#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-
+ * instance) mode. To prevent surprises in user space, set permissions of
+ * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
+ * permissions.
+ */
+#define DEVPTS_DEFAULT_PTMX_MODE 0000
#define PTMX_MINOR 2
extern int pty_limit; /* Config limit on Unix98 ptys */
static struct vfsmount *devpts_mnt;
-static struct {
+struct pts_mount_opts {
int setuid;
int setgid;
uid_t uid;
gid_t gid;
umode_t mode;
-} config = {.mode = DEVPTS_DEFAULT_MODE};
+ umode_t ptmxmode;
+ int newinstance;
+};
enum {
- Opt_uid, Opt_gid, Opt_mode,
+ Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
Opt_err
};
{Opt_uid, "uid=%u"},
{Opt_gid, "gid=%u"},
{Opt_mode, "mode=%o"},
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ {Opt_ptmxmode, "ptmxmode=%o"},
+ {Opt_newinstance, "newinstance"},
+#endif
{Opt_err, NULL}
};
struct pts_fs_info {
struct ida allocated_ptys;
+ struct pts_mount_opts mount_opts;
+ struct dentry *ptmx_dentry;
};
static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
static inline struct super_block *pts_sb_from_inode(struct inode *inode)
{
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
return inode->i_sb;
-
+#endif
return devpts_mnt->mnt_sb;
}
-static int devpts_remount(struct super_block *sb, int *flags, char *data)
+#define PARSE_MOUNT 0
+#define PARSE_REMOUNT 1
+
+static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
{
char *p;
- config.setuid = 0;
- config.setgid = 0;
- config.uid = 0;
- config.gid = 0;
- config.mode = DEVPTS_DEFAULT_MODE;
+ opts->setuid = 0;
+ opts->setgid = 0;
+ opts->uid = 0;
+ opts->gid = 0;
+ opts->mode = DEVPTS_DEFAULT_MODE;
+ opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
+
+ /* newinstance makes sense only on initial mount */
+ if (op == PARSE_MOUNT)
+ opts->newinstance = 0;
while ((p = strsep(&data, ",")) != NULL) {
substring_t args[MAX_OPT_ARGS];
case Opt_uid:
if (match_int(&args[0], &option))
return -EINVAL;
- config.uid = option;
- config.setuid = 1;
+ opts->uid = option;
+ opts->setuid = 1;
break;
case Opt_gid:
if (match_int(&args[0], &option))
return -EINVAL;
- config.gid = option;
- config.setgid = 1;
+ opts->gid = option;
+ opts->setgid = 1;
break;
case Opt_mode:
if (match_octal(&args[0], &option))
return -EINVAL;
- config.mode = option & S_IALLUGO;
+ opts->mode = option & S_IALLUGO;
+ break;
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ case Opt_ptmxmode:
+ if (match_octal(&args[0], &option))
+ return -EINVAL;
+ opts->ptmxmode = option & S_IALLUGO;
break;
+ case Opt_newinstance:
+ /* newinstance makes sense only on initial mount */
+ if (op == PARSE_MOUNT)
+ opts->newinstance = 1;
+ break;
+#endif
default:
printk(KERN_ERR "devpts: called with bogus options\n");
return -EINVAL;
return 0;
}
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+static int mknod_ptmx(struct super_block *sb)
+{
+ int mode;
+ int rc = -ENOMEM;
+ struct dentry *dentry;
+ struct inode *inode;
+ struct dentry *root = sb->s_root;
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+ struct pts_mount_opts *opts = &fsi->mount_opts;
+
+ mutex_lock(&root->d_inode->i_mutex);
+
+ /* If we have already created ptmx node, return */
+ if (fsi->ptmx_dentry) {
+ rc = 0;
+ goto out;
+ }
+
+ dentry = d_alloc_name(root, "ptmx");
+ if (!dentry) {
+ printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
+ goto out;
+ }
+
+ /*
+ * Create a new 'ptmx' node in this mount of devpts.
+ */
+ inode = new_inode(sb);
+ if (!inode) {
+ printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
+ dput(dentry);
+ goto out;
+ }
+
+ inode->i_ino = 2;
+ inode->i_uid = inode->i_gid = 0;
+ inode->i_blocks = 0;
+ inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+
+ mode = S_IFCHR|opts->ptmxmode;
+ init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+
+ d_add(dentry, inode);
+
+ fsi->ptmx_dentry = dentry;
+ rc = 0;
+
+ printk(KERN_DEBUG "Created ptmx node in devpts ino %lu\n",
+ inode->i_ino);
+out:
+ mutex_unlock(&root->d_inode->i_mutex);
+ return rc;
+}
+
+static void update_ptmx_mode(struct pts_fs_info *fsi)
+{
+ struct inode *inode;
+ if (fsi->ptmx_dentry) {
+ inode = fsi->ptmx_dentry->d_inode;
+ inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
+ }
+}
+#else
+static inline void update_ptmx_mode(struct pts_fs_info *fsi)
+{
+ return;
+}
+#endif
+
+static int devpts_remount(struct super_block *sb, int *flags, char *data)
+{
+ int err;
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+ struct pts_mount_opts *opts = &fsi->mount_opts;
+
+ err = parse_mount_options(data, PARSE_REMOUNT, opts);
+
+ /*
+ * parse_mount_options() restores options to default values
+ * before parsing and may have changed ptmxmode. So, update the
+ * mode in the inode too. Bogus options don't fail the remount,
+ * so do this even on error return.
