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-rw-r--r--mm/mprotect.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 14f93e62270f..638edabaff71 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -123,6 +123,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
unsigned long oldflags = vma->vm_flags;
long nrpages = (end - start) >> PAGE_SHIFT;
unsigned long charged = 0;
+ unsigned int mask;
pgprot_t newprot;
pgoff_t pgoff;
int error;
@@ -149,8 +150,6 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
}
}
- newprot = protection_map[newflags & 0xf];
-
/*
* First try to merge with previous and/or next vma.
*/
@@ -177,6 +176,14 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
}
success:
+ /* Don't make the VMA automatically writable if it's shared, but the
+ * backer wishes to know when pages are first written to */
+ mask = VM_READ|VM_WRITE|VM_EXEC|VM_SHARED;
+ if (vma->vm_ops && vma->vm_ops->page_mkwrite)
+ mask &= ~VM_SHARED;
+
+ newprot = protection_map[newflags & mask];
+
/*
* vm_flags and vm_page_prot are protected by the mmap_sem
* held in write mode.