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-rw-r--r--fs/devpts/inode.c619
1 files changed, 619 insertions, 0 deletions
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
new file mode 100644
index 0000000000..299c295a27
--- /dev/null
+++ b/fs/devpts/inode.c
@@ -0,0 +1,619 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* -*- linux-c -*- --------------------------------------------------------- *
+ *
+ * linux/fs/devpts/inode.c
+ *
+ * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
+ *
+ * ------------------------------------------------------------------------- */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#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_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
+
+/*
+ * sysctl support for setting limits on the number of Unix98 ptys allocated.
+ * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
+ */
+static int pty_limit = NR_UNIX98_PTY_DEFAULT;
+static int pty_reserve = NR_UNIX98_PTY_RESERVE;
+static int pty_limit_min;
+static int pty_limit_max = INT_MAX;
+static atomic_t pty_count = ATOMIC_INIT(0);
+
+static struct ctl_table pty_table[] = {
+ {
+ .procname = "max",
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .data = &pty_limit,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &pty_limit_min,
+ .extra2 = &pty_limit_max,
+ }, {
+ .procname = "reserve",
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .data = &pty_reserve,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &pty_limit_min,
+ .extra2 = &pty_limit_max,
+ }, {
+ .procname = "nr",
+ .maxlen = sizeof(int),
+ .mode = 0444,
+ .data = &pty_count,
+ .proc_handler = proc_dointvec,
+ },
+ {}
+};
+
+struct pts_mount_opts {
+ int setuid;
+ int setgid;
+ kuid_t uid;
+ kgid_t gid;
+ umode_t mode;
+ umode_t ptmxmode;
+ int reserve;
+ int max;
+};
+
+enum {
+ Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max,
+ Opt_err
+};
+
+static const match_table_t tokens = {
+ {Opt_uid, "uid=%u"},
+ {Opt_gid, "gid=%u"},
+ {Opt_mode, "mode=%o"},
+ {Opt_ptmxmode, "ptmxmode=%o"},
+ {Opt_newinstance, "newinstance"},
+ {Opt_max, "max=%d"},
+ {Opt_err, NULL}
+};
+
+struct pts_fs_info {
+ struct ida allocated_ptys;
+ struct pts_mount_opts mount_opts;
+ struct super_block *sb;
+ struct dentry *ptmx_dentry;
+};
+
+static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
+{
+ return sb->s_fs_info;
+}
+
+static int devpts_ptmx_path(struct path *path)
+{
+ struct super_block *sb;
+ int err;
+
+ /* Is a devpts filesystem at "pts" in the same directory? */
+ err = path_pts(path);
+ if (err)
+ return err;
+
+ /* Is the path the root of a devpts filesystem? */
+ sb = path->mnt->mnt_sb;
+ if ((sb->s_magic != DEVPTS_SUPER_MAGIC) ||
+ (path->mnt->mnt_root != sb->s_root))
+ return -ENODEV;
+
+ return 0;
+}
+
+/*
+ * Try to find a suitable devpts filesystem. We support the following
+ * scenarios:
+ * - The ptmx device node is located in the same directory as the devpts
+ * mount where the pts device nodes are located.
+ * This is e.g. the case when calling open on the /dev/pts/ptmx device
+ * node when the devpts filesystem is mounted at /dev/pts.
+ * - The ptmx device node is located outside the devpts filesystem mount
+ * where the pts device nodes are located. For example, the ptmx device
+ * is a symlink, separate device node, or bind-mount.
+ * A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and
+ * then calling open on /dev/ptmx. In this case a suitable pts
+ * subdirectory can be found in the common parent directory /dev of the
+ * devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx
+ * bind-mount.
+ * If no suitable pts subdirectory can be found this function will fail.
+ * This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx.
+ */
+struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi)
+{
+ struct path path;
+ int err = 0;
+
+ path = filp->f_path;
+ path_get(&path);
+
+ /* Walk upward while the start point is a bind mount of
+ * a single file.
+ */
+ while (path.mnt->mnt_root == path.dentry)
+ if (follow_up(&path) == 0)
+ break;
+
+ /* devpts_ptmx_path() finds a devpts fs or returns an error. */
+ if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) ||
+ (DEVPTS_SB(path.mnt->mnt_sb) != fsi))
+ err = devpts_ptmx_path(&path);
+ dput(path.dentry);
+ if (!err) {
+ if (DEVPTS_SB(path.mnt->mnt_sb) == fsi)
+ return path.mnt;
+
+ err = -ENODEV;
+ }
+
+ mntput(path.mnt);
+ return ERR_PTR(err);
+}
+
+struct pts_fs_info *devpts_acquire(struct file *filp)
+{
+ struct pts_fs_info *result;
+ struct path path;
+ struct super_block *sb;
+
+ path = filp->f_path;
+ path_get(&path);
+
+ /* Has the devpts filesystem already been found? */
+ if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) {
+ int err;
+
+ err = devpts_ptmx_path(&path);
+ if (err) {
+ result = ERR_PTR(err);
+ goto out;
+ }
+ }
+
+ /*
+ * pty code needs to hold extra references in case of last /dev/tty close
+ */
+ sb = path.mnt->mnt_sb;
+ atomic_inc(&sb->s_active);
+ result = DEVPTS_SB(sb);
+
+out:
+ path_put(&path);
+ return result;
+}
+
+void devpts_release(struct pts_fs_info *fsi)
+{
+ deactivate_super(fsi->sb);
+}
+
+#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.
