CVE-2024-26885 bpf: Fix DEVMAP_HASH overflow check on 32-bit arches
An integer overflow in the Linux kernel BPF devmap code allows local attackers to cause a system crash on 32-bit architectures.
- 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-2024-26885?
CVE-2024-26885 is a high-severity vulnerability in Linux kernel, published on 17 Apr 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:
bpf: Fix DEVMAP_HASH overflow check on 32-bit arches
The devmap code allocates a number hash buckets equal to the next power of two of the max_entries value provided when creating the map. When rounding up to the next power of two, the 32-bit variable storing the number of buckets can overflow, and the code checks for overflow by checking if the truncated 32-bit value is equal to 0. However, on 32-bit arches the rounding up itself can overflow mid-way through, because it ends up doing a left-shift of 32 bits on an unsigned long value. If the size of an unsigned long is four bytes, this is undefined behaviour, so there is no guarantee that we'll end up with a nice and tidy 0-value at the end.
Syzbot managed to turn this into a crash on arm32 by creating a DEVMAP_HASH with max_entries > 0x80000000 and then trying to update it. Fix this by moving the overflow check to before the rounding up operation.
Weakness: CWE-119
Which versions are affected by CVE-2024-26885?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-26885?
Apply the vendor's patch.
Is CVE-2024-26885 being exploited?
There is no known exploitation of CVE-2024-26885 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-40091, BELL-CVE-2024-26885, DEBIAN-CVE-2024-26885, GHSA-5rcv-qpv8-9248, UBUNTU-CVE-2024-26885.