Bug 2481932 (CVE-2026-45973)

Summary: CVE-2026-45973 kernel: RDMA/mlx5: Fix UMR hang in LAG error state unload
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's RDMA/mlx5 driver. A race condition during firmware reset in Link Aggregation Group (LAG) mode can cause the driver to hang indefinitely while waiting for Unregister Memory Region (UMR) completion during device unload. This can lead to a denial of service, making the affected system unresponsive.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-05-27 15:02:59 UTC 
In the Linux kernel, the following vulnerability has been resolved:

RDMA/mlx5: Fix UMR hang in LAG error state unload

During firmware reset in LAG mode, a race condition causes the driver
to hang indefinitely while waiting for UMR completion during device
unload. See [1].

In LAG mode the bond device is only registered on the master, so it
never sees sys_error events from the slave.
During firmware reset this causes UMR waits to hang forever on unload
as the slave is dead but the master hasn't entered error state yet, so
UMR posts succeed but completions never arrive.

Fix this by adding a sys_error notifier that gets registered before
MLX5_IB_STAGE_IB_REG and stays alive until after ib_unregister_device().
This ensures error events reach the bond device throughout teardown.

[1]
Call Trace:
 __schedule+0x2bd/0x760
 schedule+0x37/0xa0
 schedule_preempt_disabled+0xa/0x10
 __mutex_lock.isra.6+0x2b5/0x4a0
 __mlx5_ib_dereg_mr+0x606/0x870 [mlx5_ib]
 ? __xa_erase+0x4a/0xa0
 ? _cond_resched+0x15/0x30
 ? wait_for_completion+0x31/0x100
 ib_dereg_mr_user+0x48/0xc0 [ib_core]
 ? rdmacg_uncharge_hierarchy+0xa0/0x100
 destroy_hw_idr_uobject+0x20/0x50 [ib_uverbs]
 uverbs_destroy_uobject+0x37/0x150 [ib_uverbs]
 __uverbs_cleanup_ufile+0xda/0x140 [ib_uverbs]
 uverbs_destroy_ufile_hw+0x3a/0xf0 [ib_uverbs]
 ib_uverbs_remove_one+0xc3/0x140 [ib_uverbs]
 remove_client_context+0x8b/0xd0 [ib_core]
 disable_device+0x8c/0x130 [ib_core]
 __ib_unregister_device+0x10d/0x180 [ib_core]
 ib_unregister_device+0x21/0x30 [ib_core]
 __mlx5_ib_remove+0x1e4/0x1f0 [mlx5_ib]
 auxiliary_bus_remove+0x1e/0x30
 device_release_driver_internal+0x103/0x1f0
 bus_remove_device+0xf7/0x170
 device_del+0x181/0x410
 mlx5_rescan_drivers_locked.part.10+0xa9/0x1d0 [mlx5_core]
 mlx5_disable_lag+0x253/0x260 [mlx5_core]
 mlx5_lag_disable_change+0x89/0xc0 [mlx5_core]
 mlx5_eswitch_disable+0x67/0xa0 [mlx5_core]
 mlx5_unload+0x15/0xd0 [mlx5_core]
 mlx5_unload_one+0x71/0xc0 [mlx5_core]
 mlx5_sync_reset_reload_work+0x83/0x100 [mlx5_core]
 process_one_work+0x1a7/0x360
 worker_thread+0x30/0x390
 ? create_worker+0x1a0/0x1a0
 kthread+0x116/0x130
 ? kthread_flush_work_fn+0x10/0x10
 ret_from_fork+0x22/0x40
Comment 1 Keith Grant 2026-05-27 22:38:56 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026052736-CVE-2026-45973-7864@gregkh/T