+ *
+ * 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;
+ kuid_t uid;
+ kgid_t gid;
+
+ opts->setuid = 0;
+ opts->setgid = 0;
+ opts->uid = GLOBAL_ROOT_UID;
+ opts->gid = GLOBAL_ROOT_GID;
+ opts->mode = DEVPTS_DEFAULT_MODE;
+ opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
+ opts->max = NR_UNIX98_PTY_MAX;
+
+ /* Only allow instances mounted from the initial mount
+ * namespace to tap the reserve pool of ptys.
+ */
+ if (op == PARSE_MOUNT)
+ opts->reserve =
+ (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);
+
+ while ((p = strsep(&data, ",")) != NULL) {
+ substring_t args[MAX_OPT_ARGS];
+ int token;
+ int option;
+
+ if (!*p)
+ continue;
+
+ token = match_token(p, tokens, args);
+ switch (token) {
+ case Opt_uid:
+ if (match_int(&args[0], &option))
+ return -EINVAL;
+ uid = make_kuid(current_user_ns(), option);
+ if (!uid_valid(uid))
+ return -EINVAL;
+ opts->uid = uid;
+ opts->setuid = 1;
+ break;
+ case Opt_gid:
+ if (match_int(&args[0], &option))
+ return -EINVAL;
+ gid = make_kgid(current_user_ns(), option);
+ if (!gid_valid(gid))
+ return -EINVAL;
+ opts->gid = gid;
+ opts->setgid = 1;
+ break;
+ case Opt_mode:
+ if (match_octal(&args[0], &option))
+ return -EINVAL;
+ opts->mode = option & S_IALLUGO;
+ break;
+ case Opt_ptmxmode:
+ if (match_octal(&args[0], &option))
+ return -EINVAL;
+ opts->ptmxmode = option & S_IALLUGO;
+ break;
+ case Opt_newinstance:
+ break;
+ case Opt_max:
+ if (match_int(&args[0], &option) ||
+ option < 0 || option > NR_UNIX98_PTY_MAX)
+ return -EINVAL;
+ opts->max = option;
+ break;
+ default:
+ pr_err("called with bogus options\n");
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+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;
+ kuid_t ptmx_uid = current_fsuid();
+ kgid_t ptmx_gid = current_fsgid();
+
+ inode_lock(d_inode(root));
+
+ /* If we have already created ptmx node, return */
+ if (fsi->ptmx_dentry) {
+ rc = 0;
+ goto out;
+ }
+
+ dentry = d_alloc_name(root, "ptmx");
+ if (!dentry) {
+ pr_err("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) {
+ pr_err("Unable to alloc inode for ptmx node\n");
+ dput(dentry);
+ goto out;
+ }
+
+ inode->i_ino = 2;
+ inode->i_mtime = inode->i_atime = inode_set_ctime_current(inode);
+
+ mode = S_IFCHR|opts->ptmxmode;
+ init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+ inode->i_uid = ptmx_uid;
+ inode->i_gid = ptmx_gid;
+
+ d_add(dentry, inode);
+
+ fsi->ptmx_dentry = dentry;
+ rc = 0;
+out:
+ inode_unlock(d_inode(root));
+ return rc;
+}
+
+static void update_ptmx_mode(struct pts_fs_info *fsi)
+{
+ struct inode *inode;
+ if (fsi->ptmx_dentry) {
+ inode = d_inode(fsi->ptmx_dentry);
+ inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
+ }
+}
+
+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 dentry *root)
+{
+ struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
+ struct pts_mount_opts *opts = &fsi->mount_opts;
+
+ if (opts->setuid)
+ seq_printf(seq, ",uid=%u",
+ from_kuid_munged(&init_user_ns, opts->uid));
+ if (opts->setgid)
+ seq_printf(seq, ",gid=%u",
+ from_kgid_munged(&init_user_ns, opts->gid));
+ seq_printf(seq, ",mode=%03o", opts->mode);
+ seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+ if (opts->max < NR_UNIX98_PTY_MAX)
+ seq_printf(seq, ",max=%d", opts->max);
+
+ return 0;
+}
+
+static const struct super_operations devpts_sops = {
+ .statfs = simple_statfs,
+ .remount_fs = devpts_remount,
+ .show_options = devpts_show_options,
+};
+
+static void *new_pts_fs_info(struct super_block *sb)
+{
+ struct pts_fs_info *fsi;
+
+ fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
+ if (!fsi)
+ return NULL;
+
+ ida_init(&fsi->allocated_ptys);
+ fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
+ fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
+ fsi->sb = sb;
+
+ return fsi;
+}
+
+static int
+devpts_fill_super(struct super_block *s, void *data, int silent)
+{
+ struct inode *inode;
+ int error;
+
+ s->s_iflags &= ~SB_I_NODEV;
+ s->s_blocksize = 1024;
+ s->s_blocksize_bits = 10;
+ s->s_magic = DEVPTS_SUPER_MAGIC;
+ s->s_op = &devpts_sops;
+ s->s_d_op = &simple_dentry_operations;
+ s->s_time_gran = 1;
