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devpts: Make each mount of devpts an independent filesystem.
The /dev/ptmx device node is changed to lookup the directory entry "pts" in the same directory as the /dev/ptmx device node was opened in. If there is a "pts" entry and that entry is a devpts filesystem /dev/ptmx uses that filesystem. Otherwise the open of /dev/ptmx fails. The DEVPTS_MULTIPLE_INSTANCES configuration option is removed, so that userspace can now safely depend on each mount of devpts creating a new instance of the filesystem. Each mount of devpts is now a separate and equal filesystem. Reserved ttys are now available to all instances of devpts where the mounter is in the initial mount namespace. A new vfs helper path_pts is introduced that finds a directory entry named "pts" in the directory of the passed in path, and changes the passed in path to point to it. The helper path_pts uses a function path_parent_directory that was factored out of follow_dotdot. In the implementation of devpts: - devpts_mnt is killed as it is no longer meaningful if all mounts of devpts are equal. - pts_sb_from_inode is replaced by just inode->i_sb as all cached inodes in the tty layer are now from the devpts filesystem. - devpts_add_ref is rolled into the new function devpts_ptmx. And the unnecessary inode hold is removed. - devpts_del_ref is renamed devpts_release and reduced to just a deacrivate_super. - The newinstance mount option continues to be accepted but is now ignored. In devpts_fs.h definitions for when !CONFIG_UNIX98_PTYS are removed as they are never used. Documentation/filesystems/devices.txt is updated to describe the current situation. This has been verified to work properly on openwrt-15.05, centos5, centos6, centos7, debian-6.0.2, debian-7.9, debian-8.2, ubuntu-14.04.3, ubuntu-15.10, fedora23, magia-5, mint-17.3, opensuse-42.1, slackware-14.1, gentoo-20151225 (13.0?), archlinux-2015-12-01. With the caveat that on centos6 and on slackware-14.1 that there wind up being two instances of the devpts filesystem mounted on /dev/pts, the lower copy does not end up getting used. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Greg KH <greg@kroah.com> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Peter Anvin <hpa@zytor.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Serge Hallyn <serge.hallyn@ubuntu.com> Cc: Willy Tarreau <w@1wt.eu> Cc: Aurelien Jarno <aurelien@aurel32.net> Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> Cc: Jann Horn <jann@thejh.net> Cc: Jiri Slaby <jslaby@suse.com> Cc: Florian Weimer <fw@deneb.enyo.de> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric W. Biederman
Linus Torvalds
parent
049ec1b5a7
commit
eedf265aa0
@ -1,141 +1,26 @@
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Each mount of the devpts filesystem is now distinct such that ptys
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and their indicies allocated in one mount are independent from ptys
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and their indicies in all other mounts.
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To support containers, we now allow multiple instances of devpts filesystem,
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such that indices of ptys allocated in one instance are independent of indices
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allocated in other instances of devpts.
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All mounts of the devpts filesystem now create a /dev/pts/ptmx node
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with permissions 0000.
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To preserve backward compatibility, this support for multiple instances is
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enabled only if:
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To retain backwards compatibility the a ptmx device node (aka any node
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created with "mknod name c 5 2") when opened will look for an instance
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of devpts under the name "pts" in the same directory as the ptmx device
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node.
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- CONFIG_DEVPTS_MULTIPLE_INSTANCES=y, and
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- '-o newinstance' mount option is specified while mounting devpts
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IOW, devpts now supports both single-instance and multi-instance semantics.
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If CONFIG_DEVPTS_MULTIPLE_INSTANCES=n, there is no change in behavior and
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this referred to as the "legacy" mode. In this mode, the new mount options
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(-o newinstance and -o ptmxmode) will be ignored with a 'bogus option' message
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on console.
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If CONFIG_DEVPTS_MULTIPLE_INSTANCES=y and devpts is mounted without the
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'newinstance' option (as in current start-up scripts) the new mount binds
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to the initial kernel mount of devpts. This mode is referred to as the
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'single-instance' mode and the current, single-instance semantics are
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preserved, i.e PTYs are common across the system.
