fs: move file_remove_suid() to fs/inode.c

file_remove_suid() is a generic function operates on struct file,
it almost has no relations with file mapping, so move it to fs/inode.c.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 65 insertions, 0 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 183ddd6cda71..a79555e492e0 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1530,6 +1530,71 @@ void touch_atime(struct path *path)
 }
 EXPORT_SYMBOL(touch_atime);
 
+/*
+ * The logic we want is
+ *
+ *      if suid or (sgid and xgrp)
+ *              remove privs
+ */
+int should_remove_suid(struct dentry *dentry)
+{
+        umode_t mode = dentry->d_inode->i_mode;
+        int kill = 0;
+
+        /* suid always must be killed */
+        if (unlikely(mode & S_ISUID))
+                kill = ATTR_KILL_SUID;
+
+        /*
+         * sgid without any exec bits is just a mandatory locking mark; leave
+         * it alone.  If some exec bits are set, it's a real sgid; kill it.
+         */
+        if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
+                kill |= ATTR_KILL_SGID;
+
+        if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
+                return kill;
+
+        return 0;
+}
+EXPORT_SYMBOL(should_remove_suid);
+
+static int __remove_suid(struct dentry *dentry, int kill)
+{
+        struct iattr newattrs;
+
+        newattrs.ia_valid = ATTR_FORCE | kill;
+        return notify_change(dentry, &newattrs);
+}
+
+int file_remove_suid(struct file *file)
+{
+        struct dentry *dentry = file->f_path.dentry;
+        struct inode *inode = dentry->d_inode;
+        int killsuid;
+        int killpriv;
+        int error = 0;
+
+        /* Fast path for nothing security related */
+        if (IS_NOSEC(inode))
+                return 0;
+
+        killsuid = should_remove_suid(dentry);
+        killpriv = security_inode_need_killpriv(dentry);
+
+        if (killpriv < 0)
+                return killpriv;
+        if (killpriv)
+                error = security_inode_killpriv(dentry);
+        if (!error && killsuid)
+                error = __remove_suid(dentry, killsuid);
+        if (!error && (inode->i_sb->s_flags & MS_NOSEC))
+                inode->i_flags |= S_NOSEC;
+
+        return error;
+}
+EXPORT_SYMBOL(file_remove_suid);
+
 /**
  *      file_update_time        -       update mtime and ctime time
  *      @file: file accessed