fs: update atime before I/O in generic_file_read_iter

After the call to ->direct_IO the final reference to the file might have
been dropped by aio_complete already, and the call to file_accessed might
cause a use after free.

Instead update the access time before the I/O, similar to how we
update the time stamps before writes.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/mm/filemap.c b/mm/filemap.c
index 8a287df..2f1175e 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1910,16 +1910,18 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
        if (iocb->ki_flags & IOCB_DIRECT) {
                struct address_space *mapping = file->f_mapping;
                struct inode *inode = mapping->host;
+               struct iov_iter data = *iter;
                loff_t size;
 
                size = i_size_read(inode);
                retval = filemap_write_and_wait_range(mapping, iocb->ki_pos,
                                        iocb->ki_pos + count - 1);
-               if (!retval) {
-                       struct iov_iter data = *iter;
-                       retval = mapping->a_ops->direct_IO(iocb, &data);
-               }
+               if (retval < 0)
+                       goto out;
 
+               file_accessed(file);
+
+               retval = mapping->a_ops->direct_IO(iocb, &data);
                if (retval > 0) {
                        iocb->ki_pos += retval;
                        iov_iter_advance(iter, retval);
@@ -1935,10 +1937,8 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
                 * DAX files, so don't bother trying.
                 */
                if (retval < 0 || !iov_iter_count(iter) || iocb->ki_pos >= size ||
-                   IS_DAX(inode)) {
-                       file_accessed(file);
+                   IS_DAX(inode))
                        goto out;
-               }
        }
 
        retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);