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-rw-r--r--fs/devpts/inode.c115
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 = {