linux-kernel - [PATCH 4.7 090/184] devpts: return NULL pts priv entry for non-devpts nodes

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Message-Id: <20160922174052.559989080@linuxfoundation.org>
Date:   Thu, 22 Sep 2016 19:40:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
        "Eric W Biederman" <ebiederm@...ssion.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.7 090/184] devpts: return NULL pts priv entry for non-devpts nodes

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@...ux-foundation.org>

commit 3e423945ea94412283eaba8bfbe9d6e0a80b434f upstream.

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@...gle.com>
Cc: "Eric W Biederman" <ebiederm@...ssion.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/devpts/inode.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -584,7 +584,8 @@ struct dentry *devpts_pty_new(struct pts
  */
 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;
 }