CVE-2022-48862 vhost: fix hung thread due to erroneous iotlb entries
A local attacker can cause a kernel thread hang and denial of service by sending a specific IOTLB message with zero size to the vhost driver.
- 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-2022-48862?
CVE-2022-48862 is a medium-severity denial of service vulnerability in Linux kernel, published on 16 Jul 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:
vhost: fix hung thread due to erroneous iotlb entries
In vhost_iotlb_add_range_ctx(), range size can overflow to 0 when start is 0 and last is ULONG_MAX. One instance where it can happen is when userspace sends an IOTLB message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an entry with size = 0, start = 0, last = ULONG_MAX ends up in the iotlb. Next time a packet is sent, iotlb_access_ok() loops indefinitely due to that erroneous entry.
Call Trace: <TASK> iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340 vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366 vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104 vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372 kthread+0x2e9/0x3a0 kernel/kthread.c:377 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK>
Reported by syzbot at: https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
To fix this, do two things:
1. Return -EINVAL in vhost_chr_write_iter() when userspace asks to map a range with size 0. 2. Fix vhost_iotlb_add_range_ctx() to handle the range [0, ULONG_MAX] by splitting it into two entries.
Weakness: CWE-835
Which versions are affected by CVE-2022-48862?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-48862?
Apply the vendor's patch.
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-2022-48862 being exploited?
There is no known exploitation of CVE-2022-48862 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-48862, GHSA-cqc3-8mfm-84p4, ROOT-OS-DEBIAN-11-CVE-2022-48862, UBUNTU-CVE-2022-48862.