fix some conversion overflows

Fix page index to offset conversion overflows in buffer layer, ecryptfs,
and ocfs2.

It would be nice to convert the whole tree to page_offset, but for now
just fix the bugs.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 4 insertions, 5 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 02ebb1f1d3b0..0e5ec371ce72 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2221,7 +2221,7 @@ block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
         lock_page(page);
         size = i_size_read(inode);
         if ((page->mapping != inode->i_mapping) ||
-            ((page->index << PAGE_CACHE_SHIFT) > size)) {
+            (page_offset(page) > size)) {
                 /* page got truncated out from underneath us */
                 goto out_unlock;
         }
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 7d5a43cb0d5c..e4ab7bc14efe 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -409,8 +409,7 @@ static int ecryptfs_prepare_write(struct file *file, struct page *page,
         if (!PageUptodate(page))
                 rc = ecryptfs_do_readpage(file, page, page->index);
         if (page->index != 0) {
-                loff_t end_of_prev_pg_pos =
-                        (((loff_t)page->index << PAGE_CACHE_SHIFT) - 1);
+                loff_t end_of_prev_pg_pos = page_offset(page) - 1;
 
                 if (end_of_prev_pg_pos > i_size_read(page->mapping->host)) {
                         rc = ecryptfs_truncate(file->f_path.dentry,
@@ -736,7 +735,7 @@ static int ecryptfs_commit_write(struct file *file, struct page *page,
                 goto out;
         }
         inode->i_blocks = lower_inode->i_blocks;
-        pos = (page->index << PAGE_CACHE_SHIFT) + to;
+        pos = page_offset(page) + to;
         if (pos > i_size_read(inode)) {
                 i_size_write(inode, pos);
                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
diff --git a/fs/ocfs2/mmap.c b/fs/ocfs2/mmap.c
index ee64749e2eeb..98756156d298 100644
--- a/fs/ocfs2/mmap.c
+++ b/fs/ocfs2/mmap.c
@@ -89,7 +89,7 @@ static int __ocfs2_page_mkwrite(struct inode *inode, struct buffer_head *di_bh,
 {
         int ret;
         struct address_space *mapping = inode->i_mapping;
-        loff_t pos = page->index << PAGE_CACHE_SHIFT;
+        loff_t pos = page_offset(page);
         unsigned int len = PAGE_CACHE_SIZE;
         pgoff_t last_index;
         struct page *locked_page = NULL;