CVE-2021-46904 net: hso: fix null-ptr-deref during tty device unregistration
A null pointer dereference in the Linux kernel hso driver during tty unregistration can cause a system crash.
- 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-2021-46904?
CVE-2021-46904 is a medium-severity vulnerability in Linux kernel, published on 25 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:
net: hso: fix null-ptr-deref during tty device unregistration
Multiple ttys try to claim the same the minor number causing a double unregistration of the same device. The first unregistration succeeds but the next one results in a null-ptr-deref.
The get_free_serial_index() function returns an available minor number but doesn't assign it immediately. The assignment is done by the caller later. But before this assignment, calls to get_free_serial_index() would return the same minor number.
Fix this by modifying get_free_serial_index to assign the minor number immediately after one is found to be and rename it to obtain_minor() to better reflect what it does. Similary, rename set_serial_by_index() to release_minor() and modify it to free up the minor number of the given hso_serial. Every obtain_minor() should have corresponding release_minor() call.
Weakness: CWE-476
Which versions are affected by CVE-2021-46904?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2021-46904?
Apply the vendor's patch.
Is CVE-2021-46904 being exploited?
There is no known exploitation of CVE-2021-46904 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2021-46904, GHSA-r633-2867-crc8, UBUNTU-CVE-2021-46904.