CVE - CVE-2021-46988

CVE-ID
CVE-2021-46988	Learn more at National Vulnerability Database (NVD) • CVSS Severity Rating • Fix Information • Vulnerable Software Versions • SCAP Mappings • CPE Information
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.
References
Note: References are provided for the convenience of the reader to help distinguish between vulnerabilities. The list is not intended to be complete.
MISC:https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f URL:https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f MISC:https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de URL:https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de MISC:https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6 URL:https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6 MISC:https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69 URL:https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69 MISC:https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c URL:https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c MISC:https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330 URL:https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330 MISC:https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43 URL:https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43
Assigning CNA
kernel.org
Date Record Created
20240227	Disclaimer: The record creation date may reflect when the CVE ID was allocated or reserved, and does not necessarily indicate when this vulnerability was discovered, shared with the affected vendor, publicly disclosed, or updated in CVE.
Phase (Legacy)
Assigned (20240227)
Votes (Legacy)

Comments (Legacy)

Proposed (Legacy)
N/A
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