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The only difference between this single-instance mode and the legacy mode
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is the presence of new, '/dev/pts/ptmx' node with permissions 0000, which
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can safely be ignored.
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If CONFIG_DEVPTS_MULTIPLE_INSTANCES=y and 'newinstance' option is specified,
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the mount is considered to be in the multi-instance mode and a new instance
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of the devpts fs is created. Any ptys created in this instance are independent
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of ptys in other instances of devpts. Like in the single-instance mode, the
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/dev/pts/ptmx node is present. To effectively use the multi-instance mode,
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open of /dev/ptmx must be a redirected to '/dev/pts/ptmx' using a symlink or
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bind-mount.
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Eg: A container startup script could do the following:
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$ chmod 0666 /dev/pts/ptmx
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$ rm /dev/ptmx
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$ ln -s pts/ptmx /dev/ptmx
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$ ns_exec -cm /bin/bash
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# We are now in new container
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$ umount /dev/pts
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$ mount -t devpts -o newinstance lxcpts /dev/pts
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$ sshd -p 1234
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where 'ns_exec -cm /bin/bash' calls clone() with CLONE_NEWNS flag and execs
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/bin/bash in the child process. A pty created by the sshd is not visible in
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the original mount of /dev/pts.
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As an option instead of placing a /dev/ptmx device node at /dev/ptmx
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it is possible to place a symlink to /dev/pts/ptmx at /dev/ptmx or
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to bind mount /dev/ptx/ptmx to /dev/ptmx. If you opt for using
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the devpts filesystem in this manner devpts should be mounted with
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the ptmxmode=0666, or chmod 0666 /dev/pts/ptmx should be called.
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Total count of pty pairs in all instances is limited by sysctls:
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kernel.pty.max = 4096 - global limit
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kernel.pty.reserve = 1024 - reserve for initial instance
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kernel.pty.reserve = 1024 - reserved for filesystems mounted from the initial mount namespace
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kernel.pty.nr - current count of ptys
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Per-instance limit could be set by adding mount option "max=<count>".
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This feature was added in kernel 3.4 together with sysctl kernel.pty.reserve.
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In kernels older than 3.4 sysctl kernel.pty.max works as per-instance limit.
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User-space changes
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------------------
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In multi-instance mode (i.e '-o newinstance' mount option is specified at least
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once), following user-space issues should be noted.
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1. If -o newinstance mount option is never used, /dev/pts/ptmx can be ignored
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and no change is needed to system-startup scripts.
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2. To effectively use multi-instance mode (i.e -o newinstance is specified)
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administrators or startup scripts should "redirect" open of /dev/ptmx to
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/dev/pts/ptmx using either a bind mount or symlink.
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$ mount -t devpts -o newinstance devpts /dev/pts
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followed by either
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$ rm /dev/ptmx
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$ ln -s pts/ptmx /dev/ptmx
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$ chmod 666 /dev/pts/ptmx
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or
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$ mount -o bind /dev/pts/ptmx /dev/ptmx
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3. The '/dev/ptmx -> pts/ptmx' symlink is the preferred method since it
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enables better error-reporting and treats both single-instance and
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multi-instance mounts similarly.
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But this method requires that system-startup scripts set the mode of
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/dev/pts/ptmx correctly (default mode is 0000). The scripts can set the
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mode by, either
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- adding ptmxmode mount option to devpts entry in /etc/fstab, or
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- using 'chmod 0666 /dev/pts/ptmx'
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4. If multi-instance mode mount is needed for containers, but the system
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startup scripts have not yet been updated, container-startup scripts
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should bind mount /dev/ptmx to /dev/pts/ptmx to avoid breaking single-
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instance mounts.
