CVE-2021-47192 scsi: core: sysfs: Fix hang when device state is set via sysfs
A race condition in the Linux kernel SCSI subsystem can cause a system hang when setting device state via sysfs during iSCSI recovery.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-47192?
CVE-2021-47192 is a medium-severity vulnerability in Linux kernel, published on 10 Apr 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
scsi: core: sysfs: Fix hang when device state is set via sysfs
This fixes a regression added with:
commit f0f82e2476f6 ("scsi: core: Fix capacity set to zero after offlinining device")
The problem is that after iSCSI recovery, iscsid will call into the kernel to set the dev's state to running, and with that patch we now call scsi_rescan_device() with the state_mutex held. If the SCSI error handler thread is just starting to test the device in scsi_send_eh_cmnd() then it's going to try to grab the state_mutex.
We are then stuck, because when scsi_rescan_device() tries to send its I/O scsi_queue_rq() calls -> scsi_host_queue_ready() -> scsi_host_in_recovery() which will return true (the host state is still in recovery) and I/O will just be requeued. scsi_send_eh_cmnd() will then never be able to grab the state_mutex to finish error handling.
To prevent the deadlock move the rescan-related code to after we drop the state_mutex.
This also adds a check for if we are already in the running state. This prevents extra scans and helps the iscsid case where if the transport class has already onlined the device during its recovery process then we don't need userspace to do it again plus possibly block that daemon.
Weakness: CWE-667
Which versions are affected by CVE-2021-47192?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2021-47192?
Apply the vendor's patch.
Is CVE-2021-47192 being exploited?
There is no known exploitation of CVE-2021-47192 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2021-47192, GHSA-f834-hvgh-g5v9, UBUNTU-CVE-2021-47192.