CVE-2021-46988

Summary

CVE-2021-46988 is a vulnerability in the Linux kernel that affects the userfaultfd (UFFD) subsystem. In certain scenarios, a user space process may fail to allocate memory using UFFD, causing an allocated page to be left "dangling" without being released. If another process attempts to use the same temporary filesystem (tmpfs) location, the tmpfs may become filled, preventing the UFFD subsystem from accounting for the blocks required for the dangling page. In turn, this can trigger a BUG_ON assertion in the kernel, leading to system instability or potential security vulnerabilities. The issue has been resolved by detecting and releasing the dangling page when memory accounting fails.

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