Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
scsi: core: Move scsi_host_busy() out of host lock for waking up EH handler
Inside scsi_eh_wakeup(), scsi_host_busy() is called & checked with host lock every time for deciding if error handler kthread needs to be waken up.
This can be too heavy in case of recovery, such as:
-
N hardware queues
-
queue depth is M for each hardware queue
-
each scsi_host_busy() iterates over (N * M) tag/requests
If recovery is triggered in case that all requests are in-flight, each scsi_eh_wakeup() is strictly serialized, when scsi_eh_wakeup() is called for the last in-flight request, scsi_host_busy() has been run for (N * M -
- times, and request has been iterated for (N*M - 1) * (N * M) times.
If both N and M are big enough, hard lockup can be triggered on acquiring host lock, and it is observed on mpi3mr(128 hw queues, queue depth 8169).
Fix the issue by calling scsi_host_busy() outside the host lock. We don’t need the host lock for getting busy count because host the lock never covers that.
[mkp: Drop unnecessary ‘busy’ variables pointed out by Bart]
Details
- Affected product:
- AlmaLinux 9.2 ESU , Amazon Linux 2 ELS , Debian 10 ELS , TuxCare 9.6 ESU
- Affected packages:
- kernel @ 5.14.0 (+3 more)
Fixes
KernelCare state
Live-patch status from KernelCare for each operating system.
| Operating system | Status | Covered kernels |
|---|---|---|
| Amazon Linux 2 5.10 | Will Not Fix | — |
| Debian 11 | Released |
28 kernels
|
| Debian 11 cloud | Released |
8 kernels
|
| Debian 12 | Planned | — |
| Proxmox VE 7 5.15 | Released |
43 kernels
|
| Ubuntu 20.04 HWE AWS | Released |
37 kernels
|
| Ubuntu 20.04 HWE Azure | Released |
21 kernels
|
| Ubuntu 22.04 | Released |
50 kernels
|
| Ubuntu 22.04 AWS | Released |
44 kernels
|
| Ubuntu 22.04 Azure | Released |
41 kernels
|