CVE-2021-47556 ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce()
A local attacker can cause a kernel crash by triggering a NULL pointer dereference in ethtool coalesce settings on specific drivers.
- 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-2021-47556?
CVE-2021-47556 is a medium-severity vulnerability in Linux kernel, published on 24 May 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:
ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce()
ethtool_set_coalesce() now uses both the .get_coalesce() and .set_coalesce() callbacks. But the check for their availability is buggy, so changing the coalesce settings on a device where the driver provides only _one_ of the callbacks results in a NULL pointer dereference instead of an -EOPNOTSUPP.
Fix the condition so that the availability of both callbacks is ensured. This also matches the netlink code.
Note that reproducing this requires some effort - it only affects the legacy ioctl path, and needs a specific combination of driver options: - have .get_coalesce() and .coalesce_supported but no .set_coalesce(), or - have .set_coalesce() but no .get_coalesce(). Here eg. ethtool doesn't cause the crash as it first attempts to call ethtool_get_coalesce() and bails out on error.
Weakness: CWE-476
Which versions are affected by CVE-2021-47556?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2021-47556?
Apply the vendor's patch.
Is CVE-2021-47556 being exploited?
There is no known exploitation of CVE-2021-47556 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2021-47556, UBUNTU-CVE-2021-47556.