diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2017-03-09 16:17:20 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-03-09 17:01:10 -0800 |
| commit | 8346242a7e32c4c93316684ad8f45473932586b9 (patch) | |
| tree | 000c3008bcfb515913ceae12bb7d86cc0d032288 /mm | |
| parent | c9a1b80daeb50e39f21fd7e62f7224f317ac85f0 (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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/rmap.c | 13 |
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)) { |