff11000108a8f370 RCX: ff11000108a8f370 RDX: 0000000000000000 RSI: ff11000108a8f3d8 RDI: 0000000000000000 RBP: ff1100010de5a000 R08: 0000000000000e80 R09: 0000000000000004 R10: ff110001057a604c R11: 0000000000000000 R12: ff11000108a8f370 R13: ff110001090e8000 R14: 0000000000000000 R15: ff110001057a602c FS: 00007f2ffd8db6c0(0000) GS:ff110008dc90b000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000010b9a7004 CR4: 0000000000373eb0 Call Trace: <TASK> mlx5_ib_gsi_query_qp+0x21/0x50 [mlx5_ib]
mlx5_ib_query_qp+0x689/0x9d0 [mlx5_ib]
ib_query_qp+0x35/0x50 [ib_core]
fill_res_qp_entry_query.isra.0+0x47/0x280 [ib_core]
? __wake_up+0x40/0x50 ? netlink_broadcast_filtered+0x15a/0x550 ? kobject_uevent_env+0x562/0x710 ? ep_poll_callback+0x242/0x270 ? __nla_put+0xc/0x20 ? nla_put+0x28/0x40 ? nla_put_string+0x2e/0x40 [ib_core]
fill_res_qp_entry+0x138/0x190 [ib_core]
res_get_common_dumpit+0x4a5/0x800 [ib_core]
? fill_res_qp_entry_query.isra.0+0x280/0x280 [ib_core]
nldev_res_get_qp_dumpit+0x1e/0x30 [ib_core]
netlink_dump+0x16f/0x450 __netlink_dump_start+0x1ce/0x2e0 rdma_nl_rcv_msg+0x1d3/0x330 [ib_core]
? nldev_res_get_qp_raw_dumpit+0x30/0x30 [ib_core]
rdma_nl_rcv_skb.constprop.0.isra.0+0x108/0x180 [ib_core]
rdma_nl_rcv+0x12/0x20 [ib_core]
netlink_unicast+0x255/0x380 ? __alloc_skb+0xfa/0x1e0 netlink_sendmsg+0x1f3/0x420 __sock_sendmsg+0x38/0x60 ____sys_sendmsg+0x1e8/0x230 ? copy_msghdr_from_user+0xea/0x170 ___sys_sendmsg+0x7c/0xb0 ? __futex_wait+0x95/0xf0 ? __futex_wake_mark+0x40/0x40 ? futex_wait+0x67/0x100 ? futex_wake+0xac/0x1b0 __sys_sendmsg+0x5f/0xb0 do_syscall_64+0x55/0xb90 entry_SYSCALL_64_after_hwframe+0x4b/0x53
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Analysis
by VulDB Data Team • 09/18/2026
The Linux kernel contains a critical race condition vulnerability within the InfiniBand core subsystem, specifically affecting the Resource Tracker mechanism used to manage Queue Pair objects. This flaw arises from an improper synchronization sequence during the lifecycle management of Queue Pairs when accessed via the netlink interface. The issue stems from a timing gap between the initiation of resource deletion and the actual removal of the object from the tracking database. When a user space application initiates a query for Queue Pair attributes through the rdma_nl_rcv_msg path, it relies on rdma_restrack_get to acquire a reference count that ensures the underlying data structures remain valid during the read operation. However, when another thread or process triggers the destruction of the same Queue Pair via ib_destroy_qp_user, the system calls rdma_restrack_del only at the very end of the function. This delay creates a window where the vendor-specific resources associated with the Queue Pair are already freed and deallocated by hardware drivers such as mlx5_ib, yet the object remains visible in the resource tracker database because it has not been marked for deletion or removed from active tracking lists.
This architectural flaw leads to a classic use-after-free scenario that can be triggered remotely if an attacker possesses sufficient privileges to interact with the RDMA netlink interface. An adversary can exploit this race condition by simultaneously querying the state of a Queue Pair while another process is destroying it. Because the query operation checks for existence in the tracker before accessing memory, and the deletion logic does not immediately invalidate that entry until after vendor resources are released, the kernel may attempt to dereference pointers pointing to freed memory regions. The provided crash trace indicates a null pointer dereference or invalid memory access within ib_query_qp, which is invoked by fill_res_qp_entry_query during netlink dump operations. Such an exploit can result in system instability, denial of service through kernel panic, or potentially arbitrary code execution if the attacker can control the contents of the freed memory region and manipulate subsequent allocations to achieve a controlled overwrite.
From a security classification perspective, this vulnerability aligns with CWE-416, Use After Free, which describes situations where software continues to use a pointer after it has been freed, leading to undefined behavior. The attack vector involves local privilege escalation or denial of service depending on the context in which the race condition is triggered. In terms of adversarial tactics, this flaw relates to ATT&CK technique T1059, Command and Scripting Interpreter, specifically when used for reconnaissance via netlink sockets, although the primary impact here is system stability rather than direct command execution. The vulnerability highlights a common pitfall in kernel development where reference counting mechanisms are not tightly coupled with resource deallocation timelines, allowing stale references to persist beyond the validity of the underlying data structures they point to.
The resolution involves restructuring the destruction sequence within ib_destroy_qp_user by moving the rdma_restrack_begin_del call to the very beginning of the function rather than leaving it for the end. This change ensures that once the decision is made to destroy a Queue Pair, the object is immediately marked as being in a deletion state and removed from active tracking lists before any vendor-specific cleanup occurs. By doing so, subsequent queries or accesses via rdma_restrack_get will fail because the resource is no longer considered valid for access, thereby preventing the kernel from attempting to dereference freed memory. This synchronization fix effectively closes the race window by ensuring that the logical state of the object in the tracker database accurately reflects its physical availability and integrity.
To mitigate this vulnerability, system administrators should apply the latest available kernel patches that include this specific commit addressing the RDMA core use-after-free issue. For environments where immediate patching is not feasible, restricting access to netlink sockets used for RDMA resource management can reduce the attack surface. This involves configuring appropriate permissions on device nodes and ensuring that only trusted processes with root or specific capabilities can invoke rdma_nl_rcv_msg operations. Additionally, monitoring system logs for kernel panics or oops reports related to ib_core or mlx5_ib modules may help in detecting potential exploitation attempts before they cause significant service disruption. Regular auditing of RDMA configurations and limiting the scope of user access to high-performance computing resources are also recommended defensive measures to minimize exposure to such low-level concurrency bugs.