+ */
+ update_ptmx_mode(fsi);
+
+ return err;
+}
+
static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
- if (config.setuid)
- seq_printf(seq, ",uid=%u", config.uid);
- if (config.setgid)
- seq_printf(seq, ",gid=%u", config.gid);
- seq_printf(seq, ",mode=%03o", config.mode);
+ struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
+ struct pts_mount_opts *opts = &fsi->mount_opts;
+
+ if (opts->setuid)
+ seq_printf(seq, ",uid=%u", opts->uid);
+ if (opts->setgid)
+ seq_printf(seq, ",gid=%u", opts->gid);
+ seq_printf(seq, ",mode=%03o", opts->mode);
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+#endif
return 0;
}
return NULL;
ida_init(&fsi->allocated_ptys);
+ fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
+ fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
return fsi;
}
static int
devpts_fill_super(struct super_block *s, void *data, int silent)
{
- struct inode * inode;
+ struct inode *inode;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_root = d_alloc_root(inode);
if (s->s_root)
return 0;
-
+
printk("devpts: get root dentry failed\n");
iput(inode);
return -ENOMEM;
}
+static int compare_init_pts_sb(struct super_block *s, void *p)
+{
+ if (devpts_mnt)
+ return devpts_mnt->mnt_sb == s;
+ return 0;
+}
+
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+/*
+ * Safely parse the mount options in @data and update @opts.
+ *
+ * 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.
+ *
+ * Parsing of options modifies the @data making subsequent parsing
+ * incorrect. So make a local copy of @data and parse it.
+ *
+ * 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;
+
+ printk(KERN_NOTICE "devpts: newinstance mount\n");
+
+ 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);
+ deactivate_super(mnt->mnt_sb);
+ return err;
+}
+
+/*
+ * Check if 'newinstance' mount option was specified in @data.
+ *
+ * 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.
+ *
+ * But 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)
+{
+ struct super_block *s;
+ int error;
+
+ 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;
+ }
+ s->s_flags |= MS_ACTIVE;
+ }
+ do_remount_sb(s, flags, data, 0);
+ return simple_set_mnt(mnt, s);
+}
+
+/*
+ * 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);
+ deactivate_super(mnt->mnt_sb);
+ }
+
+ return err;
+}
+
static int devpts_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
+{
+ int new;
+
+ new = is_new_instance_mount(data);
+ if (new < 0)
+ return new;
+
+ if (new)
+ return new_pts_mount(fs_type, flags, data, mnt);
+
+ return init_pts_mount(fs_type, flags, data, mnt);
+}
+#else
+/*
+ * This supports only the legacy single-instance semantics (no
+ * multiple-instance semantics)
+ */
+static int devpts_get_sb(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *data, struct vfsmount *mnt)
{
return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
}
+#endif
static void devpts_kill_sb(struct super_block *sb)
{
struct pts_fs_info *fsi = DEVPTS_SB(sb);
kfree(fsi);
- kill_anon_super(sb);
+ kill_litter_super(sb);
}
static struct file_system_type devpts_fs_type = {
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct inode *inode = new_inode(sb);
struct dentry *root = sb->s_root;
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+ struct pts_mount_opts *opts = &fsi->mount_opts;
char s[12];
/* We're supposed to be given the slave end of a pty */
inode->i_uid = config.setuid ? config.uid : current_fsuid();
inode->i_gid = config.setgid ? config.gid : current_fsgid();
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
- init_special_inode(inode, S_IFCHR|config.mode, device);
+ init_special_inode(inode, S_IFCHR|opts->mode, device);
inode->i_private = tty;
tty->driver_data = inode;
mutex_lock(&root->d_inode->i_mutex);
dentry = d_find_alias(inode);
- if (dentry && !IS_ERR(dentry)) {
+ if (IS_ERR(dentry))
+ goto out;
+
+ if (dentry) {
inode->i_nlink--;
d_delete(dentry);
- dput(dentry);
+ dput(dentry); // d_alloc_name() in devpts_pty_new()
}
+ dput(dentry); // d_find_alias above
+
+out:
mutex_unlock(&root->d_inode->i_mutex);
}
projects / firefly-linux-kernel-4.4.55.git / blobdiff