Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
scsi: core: Wake up the error handler when final completions race against each other
The fragile ordering between marking commands completed or failed so that the error handler only wakes when the last running command completes or times out has race conditions. These race conditions can cause the SCSI layer to fail to wake the error handler, leaving I/O through the SCSI host stuck as the error state cannot advance.
First, there is an memory ordering issue within scsi_dec_host_busy(). The write which clears SCMD_STATE_INFLIGHT may be reordered with reads counting in scsi_host_busy(). While the local CPU will see its own write, reordering can allow other CPUs in scsi_dec_host_busy() or scsi_eh_inc_host_failed() to see a raised busy count, causing no CPU to see a host busy equal to the host_failed count.
This race condition can be prevented with a memory barrier on the error path to force the write to be visible before counting host busy commands.
Second, there is a general ordering issue with scsi_eh_inc_host_failed(). By counting busy commands before incrementing host_failed, it can race with a final command in scsi_dec_host_busy(), such that scsi_dec_host_busy() does not see host_failed incremented but scsi_eh_inc_host_failed() counts busy commands before SCMD_STATE_INFLIGHT is cleared by scsi_dec_host_busy(), resulting in neither waking the error handler task.
This needs the call to scsi_host_busy() to be moved after host_failed is incremented to close the race condition.
Details
- Affected product:
- AlmaLinux 9.2 ESU , Amazon Linux 2 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , TuxCare 9.6 ESU
- Affected packages:
- kernel @ 5.14.0 (+5 more)
Fixes
KernelCare state
Live-patch status from KernelCare for each operating system.
| Operating system | Status | Covered kernels |
|---|---|---|
| AlmaLinux 9.6 ESU | Released |
11 kernels
|
| Amazon Linux 2023 | Ready For Release | — |
| Debian 11 | Released |
37 kernels
|
| Debian 11 cloud | Released |
17 kernels
|
| Debian 12 | Planned | — |
| Debian 13 | Planned | — |
| RHEL 10 | Planned | — |
| RHEL 9 | In Progress | — |
| Ubuntu 24.04 | Released |
43 kernels
|
| Ubuntu 24.04 AWS | Planned | — |