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authorLinus Torvalds <torvalds@linux-foundation.org>2010-08-20 16:39:25 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-26 16:41:44 -0700
commitb3ef5ce3d1bc48506a1ac5b046de0ccda7b02d07 (patch)
treed0ab396aaad08b4d0cd564e423631efe635750f6 /mm
parent378776c287c66b32ff9a62c34a9715f702dc336e (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>
Diffstat (limited to 'mm')
-rw-r--r--mm/mlock.c21
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) {