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Or, in general, container-startup scripts should use:
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mount -t devpts -o newinstance -o ptmxmode=0666 devpts /dev/pts
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if [ ! -L /dev/ptmx ]; then
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mount -o bind /dev/pts/ptmx /dev/ptmx
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fi
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When all devpts mounts are multi-instance, /dev/ptmx can permanently be
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a symlink to pts/ptmx and the bind mount can be ignored.
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5. A multi-instance mount that is not accompanied by the /dev/ptmx to
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/dev/pts/ptmx redirection would result in an unusable/unreachable pty.
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mount -t devpts -o newinstance lxcpts /dev/pts
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immediately followed by:
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open("/dev/ptmx")
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would create a pty, say /dev/pts/7, in the initial kernel mount.
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But /dev/pts/7 would be invisible in the new mount.
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6. The permissions for /dev/pts/ptmx node should be specified when mounting
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/dev/pts, using the '-o ptmxmode=%o' mount option (default is 0000).
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mount -t devpts -o newinstance -o ptmxmode=0644 devpts /dev/pts
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The permissions can be later be changed as usual with 'chmod'.
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chmod 666 /dev/pts/ptmx
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7. A mount of devpts without the 'newinstance' option results in binding to
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initial kernel mount. This behavior while preserving legacy semantics,
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does not provide strict isolation in a container environment. i.e by
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mounting devpts without the 'newinstance' option, a container could
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get visibility into the 'host' or root container's devpts.
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To workaround this and have strict isolation, all mounts of devpts,
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including the mount in the root container, should use the newinstance
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option.
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@ -120,17 +120,6 @@ config UNIX98_PTYS
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All modern Linux systems use the Unix98 ptys. Say Y unless
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you're on an embedded system and want to conserve memory.
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config DEVPTS_MULTIPLE_INSTANCES
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bool "Support multiple instances of devpts"
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depends on UNIX98_PTYS
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default n
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---help---
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Enable support for multiple instances of devpts filesystem.
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If you want to have isolated PTY namespaces (eg: in containers),
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say Y here. Otherwise, say N. If enabled, each mount of devpts
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filesystem with the '-o newinstance' option will create an
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independent PTY namespace.
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config LEGACY_PTYS
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bool "Legacy (BSD) PTY support"
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default y
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@ -668,7 +668,7 @@ static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
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else
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fsi = tty->link->driver_data;
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devpts_kill_index(fsi, tty->index);
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devpts_put_ref(fsi);
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devpts_release(fsi);
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}
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static const struct tty_operations ptm_unix98_ops = {
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@ -733,10 +733,11 @@ static int ptmx_open(struct inode *inode, struct file *filp)
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if (retval)
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return retval;
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fsi = devpts_get_ref(inode, filp);
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retval = -ENODEV;
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if (!fsi)
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fsi = devpts_acquire(filp);
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if (IS_ERR(fsi)) {
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retval = PTR_ERR(fsi);
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goto out_free_file;
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}
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/* find a device that is not in use. */
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mutex_lock(&devpts_mutex);
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@ -745,7 +746,7 @@ static int ptmx_open(struct inode *inode, struct file *filp)
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retval = index;
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if (index < 0)
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goto out_put_ref;
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goto out_put_fsi;
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mutex_lock(&tty_mutex);
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@ -789,8 +790,8 @@ err_release:
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return retval;
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out:
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devpts_kill_index(fsi, index);
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out_put_ref:
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devpts_put_ref(fsi);
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out_put_fsi:
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devpts_release(fsi);
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out_free_file:
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tty_free_file(filp);
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return retval;
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@ -95,8 +95,6 @@ static struct ctl_table pty_root_table[] = {
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static DEFINE_MUTEX(allocated_ptys_lock);
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static struct vfsmount *devpts_mnt;
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struct pts_mount_opts {
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int setuid;
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int setgid;
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@ -104,7 +102,7 @@ struct pts_mount_opts {
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kgid_t gid;
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umode_t mode;
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umode_t ptmxmode;
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int newinstance;
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int reserve;
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int max;
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};
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@ -117,11 +115,9 @@ static const match_table_t tokens = {
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{Opt_uid, "uid=%u"},
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{Opt_gid, "gid=%u"},
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{Opt_mode, "mode=%o"},
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#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
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{Opt_ptmxmode, "ptmxmode=%o"},
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{Opt_newinstance, "newinstance"},
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{Opt_max, "max=%d"},
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#endif
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{Opt_err, NULL}
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};
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@ -137,15 +133,48 @@ static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
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return sb->s_fs_info;
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}
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static inline struct super_block *pts_sb_from_inode(struct inode *inode)
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struct pts_fs_info *devpts_acquire(struct file *filp)
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{
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#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
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if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
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return inode->i_sb;
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#endif
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if (!devpts_mnt)
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return NULL;
