CVE-2024-26627

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]

More information : https://git.kernel.org/stable/c/07e3ca0f17f579491b5f54e9ed05173d6c1d6fcb