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.
OS | Version | Architecture | Package | Version | Filename |
---|---|---|---|---|---|
ubuntu | 18.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 20.04 | noarch | linux | < 5.4.0-80.90 | UNKNOWN |
ubuntu | 18.04 | noarch | linux-aws | < any | UNKNOWN |
ubuntu | 20.04 | noarch | linux-aws | < 5.4.0-1054.57 | UNKNOWN |
ubuntu | 18.04 | noarch | linux-aws-5.4 | < any | UNKNOWN |
ubuntu | 16.04 | noarch | linux-aws-hwe | < 4.15.0-1109.116~16.04.1 | UNKNOWN |
ubuntu | 20.04 | noarch | linux-azure | < 5.4.0-1055.57 | UNKNOWN |
ubuntu | 14.04 | noarch | linux-azure | < 4.15.0-1121.134~14.04.1 | UNKNOWN |
ubuntu | 16.04 | noarch | linux-azure | < 4.15.0-1121.134~16.04.1 | UNKNOWN |
ubuntu | 18.04 | noarch | linux-azure-4.15 | < any | UNKNOWN |
git.kernel.org/linus/7ed9d238c7dbb1fdb63ad96a6184985151b0171c (5.13-rc2)
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
launchpad.net/bugs/cve/CVE-2021-46988
nvd.nist.gov/vuln/detail/CVE-2021-46988
security-tracker.debian.org/tracker/CVE-2021-46988
www.cve.org/CVERecord?id=CVE-2021-46988