| 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-2021-47461: userfaultfd: fix a race between writeprotect and exit_mmap() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| userfaultfd: fix a race between writeprotect and exit_mmap() |
| |
| A race is possible when a process exits, its VMAs are removed by |
| exit_mmap() and at the same time userfaultfd_writeprotect() is called. |
| |
| The race was detected by KASAN on a development kernel, but it appears |
| to be possible on vanilla kernels as well. |
| |
| Use mmget_not_zero() to prevent the race as done in other userfaultfd |
| operations. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47461 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.7 with commit 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 and fixed in 5.10.76 with commit 3cda4bfffd4f755645577aaa9e96a606657b4525 |
| Issue introduced in 5.7 with commit 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 and fixed in 5.14.15 with commit 149958ecd0627a9f1e9c678c25c665400054cd6a |
| Issue introduced in 5.7 with commit 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 and fixed in 5.15 with commit cb185d5f1ebf900f4ae3bf84cee212e6dd035aca |
| |
| 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-2021-47461 |
| 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: |
| fs/userfaultfd.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/3cda4bfffd4f755645577aaa9e96a606657b4525 |
| https://git.kernel.org/stable/c/149958ecd0627a9f1e9c678c25c665400054cd6a |
| https://git.kernel.org/stable/c/cb185d5f1ebf900f4ae3bf84cee212e6dd035aca |
