diff options
| author | Aleksa Sarai <asarai@suse.de> | 2017-06-04 00:15:15 +1000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-06-09 12:27:54 +0200 |
| commit | 54ebbfb1603415d9953c150535850d30609ef077 (patch) | |
| tree | edf8b41d6f34528641d97f2e5ee1fad5ea2df9c6 /arch/xtensa | |
| parent | 5f0f187fd0cc755cfa7d51b50f68a16fca41c813 (diff) | |
tty: add TIOCGPTPEER ioctl
When opening the slave end of a PTY, it is not possible for userspace to
safely ensure that /dev/pts/$num is actually a slave (in cases where the
mount namespace in which devpts was mounted is controlled by an
untrusted process). In addition, there are several unresolvable
race conditions if userspace were to attempt to detect attacks through
stat(2) and other similar methods [in addition it is not clear how
userspace could detect attacks involving FUSE].
Resolve this by providing an interface for userpace to safely open the
"peer" end of a PTY file descriptor by using the dentry cached by
devpts. Since it is not possible to have an open master PTY without
having its slave exposed in /dev/pts this interface is safe. This
interface currently does not provide a way to get the master pty (since
it is not clear whether such an interface is safe or even useful).
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Valentin Rothberg <vrothberg@suse.com>
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/xtensa')
| -rw-r--r-- | arch/xtensa/include/uapi/asm/ioctls.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/xtensa/include/uapi/asm/ioctls.h b/arch/xtensa/include/uapi/asm/ioctls.h index 518954e74e6d..98b004e24e85 100644 --- a/arch/xtensa/include/uapi/asm/ioctls.h +++ b/arch/xtensa/include/uapi/asm/ioctls.h @@ -105,6 +105,7 @@ #define TIOCGPKT _IOR('T', 0x38, int) /* Get packet mode state */ #define TIOCGPTLCK _IOR('T', 0x39, int) /* Get Pty lock state */ #define TIOCGEXCL _IOR('T', 0x40, int) /* Get exclusive mode state */ +#define TIOCGPTPEER _IOR('T', 0x41, int) /* Safely open the slave */ #define TIOCSERCONFIG _IO('T', 83) #define TIOCSERGWILD _IOR('T', 84, int) |