1 files changed, 46 insertions, 4 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index ed884dd9674b..454bd35c8ab0 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -6,6 +6,7 @@
  * Address space accounting code	<alan@lxorguk.ukuu.org.uk>
  */
 
+#include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/backing-dev.h>
 #include <linux/mm.h>
@@ -392,6 +393,34 @@ find_vma_prepare(struct mm_struct *mm, unsigned long addr,
 	return vma;
 }
 
+static unsigned long count_vma_pages_range(struct mm_struct *mm,
+		unsigned long addr, unsigned long end)
+{
+	unsigned long nr_pages = 0;
+	struct vm_area_struct *vma;
+
+	/* Find first overlaping mapping */
+	vma = find_vma_intersection(mm, addr, end);
+	if (!vma)
+		return 0;
+
+	nr_pages = (min(end, vma->vm_end) -
+		max(addr, vma->vm_start)) >> PAGE_SHIFT;
+
+	/* Iterate over the rest of the overlaps */
+	for (vma = vma->vm_next; vma; vma = vma->vm_next) {
+		unsigned long overlap_len;
+
+		if (vma->vm_start > end)
+			break;
+
+		overlap_len = min(end, vma->vm_end) - vma->vm_start;
+		nr_pages += overlap_len >> PAGE_SHIFT;
+	}
+
+	return nr_pages;
+}
+
 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
 		struct rb_node **rb_link, struct rb_node *rb_parent)
 {
@@ -1245,6 +1274,23 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	unsigned long charged = 0;
 	struct inode *inode =  file ? file->f_path.dentry->d_inode : NULL;
 
+	/* Check against address space limit. */
+	if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
+		unsigned long nr_pages;
+
+		/*
+		 * MAP_FIXED may remove pages of mappings that intersects with
+		 * requested mapping. Account for the pages it would unmap.
+		 */
+		if (!(vm_flags & MAP_FIXED))
+			return -ENOMEM;
+
+		nr_pages = count_vma_pages_range(mm, addr, addr + len);
+
+		if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))
+			return -ENOMEM;
+	}
+
 	/* Clear old maps */
 	error = -ENOMEM;
 munmap_back:
@@ -1255,10 +1301,6 @@ munmap_back:
 		goto munmap_back;
 	}
 
-	/* Check against address space limit. */
-	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
-		return -ENOMEM;
-
 	/*
 	 * Set 'VM_NORESERVE' if we should not account for the
 	 * memory use of this mapping.