diff options
Diffstat (limited to 'fs')
-rw-r--r-- | fs/devpts/inode.c | 472 |
1 files changed, 426 insertions, 46 deletions
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c index 5d61b7c06e13..fff96e152c0c 100644 --- a/fs/devpts/inode.c +++ b/fs/devpts/inode.c @@ -27,25 +27,32 @@ #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 DEFINE_IDA(allocated_ptys); static DEFINE_MUTEX(allocated_ptys_lock); static struct vfsmount *devpts_mnt; -static struct dentry *devpts_root; -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 }; @@ -53,18 +60,50 @@ static const match_table_t tokens = { {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} }; -static int devpts_remount(struct super_block *sb, int *flags, char *data) +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) +{ + return sb->s_fs_info; +} + +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; +} + +#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]; @@ -79,20 +118,32 @@ static int devpts_remount(struct super_block *sb, int *flags, char *data) 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; @@ -102,13 +153,108 @@ static int devpts_remount(struct super_block *sb, int *flags, char *data) 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; } @@ -119,10 +265,25 @@ static const struct super_operations devpts_sops = { .show_options = devpts_show_options, }; +static void *new_pts_fs_info(void) +{ + 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; + + 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; @@ -130,9 +291,13 @@ devpts_fill_super(struct super_block *s, void *data, int silent) s->s_op = &devpts_sops; s->s_time_gran = 1; + s->s_fs_info = new_pts_fs_info(); + if (!s->s_fs_info) + goto fail; + inode = new_inode(s); if (!inode) - goto fail; + goto free_fsi; inode->i_ino = 1; inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; inode->i_blocks = 0; @@ -142,27 +307,226 @@ devpts_fill_super(struct super_block *s, void *data, int silent) inode->i_fop = &simple_dir_operations; inode->i_nlink = 2; - devpts_root = s->s_root = d_alloc_root(inode); + s->s_root = d_alloc_root(inode); if (s->s_root) return 0; - - printk("devpts: get root dentry failed\n"); + + printk(KERN_ERR "devpts: get root dentry failed\n"); iput(inode); + +free_fsi: + kfree(s->s_fs_info); fail: return -ENOMEM; } +#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; +} + +/* + * 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_litter_super(sb); +} static struct file_system_type devpts_fs_type = { .owner = THIS_MODULE, .name = "devpts", .get_sb = devpts_get_sb, - .kill_sb = kill_anon_super, + .kill_sb = devpts_kill_sb, }; /* @@ -172,16 +536,17 @@ static struct file_system_type devpts_fs_type = { int devpts_new_index(struct inode *ptmx_inode) { + struct super_block *sb = pts_sb_from_inode(ptmx_inode); + struct pts_fs_info *fsi = DEVPTS_SB(sb); int index; int ida_ret; retry: - if (!ida_pre_get(&allocated_ptys, GFP_KERNEL)) { + if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) return -ENOMEM; - } mutex_lock(&allocated_ptys_lock); - ida_ret = ida_get_new(&allocated_ptys, &index); + ida_ret = ida_get_new(&fsi->allocated_ptys, &index); if (ida_ret < 0) { mutex_unlock(&allocated_ptys_lock); if (ida_ret == -EAGAIN) @@ -190,7 +555,7 @@ retry: } if (index >= pty_limit) { - ida_remove(&allocated_ptys, index); + ida_remove(&fsi->allocated_ptys, index); mutex_unlock(&allocated_ptys_lock); return -EIO; } @@ -200,18 +565,26 @@ retry: void devpts_kill_index(struct inode *ptmx_inode, int idx) { + struct super_block *sb = pts_sb_from_inode(ptmx_inode); + struct pts_fs_info *fsi = DEVPTS_SB(sb); + mutex_lock(&allocated_ptys_lock); - ida_remove(&allocated_ptys, idx); + ida_remove(&fsi->allocated_ptys, idx); mutex_unlock(&allocated_ptys_lock); } int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty) { - int number = tty->index; /* tty layer puts index from devpts_new_index() in here */ + /* tty layer puts index from devpts_new_index() in here */ + int number = tty->index; struct tty_driver *driver = tty->driver; dev_t device = MKDEV(driver->major, driver->minor_start+number); struct dentry *dentry; - struct inode *inode = new_inode(devpts_mnt->mnt_sb); + 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 */ @@ -221,25 +594,25 @@ int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty) if (!inode) return -ENOMEM; - inode->i_ino = number+2; - inode->i_uid = config.setuid ? config.uid : current_fsuid(); - inode->i_gid = config.setgid ? config.gid : current_fsgid(); + inode->i_ino = number + 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->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; sprintf(s, "%d", number); - mutex_lock(&devpts_root->d_inode->i_mutex); + mutex_lock(&root->d_inode->i_mutex); - dentry = d_alloc_name(devpts_root, s); + dentry = d_alloc_name(root, s); if (!IS_ERR(dentry)) { d_add(dentry, inode); - fsnotify_create(devpts_root->d_inode, dentry); + fsnotify_create(root->d_inode, dentry); } - mutex_unlock(&devpts_root->d_inode->i_mutex); + mutex_unlock(&root->d_inode->i_mutex); return 0; } @@ -256,20 +629,27 @@ struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number) void devpts_pty_kill(struct tty_struct *tty) { struct inode *inode = tty->driver_data; + struct super_block *sb = pts_sb_from_inode(inode); + struct dentry *root = sb->s_root; struct dentry *dentry; BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); - mutex_lock(&devpts_root->d_inode->i_mutex); + 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() */ } - mutex_unlock(&devpts_root->d_inode->i_mutex); + dput(dentry); /* d_find_alias above */ +out: + mutex_unlock(&root->d_inode->i_mutex); } static int __init init_devpts_fs(void) |