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From: Christian Brauner <christian.brauner@ubuntu.com>
To: libc-alpha@sourceware.org, stgraber@stgraber.org, serge@hallyn.com
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Subject: [PATCH 2/2] openpty: use TIOCGPTPEER to open slave side fd
Date: Sat, 26 Aug 2017 14:21:00 -0000	[thread overview]
Message-ID: <20170826134449.26527-2-christian.brauner@ubuntu.com> (raw)
In-Reply-To: <20170826134449.26527-1-christian.brauner@ubuntu.com>

Newer kernels expose the ioctl TIOCGPTPEER [1] call to userspace which allows to
safely allocate a file descriptor for a pty slave based solely on the master
file descriptor. This allows us to avoid path-based operations and makes this
function a lot safer in the face of devpts mounts in different mount namespaces.

[1]: https://patchwork.kernel.org/patch/9760743/

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
 ChangeLog       |  5 +++++
 login/openpty.c | 12 +++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index bc5fb8e27f..30829e4c16 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-08-26  Christian Brauner  <christian.brauner@ubuntu.com>
+
+	* login/openpty.c (openpty): If defined, use the TIOCGPTPEER ioctl call
+	to allocate the slave pty file descriptor.
+
 2017-08-26  Christian Brauner  <christian.brauner@ubuntu.com>
 
 	* login/openpty.c (openpty): Close slave pty file descriptor on error.
diff --git a/login/openpty.c b/login/openpty.c
index 8fbc66a3ef..293cc0a0db 100644
--- a/login/openpty.c
+++ b/login/openpty.c
@@ -104,10 +104,14 @@ openpty (int *amaster, int *aslave, char *name,
   if (unlockpt (master))
     goto fail;
 
+#ifdef TIOCGPTPEER
+  slave = ioctl (master, TIOCGPTPEER, O_RDWR | O_NOCTTY);
+#else
   if (pts_name (master, &buf, sizeof (_buf)))
     goto fail;
 
   slave = open (buf, O_RDWR | O_NOCTTY);
+#endif
   if (slave == -1)
     {
       if (buf != _buf)
@@ -127,7 +131,13 @@ openpty (int *amaster, int *aslave, char *name,
   *amaster = master;
   *aslave = slave;
   if (name != NULL)
-    strcpy (name, buf);
+    {
+#ifdef TIOCGPTPEER
+      if (pts_name (master, &buf, sizeof (_buf)))
+        goto fail;
+#endif
+      strcpy (name, buf);
+    }
 
   if (buf != _buf)
     free (buf);
-- 
2.14.1

  reply	other threads:[~2017-08-26 14:21 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-26 14:21 [PATCH 1/2] openpty: close slave pty fd on error Christian Brauner
2017-08-26 14:21 ` Christian Brauner [this message]
2017-08-28  7:34   ` [PATCH 2/2] openpty: use TIOCGPTPEER to open slave side fd Florian Weimer
2017-08-28 11:14     ` Christian Brauner
2017-08-28 11:39     ` Joseph Myers
2017-08-28 12:11     ` [PATCH 2/2 v2] " Christian Brauner
2017-08-28 12:22       ` Joseph Myers
2017-08-28 12:34       ` Andreas Schwab
2017-08-28 12:51         ` [PATCH 2/2 v3] " Christian Brauner
2017-08-29  9:07 ` [PATCH 1/2] openpty: close slave pty fd on error Florian Weimer
2017-08-29 13:46   ` [PATCH 1/2 v4] " Christian Brauner
2017-08-29 13:46     ` [PATCH 2/2 v4] openpty: use TIOCGPTPEER to open slave side fd Christian Brauner
2017-08-29 14:00     ` [PATCH 1/2 v4] openpty: close slave pty fd on error Andreas Schwab
2017-08-29 14:12       ` Christian Brauner
2017-08-29 14:31       ` [PATCH 1/2 v5] " Christian Brauner
2017-08-29 14:31         ` [PATCH 2/2 v5] openpty: use TIOCGPTPEER to open slave side fd Christian Brauner
2017-09-10 17:45         ` [PATCH 1/2 v5] openpty: close slave pty fd on error Christian Brauner
2017-09-20 10:53           ` Christian Brauner

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