vfs: splice remove_suid() cleanup

generic_file_splice_write() duplicates remove_suid() just because it
doesn't hold i_mutex.  But it grabs i_mutex inside splice_from_pipe()
anyway, so this is rather pointless.

Move locking to generic_file_splice_write() and call remove_suid() and
__splice_from_pipe() instead.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

3 files changed, 14 insertions, 18 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 633f58ebfb72..cece15b4ef72 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -811,24 +811,19 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 {
 	struct address_space *mapping = out->f_mapping;
 	struct inode *inode = mapping->host;
-	int killsuid, killpriv;
+	struct splice_desc sd = {
+		.total_len = len,
+		.flags = flags,
+		.pos = *ppos,
+		.u.file = out,
+	};
 	ssize_t ret;
-	int err = 0;
-
-	killpriv = security_inode_need_killpriv(out->f_path.dentry);
-	killsuid = should_remove_suid(out->f_path.dentry);
-	if (unlikely(killsuid || killpriv)) {
-		mutex_lock(&inode->i_mutex);
-		if (killpriv)
-			err = security_inode_killpriv(out->f_path.dentry);
-		if (!err && killsuid)
-			err = __remove_suid(out->f_path.dentry, killsuid);
-		mutex_unlock(&inode->i_mutex);
-		if (err)
-			return err;
-	}
 
-	ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
+	inode_double_lock(inode, pipe->inode);
+	ret = remove_suid(out->f_path.dentry);
+	if (likely(!ret))
+		ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
+	inode_double_unlock(inode, pipe->inode);
 	if (ret > 0) {
 		unsigned long nr_pages;
 
@@ -840,6 +835,8 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 		 * 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);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7e0fa9e64479..f413085f748e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1816,7 +1816,6 @@ extern void iget_failed(struct inode *);
 extern void clear_inode(struct inode *);
 extern void destroy_inode(struct inode *);
 extern struct inode *new_inode(struct super_block *);
-extern int __remove_suid(struct dentry *, int);
 extern int should_remove_suid(struct dentry *);
 extern int remove_suid(struct dentry *);
 
diff --git a/mm/filemap.c b/mm/filemap.c
index 239d36163bbe..2dead9adf8b7 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1655,7 +1655,7 @@ int should_remove_suid(struct dentry *dentry)
 }
 EXPORT_SYMBOL(should_remove_suid);
 
-int __remove_suid(struct dentry *dentry, int kill)
+static int __remove_suid(struct dentry *dentry, int kill)
 {
 	struct iattr newattrs;