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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2017-03-09 16:17:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-03-09 17:01:10 -0800
commit8346242a7e32c4c93316684ad8f45473932586b9 (patch)
tree000c3008bcfb515913ceae12bb7d86cc0d032288
parentc9a1b80daeb50e39f21fd7e62f7224f317ac85f0 (diff)
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: c7ab0d2fdc84 ("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.com Signed-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>
-rw-r--r--mm/rmap.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 2da487d6cea8..250635dc47b7 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1316,12 +1316,6 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
}
while (page_vma_mapped_walk(&pvmw)) {
- subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
- address = pvmw.address;
-
- /* Unexpected PMD-mapped THP? */
- VM_BUG_ON_PAGE(!pvmw.pte, page);
-
/*
* If the page is mlock()d, we cannot swap it out.
* If it's recently referenced (perhaps page_referenced
@@ -1345,6 +1339,13 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
continue;
}
+ /* Unexpected PMD-mapped THP? */
+ VM_BUG_ON_PAGE(!pvmw.pte, page);
+
+ subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
+ address = pvmw.address;
+
+
if (!(flags & TTU_IGNORE_ACCESS)) {
if (ptep_clear_flush_young_notify(vma, address,
pvmw.pte)) {

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