#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/namei.h>
+#include <linux/slab.h>
#include <linux/mount.h>
#include <linux/tty.h>
#include <linux/mutex.h>
+#include <linux/magic.h>
#include <linux/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
#include <linux/seq_file.h>
-#define DEVPTS_SUPER_MAGIC 0x1cd1
-
#define DEVPTS_DEFAULT_MODE 0600
/*
* ptmx is a new node in /dev/pts and will be unused in legacy (single-
#define PARSE_MOUNT 0
#define PARSE_REMOUNT 1
+/*
+ * parse_mount_options():
+ * Set @opts to mount options specified in @data. If an option is not
+ * specified in @data, set it to its default value. The exception is
+ * 'newinstance' option which can only be set/cleared on a mount (i.e.
+ * cannot be changed during remount).
+ *
+ * Note: @data may be NULL (in which case all options are set to default).
+ */
static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
{
char *p;
}
/*
- * Safely parse the mount options in @data and update @opts.
+ * devpts_get_sb()
*
- * devpts ends up parsing options two times during mount, due to the
- * two modes of operation it supports. The first parse occurs in
- * devpts_get_sb() when determining the mode (single-instance or
- * multi-instance mode). The second parse happens in devpts_remount()
- * or new_pts_mount() depending on the mode.
+ * 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.
*
- * Parsing of options modifies the @data making subsequent parsing
- * incorrect. So make a local copy of @data and parse it.
+ * 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.
*
- * Return: 0 On success, -errno on error
- */
-static int safe_parse_mount_options(void *data, struct pts_mount_opts *opts)
-{
- int rc;
- void *datacp;
-
- if (!data)
- return 0;
-
- /* Use kstrdup() ? */
- datacp = kmalloc(PAGE_SIZE, GFP_KERNEL);
- if (!datacp)
- return -ENOMEM;
-
- memcpy(datacp, data, PAGE_SIZE);
- rc = parse_mount_options((char *)datacp, PARSE_MOUNT, opts);
- kfree(datacp);
-
- return rc;
-}
-
-/*
- * Mount a new (private) instance of devpts. PTYs created in this
- * instance are independent of the PTYs in other devpts instances.
- */
-static int new_pts_mount(struct file_system_type *fs_type, int flags,
- void *data, struct vfsmount *mnt)
-{
- int err;
- struct pts_fs_info *fsi;
- struct pts_mount_opts *opts;
-
- err = get_sb_nodev(fs_type, flags, data, devpts_fill_super, mnt);
- if (err)
- return err;
-
- fsi = DEVPTS_SB(mnt->mnt_sb);
- opts = &fsi->mount_opts;
-
- err = parse_mount_options(data, PARSE_MOUNT, opts);
- if (err)
- goto fail;
-
- err = mknod_ptmx(mnt->mnt_sb);
- if (err)
- goto fail;
-
- return 0;
-
-fail:
- dput(mnt->mnt_sb->s_root);
- up_write(&mnt->mnt_sb->s_umount);
- deactivate_super(mnt->mnt_sb);
- return err;
-}
-
-/*
- * Check if 'newinstance' mount option was specified in @data.
+ * 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 get_sb_single().
*
- * Return: -errno on error (eg: invalid mount options specified)
- * : 1 if 'newinstance' mount option was specified
- * : 0 if 'newinstance' mount option was NOT specified
- */
-static int is_new_instance_mount(void *data)
-{
- int rc;
- struct pts_mount_opts opts;
-
- if (!data)
- return 0;
-
- rc = safe_parse_mount_options(data, &opts);
- if (!rc)
- rc = opts.newinstance;
-
- return rc;
-}
-
-/*
- * get_init_pts_sb()
- *
- * This interface 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
- * get_sb_single().
+ * Mounts with 'newinstance' option create a new, private namespace.
*
- * Mounts with 'newinstance' option create a new private namespace.
+ * NOTE:
*
- * But for single-mount semantics, devpts cannot use get_sb_single(),
+ * For single-mount semantics, devpts cannot use get_sb_single(),
* because get_sb_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 get_sb_single() would pick the newinstance
* super-block instead of the initial super-block.
