# CVE-2021-47214: linux: In the Linux kernel, the following vulnerability has been resolved:  hugetlb, userfaultfd: fix reservation restore on...

CVE-2021-47214 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47214, released April 10, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-47214
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0019
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 10, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  hugetlb, userfaultfd: fix reservation restore on userfaultfd error  Currently in the is_continue case in hugetlb_mcopy_atomic_pte(), if we bail out using "goto out_release_unlock;" in the cases where idx >= size, or !huge_pte_none(), the code will detect that new_pagecache_page == false, and so call restore_reserve_on_error().  In this case I see restore_reserve_on_error() delete the reservation, and the following call to remove_inode_hugepages() will increment h->resv_hugepages causing a 100% reproducible leak.  We should treat the is_continue case similar to adding a page into the pagecache and set new_pagecache_page to true, to indicate that there is no reservation to restore on the error path, and we need not call restore_reserve_on_error().  Rename new_pagecache_page to page_in_pagecache to make that clear.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.15.5-1 | [DEBIAN-CVE-2021-47214](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47214.md) | Apr 10, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.15.5-1 | [DEBIAN-CVE-2021-47214](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47214.md) | Apr 10, 2024 |
| Linux | linux Debian 14 | 5.15.5-1 | [DEBIAN-CVE-2021-47214](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47214.md) | Apr 10, 2024 |

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