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return devpts_mnt->mnt_sb;
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struct pts_fs_info *result;
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struct path path;
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struct super_block *sb;
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int err;
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path = filp->f_path;
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path_get(&path);
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/* Has the devpts filesystem already been found? */
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sb = path.mnt->mnt_sb;
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if (sb->s_magic != DEVPTS_SUPER_MAGIC) {
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/* Is a devpts filesystem at "pts" in the same directory? */
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err = path_pts(&path);
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if (err) {
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result = ERR_PTR(err);
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goto out;
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}
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/* Is the path the root of a devpts filesystem? */
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result = ERR_PTR(-ENODEV);
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sb = path.mnt->mnt_sb;
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if ((sb->s_magic != DEVPTS_SUPER_MAGIC) ||
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(path.mnt->mnt_root != sb->s_root))
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goto out;
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}
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/*
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* pty code needs to hold extra references in case of last /dev/tty close
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*/
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atomic_inc(&sb->s_active);
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result = DEVPTS_SB(sb);
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out:
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path_put(&path);
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return result;
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}
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void devpts_release(struct pts_fs_info *fsi)
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{
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deactivate_super(fsi->sb);
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}
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#define PARSE_MOUNT 0
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@ -154,9 +183,7 @@ static inline struct super_block *pts_sb_from_inode(struct inode *inode)
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/*
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* parse_mount_options():
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* Set @opts to mount options specified in @data. If an option is not
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* specified in @data, set it to its default value. The exception is
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* 'newinstance' option which can only be set/cleared on a mount (i.e.
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* cannot be changed during remount).
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* specified in @data, set it to its default value.
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*
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* Note: @data may be NULL (in which case all options are set to default).
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*/
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@ -174,9 +201,12 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
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opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
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opts->max = NR_UNIX98_PTY_MAX;
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/* newinstance makes sense only on initial mount */
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/* Only allow instances mounted from the initial mount
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* namespace to tap the reserve pool of ptys.
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*/
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if (op == PARSE_MOUNT)
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opts->newinstance = 0;
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opts->reserve =
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(current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);
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while ((p = strsep(&data, ",")) != NULL) {
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substring_t args[MAX_OPT_ARGS];
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@ -211,16 +241,12 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
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return -EINVAL;
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opts->mode = option & S_IALLUGO;
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break;
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#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
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case Opt_ptmxmode:
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if (match_octal(&args[0], &option))
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return -EINVAL;
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opts->ptmxmode = option & S_IALLUGO;
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break;
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case Opt_newinstance:
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/* newinstance makes sense only on initial mount */
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if (op == PARSE_MOUNT)
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opts->newinstance = 1;
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break;
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case Opt_max:
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if (match_int(&args[0], &option) ||
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@ -228,7 +254,6 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
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return -EINVAL;
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opts->max = option;
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break;
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#endif
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default:
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pr_err("called with bogus options\n");
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return -EINVAL;
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@ -238,7 +263,6 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
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return 0;
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}
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#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
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static int mknod_ptmx(struct super_block *sb)
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{
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int mode;
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@ -305,12 +329,6 @@ static void update_ptmx_mode(struct pts_fs_info *fsi)
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inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
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}
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}
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#else
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static inline void update_ptmx_mode(struct pts_fs_info *fsi)
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{
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return;
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}
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#endif
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static int devpts_remount(struct super_block *sb, int *flags, char *data)
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{
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@ -344,11 +362,9 @@ static int devpts_show_options(struct seq_file *seq, struct dentry *root)
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seq_printf(seq, ",gid=%u",
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from_kgid_munged(&init_user_ns, opts->gid));
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seq_printf(seq, ",mode=%03o", opts->mode);
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#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
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seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
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if (opts->max < NR_UNIX98_PTY_MAX)
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seq_printf(seq, ",max=%d", opts->max);
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#endif
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return 0;
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}
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@ -410,40 +426,11 @@ fail:
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return -ENOMEM;
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}
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#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
|
||||
static int compare_init_pts_sb(struct super_block *s, void *p)
|
||||
{
|
||||
if (devpts_mnt)
|
||||
return devpts_mnt->mnt_sb == s;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* devpts_mount()
|
||||
*
|
||||
* If the '-o newinstance' mount option was specified, mount a new
|
||||
* (private) instance of devpts. PTYs created in this instance are
|
||||
* independent of the PTYs in other devpts instances.
|
||||
*
|
||||
* If the '-o newinstance' option was not specified, mount/remount the
|
||||
* initial kernel mount of devpts. This type of mount gives the
|
||||
* legacy, single-instance semantics.
|
||||
*
|
||||
* The 'newinstance' option is needed to support multiple namespace
|
||||
* semantics in devpts while preserving backward compatibility of the
|
||||
* current 'single-namespace' semantics. i.e all mounts of devpts
|
||||
* without the 'newinstance' mount option should bind to the initial
|
||||
* kernel mount, like mount_single().
|
||||
*
|
||||
* Mounts with 'newinstance' option create a new, private namespace.
|
||||
*
|
||||
* NOTE:
|
||||
*
|
||||
* For single-mount semantics, devpts cannot use mount_single(),
|
||||
* because mount_single()/sget() find and use the super-block from
|
||||
* the most recent mount of devpts. But that recent mount may be a
|
||||
* 'newinstance' mount and mount_single() would pick the newinstance
|
||||
* super-block instead of the initial super-block.
|
||||
* Mount a new (private) instance of devpts. PTYs created in this
|
||||
* instance are independent of the PTYs in other devpts instances.
|
||||
*/
|
||||
static struct dentry *devpts_mount(struct file_system_type *fs_type,
|
||||
int flags, const char *dev_name, void *data)
|
||||
@ -456,18 +443,7 @@ static struct dentry *devpts_mount(struct file_system_type *fs_type,
|
||||
if (error)
|
||||
return ERR_PTR(error);
|
||||
|
||||
/* Require newinstance for all user namespace mounts to ensure
|
||||
* the mount options are not changed.
|
||||
*/
|
||||
if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
|
||||
return ERR_PTR(-EINVAL);
|
||||
|
||||
if (opts.newinstance)
|
||||
s = sget(fs_type, NULL, set_anon_super, flags, NULL);
|
||||
else
|
||||
s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags,
|
||||
NULL);
|
||||
|
||||
s = sget(fs_type, NULL, set_anon_super, flags, NULL);
|
||||
if (IS_ERR(s))
|
||||
return ERR_CAST(s);
|
||||
|
||||
@ -491,18 +467,6 @@ out_undo_sget:
|
||||
return ERR_PTR(error);
|
||||
}
|
||||
|
||||
#else
|
||||
/*
|
||||
* This supports only the legacy single-instance semantics (no
|
||||
* multiple-instance semantics)
|
||||
*/
|
||||
static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
|
||||
const char *dev_name, void *data)
|
||||
{
|
||||
return mount_single(fs_type, flags, data, devpts_fill_super);
|
||||
}
|
||||
#endif
|
||||
|
||||
static void devpts_kill_sb(struct super_block *sb)
|
||||
{
|
||||
struct pts_fs_info *fsi = DEVPTS_SB(sb);
|
||||
@ -516,9 +480,7 @@ static struct file_system_type devpts_fs_type = {
|
||||
.name = "devpts",
|
||||
.mount = devpts_mount,
|
||||
.kill_sb = devpts_kill_sb,
|
||||
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
|
||||
.fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
|
