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:
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.
git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f
git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de
git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6
git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69
git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c
git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330
git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43