rmap: fix NULL-pointer dereference on THP munlocking
The following test case triggers NULL-pointer derefernce in try_to_unmap_one(): #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <sys/mman.h> int main(int argc, char *argv[]) { int fd; system("mount -t tmpfs -o huge=always none /mnt"); fd = open("/mnt/test", O_CREAT | O_RDWR); ftruncate(fd, 2UL << 20); mmap(NULL, 2UL << 20, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED | MAP_LOCKED, fd, 0); mmap(NULL, 2UL << 20, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_LOCKED, fd, 0); munlockall(); return 0; } Apparently, there's a case when we call try_to_unmap() on huge PMDs: it's TTU_MUNLOCK. Let's handle this case correctly. Fixes: c7ab0d2f ("mm: convert try_to_unmap_one() to use page_vma_mapped_walk()") Link: http://lkml.kernel.org/r/20170302151159.30592-1-kirill.shutemov@linux.intel.comSigned-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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