linux-kernel - [PATCH 08/16] devpts: Stop rolling devpts_remount by hand in devpts

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Date:	Fri, 15 Apr 2016 10:35:24 -0500
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>, security@...ian.org,
	security@...nel.org, Al Viro <viro@...iv.linux.org.uk>,
	security@...ntu.com, Peter Hurley <peter@...leysoftware.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Willy Tarreau <w@....eu>,
	Aurelien Jarno <aurelien@...el32.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jann Horn <jann@...jh.net>, Greg KH <greg@...ah.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.com>,
	Florian Weimer <fw@...eb.enyo.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 08/16] devpts: Stop rolling devpts_remount by hand in devpts_mount

Just use devpts_remount and by doing so ensuring that ptxmode
actually get propogated to /dev/pts/ptmx on the initial mount
of devpts.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/devpts/inode.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index d65be43b6fe9..1266abd3251e 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -249,12 +249,6 @@ static int mknod_ptmx(struct super_block *sb)
 
 	inode_lock(d_inode(root));
 
-	/* If we have already created ptmx node, return */
-	if (fsi->ptmx_dentry) {
-		rc = 0;
-		goto out;
-	}
-
 	dentry = d_alloc_name(root, "ptmx");
 	if (!dentry) {
 		pr_err("Unable to alloc dentry for ptmx node\n");
@@ -464,16 +458,20 @@ static struct dentry *devpts_mount(struct file_system_type *fs_type,
 		error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 		if (error)
 			goto out_undo_sget;
-		s->s_flags |= MS_ACTIVE;
-	}
 
-	error = parse_mount_options(data, &DEVPTS_SB(s)->mount_opts);
-	if (error)
-		goto out_undo_sget;
+		error = parse_mount_options(data, &DEVPTS_SB(s)->mount_opts);
+		if (error)
+			goto out_undo_sget;
+
+		error = mknod_ptmx(s);
+		if (error)
+			goto out_undo_sget;
 
-	error = mknod_ptmx(s);
-	if (error)
-		goto out_undo_sget;
+		s->s_flags |= MS_ACTIVE;
+	} else {
+		/* Match mount_single ignore errors on remount */
+		devpts_remount(s, &flags, data);
+	}
 
 	return dget(s->s_root);
 
-- 
2.8.1