In the Linux kernel, the following vulnerability has been resolved: userfaultfd: fix a race between writeprotect and exitmmap() A race is possible when a process exits, its VMAs are removed by exitmmap() and at the same time userfaultfdwriteprotect() is called. The race was detected by KASAN on a development kernel, but it appears to be possible on vanilla kernels as well. Use mmgetnot_zero() to prevent the race as done in other userfaultfd operations.