||||
#endif
|
||||
};
|
||||
|
||||
/*
|
||||
@ -531,16 +493,13 @@ int devpts_new_index(struct pts_fs_info *fsi)
|
||||
int index;
|
||||
int ida_ret;
|
||||
|
||||
if (!fsi)
|
||||
return -ENODEV;
|
||||
|
||||
retry:
|
||||
if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
|
||||
return -ENOMEM;
|
||||
|
||||
mutex_lock(&allocated_ptys_lock);
|
||||
if (pty_count >= pty_limit -
|
||||
(fsi->mount_opts.newinstance ? pty_reserve : 0)) {
|
||||
if (pty_count >= (pty_limit -
|
||||
(fsi->mount_opts.reserve ? 0 : pty_reserve))) {
|
||||
mutex_unlock(&allocated_ptys_lock);
|
||||
return -ENOSPC;
|
||||
}
|
||||
@ -571,30 +530,6 @@ void devpts_kill_index(struct pts_fs_info *fsi, int idx)
|
||||
mutex_unlock(&allocated_ptys_lock);
|
||||
}
|
||||
|
||||
/*
|
||||
* pty code needs to hold extra references in case of last /dev/tty close
|
||||
*/
|
||||
struct pts_fs_info *devpts_get_ref(struct inode *ptmx_inode, struct file *file)
|
||||
{
|
||||
struct super_block *sb;
|
||||
struct pts_fs_info *fsi;
|
||||
|
||||
sb = pts_sb_from_inode(ptmx_inode);
|
||||
if (!sb)
|
||||
return NULL;
|
||||
fsi = DEVPTS_SB(sb);
|
||||
if (!fsi)
|
||||
return NULL;
|
||||
|
||||
atomic_inc(&sb->s_active);
|
||||
return fsi;
|
||||
}
|
||||
|
||||
void devpts_put_ref(struct pts_fs_info *fsi)
|
||||
{
|
||||
deactivate_super(fsi->sb);
|
||||
}
|
||||
|
||||
/**
|
||||
* devpts_pty_new -- create a new inode in /dev/pts/
|
||||
* @ptmx_inode: inode of the master
|
||||
@ -607,16 +542,12 @@ void devpts_put_ref(struct pts_fs_info *fsi)
|
||||
struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
|
||||
{
|
||||
struct dentry *dentry;
|
||||
struct super_block *sb;
|
||||
struct super_block *sb = fsi->sb;
|
||||
struct inode *inode;
|
||||
struct dentry *root;
|
||||
struct pts_mount_opts *opts;
|
||||
char s[12];
|
||||
|
||||
if (!fsi)
|
||||
return ERR_PTR(-ENODEV);
|
||||
|
||||
sb = fsi->sb;
|
||||
root = sb->s_root;
|
||||
opts = &fsi->mount_opts;
|
||||
|
||||
@ -676,20 +607,8 @@ void devpts_pty_kill(struct dentry *dentry)
|
||||
static int __init init_devpts_fs(void)
|
||||
{
|
||||
int err = register_filesystem(&devpts_fs_type);
|
||||
struct ctl_table_header *table;
|
||||
|
||||
if (!err) {
|
||||
struct vfsmount *mnt;
|
||||
|
||||
table = register_sysctl_table(pty_root_table);
|
||||
mnt = kern_mount(&devpts_fs_type);
|
||||
if (IS_ERR(mnt)) {
|
||||
err = PTR_ERR(mnt);
|
||||
unregister_filesystem(&devpts_fs_type);
|
||||
unregister_sysctl_table(table);
|
||||
} else {
|
||||
devpts_mnt = mnt;
|
||||
}
|
||||
register_sysctl_table(pty_root_table);
|
||||
}
|
||||
return err;
|
||||
}
|
||||
|
||||
49
fs/namei.c
49
fs/namei.c
@ -1416,21 +1416,28 @@ static void follow_mount(struct path *path)
|
||||
}
|
||||
}
|
||||
|
||||
static int path_parent_directory(struct path *path)
|
||||
{
|
||||