+
+ error = -ENOMEM;
+ s->s_fs_info = new_pts_fs_info(s);
+ if (!s->s_fs_info)
+ goto fail;
+
+ error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts);
+ if (error)
+ goto fail;
+
+ error = -ENOMEM;
+ inode = new_inode(s);
+ if (!inode)
+ goto fail;
+ inode->i_ino = 1;
+ inode->i_mtime = inode->i_atime = inode_set_ctime_current(inode);
+ inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
+ inode->i_op = &simple_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+ set_nlink(inode, 2);
+
+ s->s_root = d_make_root(inode);
+ if (!s->s_root) {
+ pr_err("get root dentry failed\n");
+ goto fail;
+ }
+
+ error = mknod_ptmx(s);
+ if (error)
+ goto fail_dput;
+
+ return 0;
+fail_dput:
+ dput(s->s_root);
+ s->s_root = NULL;
+fail:
+ return error;
+}
+
+/*
+ * devpts_mount()
+ *
+ * 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)
+{
+ return mount_nodev(fs_type, flags, data, devpts_fill_super);
+}
+
+static void devpts_kill_sb(struct super_block *sb)
+{
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+
+ if (fsi)
+ ida_destroy(&fsi->allocated_ptys);
+ kfree(fsi);
+ kill_litter_super(sb);
+}
+
+static struct file_system_type devpts_fs_type = {
+ .name = "devpts",
+ .mount = devpts_mount,
+ .kill_sb = devpts_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+
+/*
+ * The normal naming convention is simply /dev/pts/<number>; this conforms
+ * to the System V naming convention
+ */
+
+int devpts_new_index(struct pts_fs_info *fsi)
+{
+ int index = -ENOSPC;
+
+ if (atomic_inc_return(&pty_count) >= (pty_limit -
+ (fsi->mount_opts.reserve ? 0 : pty_reserve)))
+ goto out;
+
+ index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1,
+ GFP_KERNEL);
+
+out:
+ if (index < 0)
+ atomic_dec(&pty_count);
+ return index;
+}
+
+void devpts_kill_index(struct pts_fs_info *fsi, int idx)
+{
+ ida_free(&fsi->allocated_ptys, idx);
+ atomic_dec(&pty_count);
+}
+
+/**
+ * devpts_pty_new -- create a new inode in /dev/pts/
+ * @fsi: Filesystem info for this instance.
+ * @index: used as a name of the node
+ * @priv: what's given back by devpts_get_priv
+ *
+ * The dentry for the created inode is returned.
+ * Remove it from /dev/pts/ with devpts_pty_kill().
+ */
+struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
+{
+ struct dentry *dentry;
+ struct super_block *sb = fsi->sb;
+ struct inode *inode;
+ struct dentry *root;
+ struct pts_mount_opts *opts;
+ char s[12];
+
+ root = sb->s_root;
+ opts = &fsi->mount_opts;
+
+ inode = new_inode(sb);
+ if (!inode)
+ return ERR_PTR(-ENOMEM);
+
+ inode->i_ino = index + 3;
+ inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
+ inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
+ inode->i_mtime = inode->i_atime = inode_set_ctime_current(inode);
+ init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index));
+
+ sprintf(s, "%d", index);
+
+ dentry = d_alloc_name(root, s);
+ if (dentry) {
+ dentry->d_fsdata = priv;
+ d_add(dentry, inode);
+ fsnotify_create(d_inode(root), dentry);
+ } else {
+ iput(inode);
+ dentry = ERR_PTR(-ENOMEM);
+ }
+
+ return dentry;
+}
+
+/**
+ * devpts_get_priv -- get private data for a slave
+ * @dentry: dentry of the slave
+ *
+ * Returns whatever was passed as priv in devpts_pty_new for a given inode.
+ */
+void *devpts_get_priv(struct dentry *dentry)
+{
+ if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
+ return NULL;
+ return dentry->d_fsdata;
+}
+
+/**
+ * devpts_pty_kill -- remove inode form /dev/pts/
+ * @dentry: dentry of the slave to be removed
+ *
+ * This is an inverse operation of devpts_pty_new.
+ */
+void devpts_pty_kill(struct dentry *dentry)
+{
+ WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);
+
+ dentry->d_fsdata = NULL;
+ drop_nlink(dentry->d_inode);
+ d_drop(dentry);
+ fsnotify_unlink(d_inode(dentry->d_parent), dentry);
+ dput(dentry); /* d_alloc_name() in devpts_pty_new() */
+}
+
+static int __init init_devpts_fs(void)
+{
+ int err = register_filesystem(&devpts_fs_type);
+ if (!err) {
+ register_sysctl("kernel/pty", pty_table);
+ }
+ return err;
+}
+module_init(init_devpts_fs)
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-20 16:54:29 +0000