diff options
| -rw-r--r-- | fs/devpts/inode.c | 170 |
1 files changed, 163 insertions, 7 deletions
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c index 2d0eb2cf99e6..b4a89fa21673 100644 --- a/fs/devpts/inode.c +++ b/fs/devpts/inode.c @@ -48,10 +48,11 @@ struct pts_mount_opts { gid_t gid; umode_t mode; umode_t ptmxmode; + int newinstance; }; enum { - Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, + Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_err }; @@ -61,6 +62,7 @@ static const match_table_t tokens = { {Opt_mode, "mode=%o"}, #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES {Opt_ptmxmode, "ptmxmode=%o"}, + {Opt_newinstance, "newinstance"}, #endif {Opt_err, NULL} }; @@ -78,13 +80,17 @@ 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 parse_mount_options(char *data, struct pts_mount_opts *opts) +#define PARSE_MOUNT 0 +#define PARSE_REMOUNT 1 + +static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts) { char *p; @@ -95,6 +101,10 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts) 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]; int token; @@ -128,6 +138,11 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts) 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"); @@ -214,7 +229,7 @@ static int devpts_remount(struct super_block *sb, int *flags, char *data) struct pts_fs_info *fsi = DEVPTS_SB(sb); struct pts_mount_opts *opts = &fsi->mount_opts; - err = parse_mount_options(data, opts); + err = parse_mount_options(data, PARSE_REMOUNT, opts); /* * parse_mount_options() restores options to default values @@ -309,8 +324,100 @@ 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; } /* @@ -358,11 +465,54 @@ static int get_init_pts_sb(struct file_system_type *fs_type, int flags, 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) { - return get_init_pts_sb(fs_type, flags, data, 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) { @@ -488,12 +638,18 @@ void devpts_pty_kill(struct tty_struct *tty) 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); } |