diff options
| -rw-r--r-- | fs/devpts/inode.c | 115 |
1 files changed, 110 insertions, 5 deletions
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c index 00530e82673e..8ee9dc2f9e48 100644 --- a/fs/devpts/inode.c +++ b/fs/devpts/inode.c @@ -27,6 +27,13 @@ #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 */ @@ -40,10 +47,11 @@ struct pts_mount_opts { uid_t uid; gid_t gid; umode_t mode; + umode_t ptmxmode; }; enum { - Opt_uid, Opt_gid, Opt_mode, + Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_err }; @@ -51,12 +59,16 @@ 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"}, +#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) @@ -81,6 +93,7 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts) opts->uid = 0; opts->gid = 0; opts->mode = DEVPTS_DEFAULT_MODE; + opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; while ((p = strsep(&data, ",")) != NULL) { substring_t args[MAX_OPT_ARGS]; @@ -109,6 +122,13 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts) return -EINVAL; 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; +#endif default: printk(KERN_ERR "devpts: called with bogus options\n"); return -EINVAL; @@ -118,12 +138,93 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts) 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; - return parse_mount_options(data, opts); + err = parse_mount_options(data, 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) @@ -136,6 +237,9 @@ static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs) 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; } @@ -156,6 +260,7 @@ static void *new_pts_fs_info(void) ida_init(&fsi->allocated_ptys); fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; + fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; return fsi; } @@ -163,7 +268,7 @@ static void *new_pts_fs_info(void) 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; @@ -190,7 +295,7 @@ devpts_fill_super(struct super_block *s, void *data, int silent) s->s_root = d_alloc_root(inode); if (s->s_root) return 0; - + printk("devpts: get root dentry failed\n"); iput(inode); @@ -211,7 +316,7 @@ 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 = { |