[PATCH] Remove SUID when splicing into an inode

Originally from Mark Fasheh <mark.fasheh@oracle.com>

generic_file_splice_write() does not remove S_ISUID or S_ISGID. This is
inconsistent with the way we generally write to files.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/splice.c

@@ -845,6 +845,10 @@ generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 	ssize_t ret;
 	int err;
 
+	err = remove_suid(out->f_dentry);
+	if (unlikely(err))
+		return err;
+
 	ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 	if (ret > 0) {
 		*ppos += ret;
@@ -883,21 +887,28 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 			  loff_t *ppos, size_t len, unsigned int flags)
 {
 	struct address_space *mapping = out->f_mapping;
+	struct inode *inode = mapping->host;
 	ssize_t ret;
+	int err;
+
+	err = should_remove_suid(out->f_dentry);
+	if (unlikely(err)) {
+		mutex_lock(&inode->i_mutex);
+		err = __remove_suid(out->f_dentry, err);
+		mutex_unlock(&inode->i_mutex);
+		if (err)
+			return err;
+	}
 
 	ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 	if (ret > 0) {
-		struct inode *inode = mapping->host;
-
 		*ppos += ret;
 
 		/*
 		 * If file or inode is SYNC and we actually wrote some data,
 		 * sync it.
 		 */
 		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
-			int err;
-
 			mutex_lock(&inode->i_mutex);
 			err = generic_osync_inode(inode, mapping,
 						  OSYNC_METADATA|OSYNC_DATA);