Ubuntu: (CVE-2021-46988): linux vulnerability
Description
In the Linux kernel, the following vulnerability has been resolved: userfaultfd: release page in error path to avoid BUG_ON Consider the following sequence of events: 1. Userspace issues a UFFD ioctl, which ends up calling into shmem_mfill_atomic_pte(). We successfully account the blocks, we shmem_alloc_page(), but then the copy_from_user() fails. We return -ENOENT. We don't release the page we allocated. 2. Our caller detects this error code, tries the copy_from_user() after dropping the mmap_lock, and retries, calling back into shmem_mfill_atomic_pte(). 3. Meanwhile, let's say another process filled up the tmpfs being used. 4. So shmem_mfill_atomic_pte() fails to account blocks this time, and immediately returns - without releasing the page. This triggers a BUG_ON in our caller, which asserts that the page should always be consumed, unless -ENOENT is returned. To fix this, detect if we have such a "dangling" page when accounting fails, and if so, release it before returning.
Solution(s)
- ubuntu-upgrade-linux
- ubuntu-upgrade-linux-aws
- ubuntu-upgrade-linux-aws-5-4
- ubuntu-upgrade-linux-aws-hwe
- ubuntu-upgrade-linux-azure
- ubuntu-upgrade-linux-azure-4-15
- ubuntu-upgrade-linux-azure-5-4
- ubuntu-upgrade-linux-bluefield
- ubuntu-upgrade-linux-gcp
- ubuntu-upgrade-linux-gcp-4-15
- ubuntu-upgrade-linux-gcp-5-4
- ubuntu-upgrade-linux-gkeop
- ubuntu-upgrade-linux-hwe
- ubuntu-upgrade-linux-hwe-5-4
- ubuntu-upgrade-linux-kvm
- ubuntu-upgrade-linux-oracle
- ubuntu-upgrade-linux-oracle-5-4
- ubuntu-upgrade-linux-raspi
- ubuntu-upgrade-linux-raspi-5-4
- Lightweight Endpoint Agent
- Live Dashboards
- Real Risk Prioritization
- IT-Integrated Remediation Projects
- Cloud, Virtual, and Container Assessment
- Integrated Threat Feeds
- Easy-to-Use RESTful API
- Automation-Assisted Patching
- Automated Containment
With Rapid7 live dashboards, I have a clear view of all the assets on my network, which ones can be exploited, and what I need to do in order to reduce the risk in my environment in real-time. No other tool gives us that kind of value and insight.
– Scott Cheney, Manager of Information Security, Sierra View Medical Center