CVE-2024-26627 scsi: core: Move scsi_host_busy() out of host lock for waking up EH handler
A Linux kernel SCSI bug causes hard lockups during error recovery when many requests are in-flight, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-26627?
CVE-2024-26627 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 Mar 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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 - 1) 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]
Which versions are affected by CVE-2024-26627?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-26627?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-26627 being exploited?
There is no known exploitation of CVE-2024-26627 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-26627, DEBIAN-CVE-2024-26627, GHSA-2cpc-3p3h-5rwq, UBUNTU-CVE-2024-26627.