CVE ID:	CVE-2021-47461
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.
Test IDs:	None available
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2021-47461 https://git.kernel.org/stable/c/149958ecd0627a9f1e9c678c25c665400054cd6a https://git.kernel.org/stable/c/149958ecd0627a9f1e9c678c25c665400054cd6a https://git.kernel.org/stable/c/3cda4bfffd4f755645577aaa9e96a606657b4525 https://git.kernel.org/stable/c/3cda4bfffd4f755645577aaa9e96a606657b4525 https://git.kernel.org/stable/c/cb185d5f1ebf900f4ae3bf84cee212e6dd035aca https://git.kernel.org/stable/c/cb185d5f1ebf900f4ae3bf84cee212e6dd035aca