ceph: avoid 32-bit page index overflow

A pgoff_t is defined (by default) to have type (unsigned long).  On
architectures such as i686 that's a 32-bit type.  The ceph address
space code was attempting to produce 64 bit offsets by shifting a
page's index by PAGE_CACHE_SHIFT, but the result was not what was
desired because the shift occurred before the result got promoted
to 64 bits.

Fix this by converting all uses of page->index used in this way to
use the page_offset() macro, which ensures the 64-bit result has the
intended value.

This fixes http://tracker.newdream.net/issues/3112

Reported-by:  Mohamed Pakkeer <pakkeer.mohideen@realimage.com>
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

1 files changed, 5 insertions, 6 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 4469b63c9b7b..22b6e4583faa 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -205,7 +205,7 @@ static int readpage_nounlock(struct file *filp, struct page *page)
         dout("readpage inode %p file %p page %p index %lu\n",
              inode, filp, page, page->index);
         err = ceph_osdc_readpages(osdc, ceph_vino(inode), &ci->i_layout,
-                                  page->index << PAGE_CACHE_SHIFT, &len,
+                                  (u64) page_offset(page), &len,
                                   ci->i_truncate_seq, ci->i_truncate_size,
                                   &page, 1, 0);
         if (err == -ENOENT)
@@ -286,7 +286,7 @@ static int start_read(struct inode *inode, struct list_head *page_list, int max)
         int nr_pages = 0;
         int ret;
 
-        off = page->index << PAGE_CACHE_SHIFT;
+        off = (u64) page_offset(page);
 
         /* count pages */
         next_index = page->index;
@@ -426,7 +426,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
         struct ceph_inode_info *ci;
         struct ceph_fs_client *fsc;
         struct ceph_osd_client *osdc;
-        loff_t page_off = page->index << PAGE_CACHE_SHIFT;
+        loff_t page_off = page_offset(page);
         int len = PAGE_CACHE_SIZE;
         loff_t i_size;
         int err = 0;
@@ -817,8 +817,7 @@ get_more_pages:
                         /* ok */
                         if (locked_pages == 0) {
                                 /* prepare async write request */
-                                offset = (unsigned long long)page->index
-                                        << PAGE_CACHE_SHIFT;
+                                offset = (u64) page_offset(page);
                                 len = wsize;
                                 req = ceph_osdc_new_request(&fsc->client->osdc,
                                             &ci->i_layout,
@@ -1180,7 +1179,7 @@ static int ceph_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
         struct inode *inode = vma->vm_file->f_dentry->d_inode;
         struct page *page = vmf->page;
         struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
-        loff_t off = page->index << PAGE_CACHE_SHIFT;
+        loff_t off = page_offset(page);
         loff_t size, len;
         int ret;