diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2010-08-20 16:39:25 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-08-26 16:41:44 -0700 |
| commit | b3ef5ce3d1bc48506a1ac5b046de0ccda7b02d07 (patch) | |
| tree | d0ab396aaad08b4d0cd564e423631efe635750f6 | |
| parent | 378776c287c66b32ff9a62c34a9715f702dc336e (diff) | |
mm: make the mlock() stack guard page checks stricter
commit 7798330ac8114c731cfab83e634c6ecedaa233d7 upstream.
If we've split the stack vma, only the lowest one has the guard page.
Now that we have a doubly linked list of vma's, checking this is trivial.
Tested-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | mm/mlock.c | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/mm/mlock.c b/mm/mlock.c index 524d2a444ef7..380ea896c17b 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -138,6 +138,19 @@ void munlock_vma_page(struct page *page) } } +/* Is the vma a continuation of the stack vma above it? */ +static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr) +{ + return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN); +} + +static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr) +{ + return (vma->vm_flags & VM_GROWSDOWN) && + (vma->vm_start == addr) && + !vma_stack_continue(vma->vm_prev, addr); +} + /** * __mlock_vma_pages_range() - mlock a range of pages in the vma. * @vma: target vma @@ -171,11 +184,9 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma, gup_flags |= FOLL_WRITE; /* We don't try to access the guard page of a stack vma */ - if (vma->vm_flags & VM_GROWSDOWN) { - if (start == vma->vm_start) { - start += PAGE_SIZE; - nr_pages--; - } + if (stack_guard_page(vma, start)) { + addr += PAGE_SIZE; + nr_pages--; } while (nr_pages > 0) { |