devpts: return NULL pts 'priv' entry for non-devpts nodes

In commit 8ead9dd54716 ("devpts: more pty driver interface cleanups") I
made devpts_get_priv() just return the dentry->fs_data directly.  And
because I thought it wouldn't happen, I added a warning if you ever saw
a pts node that wasn't on devpts.

And no, that warning never triggered under any actual real use, but you
can trigger it by creating nonsensical pts nodes by hand.

So just revert the warning, and make devpts_get_priv() return NULL for
that case like it used to.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: stable@vger.kernel.org # 4.6+
Cc: Eric W Biederman" <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index d116453b0276634fabb32ee96df9cf96ce9cb25a..79a5941c2474622d7888c8e8c3bc925eabdb77e1 100644 (file)
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -585,7 +585,8 @@ struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
  */
 void *devpts_get_priv(struct dentry *dentry)
 {
-       WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);
+       if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
+               return NULL;
        return dentry->d_fsdata;
 }