struct dentry *old = path->dentry;
|
||||
/* rare case of legitimate dget_parent()... */
|
||||
path->dentry = dget_parent(path->dentry);
|
||||
dput(old);
|
||||
if (unlikely(!path_connected(path)))
|
||||
return -ENOENT;
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int follow_dotdot(struct nameidata *nd)
|
||||
{
|
||||
while(1) {
|
||||
struct dentry *old = nd->path.dentry;
|
||||
|
||||
if (nd->path.dentry == nd->root.dentry &&
|
||||
nd->path.mnt == nd->root.mnt) {
|
||||
break;
|
||||
}
|
||||
if (nd->path.dentry != nd->path.mnt->mnt_root) {
|
||||
/* rare case of legitimate dget_parent()... */
|
||||
nd->path.dentry = dget_parent(nd->path.dentry);
|
||||
dput(old);
|
||||
if (unlikely(!path_connected(&nd->path)))
|
||||
return -ENOENT;
|
||||
int ret = path_parent_directory(&nd->path);
|
||||
if (ret)
|
||||
return ret;
|
||||
break;
|
||||
}
|
||||
if (!follow_up(&nd->path))
|
||||
@ -2514,6 +2521,34 @@ struct dentry *lookup_one_len_unlocked(const char *name,
|
||||
}
|
||||
EXPORT_SYMBOL(lookup_one_len_unlocked);
|
||||
|
||||
#ifdef CONFIG_UNIX98_PTYS
|
||||
int path_pts(struct path *path)
|
||||
{
|
||||
/* Find something mounted on "pts" in the same directory as
|
||||
* the input path.
|
||||
*/
|
||||
struct dentry *child, *parent;
|
||||
struct qstr this;
|
||||
int ret;
|
||||
|
||||
ret = path_parent_directory(path);
|
||||
if (ret)
|
||||
return ret;
|
||||
|
||||
parent = path->dentry;
|
||||
this.name = "pts";
|
||||
this.len = 3;
|
||||
child = d_hash_and_lookup(parent, &this);
|
||||
if (!child)
|
||||
return -ENOENT;
|
||||
|
||||
path->dentry = child;
|
||||
dput(parent);
|
||||
follow_mount(path);
|
||||
return 0;
|
||||
}
|
||||
#endif
|
||||
|
||||
int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
|
||||
struct path *path, int *empty)
|
||||
{
|
||||
|
||||
@ -15,13 +15,12 @@
|
||||
|
||||
#include <linux/errno.h>
|
||||
|
||||
struct pts_fs_info;
|
||||
|
||||
#ifdef CONFIG_UNIX98_PTYS
|
||||
|
||||
/* Look up a pts fs info and get a ref to it */
|
||||
struct pts_fs_info *devpts_get_ref(struct inode *, struct file *);
|
||||
void devpts_put_ref(struct pts_fs_info *);
|
||||
struct pts_fs_info;
|
||||
|
||||
struct pts_fs_info *devpts_acquire(struct file *);
|
||||
void devpts_release(struct pts_fs_info *);
|
||||
|
||||
int devpts_new_index(struct pts_fs_info *);
|
||||
void devpts_kill_index(struct pts_fs_info *, int);
|
||||
|
||||
@ -45,6 +45,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
|
||||
#define LOOKUP_ROOT 0x2000
|
||||
#define LOOKUP_EMPTY 0x4000
|
||||
|
||||
extern int path_pts(struct path *path);
|
||||
|
||||
extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
|
||||
|
||||
static inline int user_path_at(int dfd, const char __user *name, unsigned flags,
|
||||
|
||||
Loading…
Reference in New Issue
Block a user