- *
- * This interface is identical to get_sb_single() except that it
- * consistently selects the 'single-namespace' superblock even in the
- * presence of the private namespace (i.e 'newinstance') super-blocks.
*/
-static int get_init_pts_sb(struct file_system_type *fs_type, int flags,
- void *data, struct vfsmount *mnt)
+static int devpts_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
- struct super_block *s;
int error;
+ struct pts_mount_opts opts;
+ struct super_block *s;
+
+ error = parse_mount_options(data, PARSE_MOUNT, &opts);
+ if (error)
+ return error;
+
+ if (opts.newinstance)
+ s = sget(fs_type, NULL, set_anon_super, NULL);
+ else
+ s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
- s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
if (IS_ERR(s))
return PTR_ERR(s);
if (!s->s_root) {
s->s_flags = flags;
error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
- if (error) {
- up_write(&s->s_umount);
- deactivate_super(s);
- return error;
- }
+ if (error)
+ goto out_undo_sget;
s->s_flags |= MS_ACTIVE;
}
- do_remount_sb(s, flags, data, 0);
- simple_set_mnt(mnt, s);
- return 0;
-}
-
-/*
- * Mount or remount the initial kernel mount of devpts. This type of
- * mount maintains the legacy, single-instance semantics, while the
- * kernel still allows multiple-instances.
- */
-static int init_pts_mount(struct file_system_type *fs_type, int flags,
- void *data, struct vfsmount *mnt)
-{
- int err;
-
- err = get_init_pts_sb(fs_type, flags, data, mnt);
- if (err)
- return err;
-
- err = mknod_ptmx(mnt->mnt_sb);
- if (err) {
- dput(mnt->mnt_sb->s_root);
- up_write(&mnt->mnt_sb->s_umount);
- deactivate_super(mnt->mnt_sb);
- }
- return err;
-}
+ memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
-static int devpts_get_sb(struct file_system_type *fs_type,
- int flags, const char *dev_name, void *data, struct vfsmount *mnt)
-{
- int new;
+ error = mknod_ptmx(s);
+ if (error)
+ goto out_undo_sget;
- new = is_new_instance_mount(data);
- if (new < 0)
- return new;
+ simple_set_mnt(mnt, s);
- if (new)
- return new_pts_mount(fs_type, flags, data, mnt);
+ return 0;
- return init_pts_mount(fs_type, flags, data, mnt);
+out_undo_sget:
+ deactivate_locked_super(s);
+ return error;
}
+
#else
/*
* This supports only the legacy single-instance semantics (no
}
static struct file_system_type devpts_fs_type = {
- .owner = THIS_MODULE,
.name = "devpts",
.get_sb = devpts_get_sb,
.kill_sb = devpts_kill_sb,
struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
{
+ struct dentry *dentry;
+ struct tty_struct *tty;
+
BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
+ /* Ensure dentry has not been deleted by devpts_pty_kill() */
+ dentry = d_find_alias(pts_inode);
+ if (!dentry)
+ return NULL;
+
+ tty = NULL;
if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
- return (struct tty_struct *)pts_inode->i_private;
- return NULL;
+ tty = (struct tty_struct *)pts_inode->i_private;
+
+ dput(dentry);
+
+ return tty;
}
void devpts_pty_kill(struct tty_struct *tty)
int err = register_filesystem(&devpts_fs_type);
if (!err) {
devpts_mnt = kern_mount(&devpts_fs_type);
- if (IS_ERR(devpts_mnt))
+ if (IS_ERR(devpts_mnt)) {
err = PTR_ERR(devpts_mnt);
+ unregister_filesystem(&devpts_fs_type);
+ }
}
return err;
}
-
-static void __exit exit_devpts_fs(void)
-{
- unregister_filesystem(&devpts_fs_type);
- mntput(devpts_mnt);
-}
-
module_init(init_devpts_fs)
-module_exit(exit_devpts_fs)
-MODULE_LICENSE("GPL");
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff