CVE-2025-68790
Description
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: Fix double unregister of HCA_PORTS component
Clear hca_devcom_comp in device's private data after unregistering it in LAG teardown. Otherwise a slightly lagging second pass through mlx5_unload_one() might try to unregister it again and trip over use-after-free.
On s390 almost all PCI level recovery events trigger two passes through mxl5_unload_one() - one through the poll_health() method and one through mlx5_pci_err_detected() as callback from generic PCI error recovery. While testing PCI error recovery paths with more kernel debug features enabled, this issue reproducibly led to kernel panics with the following call chain:
Unable to handle kernel pointer dereference in virtual kernel address space Failing address: 6b6b6b6b6b6b6000 TEID: 6b6b6b6b6b6b6803 ESOP-2 FSI Fault in home space mode while using kernel ASCE. AS:00000000705c4007 R3:0000000000000024 Oops: 0038 ilc:3 [#1]SMP
CPU: 14 UID: 0 PID: 156 Comm: kmcheck Kdump: loaded Not tainted 6.18.0-20251130.rc7.git0.16131a59cab1.300.fc43.s390x+debug #1 PREEMPT
Krnl PSW : 0404e00180000000 0000020fc86aa1dc (__lock_acquire+0x5c/0x15f0) R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000000 0000020f00000001 6b6b6b6b6b6b6c33 0000000000000000 0000000000000000 0000000000000000 0000000000000001 0000000000000000 0000000000000000 0000020fca28b820 0000000000000000 0000010a1ced8100 0000010a1ced8100 0000020fc9775068 0000018fce14f8b8 0000018fce14f7f8 Krnl Code: 0000020fc86aa1cc: e3b003400004 lg %r11,832 0000020fc86aa1d2: a7840211 brc 8,0000020fc86aa5f4 *0000020fc86aa1d6: c09000df0b25 larl %r9,0000020fca28b820 >0000020fc86aa1dc: d50790002000 clc 0(8,%r9),0(%r2) 0000020fc86aa1e2: a7840209 brc 8,0000020fc86aa5f4 0000020fc86aa1e6: c0e001100401 larl %r14,0000020fca8aa9e8 0000020fc86aa1ec: c01000e25a00 larl %r1,0000020fca2f55ec 0000020fc86aa1f2: a7eb00e8 aghi %r14,232
Call Trace: __lock_acquire+0x5c/0x15f0 lock_acquire.part.0+0xf8/0x270 lock_acquire+0xb0/0x1b0 down_write+0x5a/0x250 mlx5_detach_device+0x42/0x110 [mlx5_core] mlx5_unload_one_devl_locked+0x50/0xc0 [mlx5_core] mlx5_unload_one+0x42/0x60 [mlx5_core] mlx5_pci_err_detected+0x94/0x150 [mlx5_core] zpci_event_attempt_error_recovery+0xcc/0x388
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A double-unregister use-after-free in mlx5 HCA_PORTS component can cause kernel panics on s390 during PCI error recovery.
Root
Cause
In the Linux kernel's mlx5 driver, the HCA_PORTS component's device completion structure (hca_devcom_comp) is not cleared from the device private data after it is unregistered during LAG teardown. This omission allows a subsequent call to mlx5_unload_one() to attempt a second unregister on an already freed structure, triggering a use-after-free [1].
Trigger and
Exploitation
The flaw is easily reached on s390 systems where almost all PCI level recovery events produce two paths into mlx5_unload_one(): one via the poll_health() method and another via mlx5_pci_err_detected() as a callback from generic PCI error recovery. No special attacker interaction is required; the race occurs during normal kernel error handling. An attacker would need no authentication or network access—the bug is a reliability issue that manifests during standard recovery procedures [1].
Impact
When the double unregister occurs, the kernel dereferences freed memory (as seen in the call trace pointing to __lock_acquire operating on a 6b6b6b6b6b6b6000 address pattern typical of use-after-free). This leads to a system panic (Oops), causing denial of service. There is no indication of privilege escalation or data confidentiality loss; the primary consequence is system instability and downtime [1].
Mitigation
The fix [1] clears hca_devcom_comp after unregistering it in LAG teardown, preventing the second pass from attempting a stale unregister. The patch has been committed to the Linux kernel stable tree. Users are advised to apply the latest stable kernel updates containing this commit. No workaround aside from patching is available.
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
1Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
2News mentions
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