CVE-2021-46945 ext4: always panic when errors=panic is specified
A regression in the Linux kernel ext4 filesystem prevented panics when errors=panic was set, allowing potential denial of service under specific mount conditions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-46945?
CVE-2021-46945 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Feb 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:
ext4: always panic when errors=panic is specified
Before commit 014c9caa29d3 ("ext4: make ext4_abort() use __ext4_error()"), the following series of commands would trigger a panic:
1. mount /dev/sda -o ro,errors=panic test 2. mount /dev/sda -o remount,abort test
After commit 014c9caa29d3, remounting a file system using the test mount option "abort" will no longer trigger a panic. This commit will restore the behaviour immediately before commit 014c9caa29d3. (However, note that the Linux kernel's behavior has not been consistent; some previous kernel versions, including 5.4 and 4.19 similarly did not panic after using the mount option "abort".)
This also makes a change to long-standing behaviour; namely, the following series commands will now cause a panic, when previously it did not:
1. mount /dev/sda -o ro,errors=panic test 2. echo test > /sys/fs/ext4/sda/trigger_fs_error
However, this makes ext4's behaviour much more consistent, so this is a good thing.
Which versions are affected by CVE-2021-46945?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2021-46945?
No fix has been published for CVE-2021-46945 yet. Limit exposure of the affected software until one is available.
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-2021-46945 being exploited?
There is no known exploitation of CVE-2021-46945 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as GHSA-hx29-fw56-x5wj, UBUNTU-CVE-2021-46945.