| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47214: hugetlb, userfaultfd: fix reservation restore on userfaultfd error |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47214 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.14 with commit c7b1850dfb41d0b4154aca8dbc04777fbd75616f and fixed in 5.15.5 with commit b5069d44e2fbc4a9093d005b3ef0949add3dd27e |
| Issue introduced in 5.14 with commit c7b1850dfb41d0b4154aca8dbc04777fbd75616f and fixed in 5.16 with commit cc30042df6fcc82ea18acf0dace831503e60a0b7 |
| Issue introduced in 5.13.13 with commit 515b6124df6a84c957c5cc6bb6e8309dae7b1e9c |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47214 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| mm/hugetlb.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/b5069d44e2fbc4a9093d005b3ef0949add3dd27e |
| https://git.kernel.org/stable/c/cc30042df6fcc82ea18acf0dace831503e60a0b7 |
