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path: root/fs/devpts/inode.c
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Diffstat (limited to 'fs/devpts/inode.c')
-rw-r--r--fs/devpts/inode.c246
1 files changed, 181 insertions, 65 deletions
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index 1bb547c9cad..cfe8466f7fe 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -10,6 +10,8 @@
*
* ------------------------------------------------------------------------- */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
@@ -36,7 +38,61 @@
#define DEVPTS_DEFAULT_PTMX_MODE 0000
#define PTMX_MINOR 2
-extern int pty_limit; /* Config limit on Unix98 ptys */
+/*
+ * 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 int pty_count;
+
+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,
+ },
+ {}
+};
+
+static struct ctl_table pty_kern_table[] = {
+ {
+ .procname = "pty",
+ .mode = 0555,
+ .child = pty_table,
+ },
+ {}
+};
+
+static struct ctl_table pty_root_table[] = {
+ {
+ .procname = "kernel",
+ .mode = 0555,
+ .child = pty_kern_table,
+ },
+ {}
+};
+
static DEFINE_MUTEX(allocated_ptys_lock);
static struct vfsmount *devpts_mnt;
@@ -44,15 +100,16 @@ static struct vfsmount *devpts_mnt;
struct pts_mount_opts {
int setuid;
int setgid;
- uid_t uid;
- gid_t gid;
+ kuid_t uid;
+ kgid_t gid;
umode_t mode;
umode_t ptmxmode;
int newinstance;
+ int max;
};
enum {
- Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
+ Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max,
Opt_err
};
@@ -63,6 +120,7 @@ static const match_table_t tokens = {
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
{Opt_ptmxmode, "ptmxmode=%o"},
{Opt_newinstance, "newinstance"},
+ {Opt_max, "max=%d"},
#endif
{Opt_err, NULL}
};
@@ -92,23 +150,26 @@ static inline struct super_block *pts_sb_from_inode(struct inode *inode)
/*
* 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. The exception is
- * 'newinstance' option which can only be set/cleared on a mount (i.e.
- * cannot be changed during remount).
+ * Set @opts to mount options specified in @data. If an option is not
+ * specified in @data, set it to its default value. The exception is
+ * 'newinstance' option which can only be set/cleared on a mount (i.e.
+ * cannot be changed during remount).
*
* 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 = 0;
- opts->gid = 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;
/* newinstance makes sense only on initial mount */
if (op == PARSE_MOUNT)
@@ -127,13 +188,19 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
case Opt_uid:
if (match_int(&args[0], &option))
return -EINVAL;
- opts->uid = option;
+ 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;
- opts->gid = option;
+ gid = make_kgid(current_user_ns(), option);
+ if (!gid_valid(gid))
+ return -EINVAL;
+ opts->gid = gid;
opts->setgid = 1;
break;
case Opt_mode:
@@ -152,9 +219,15 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
if (op == PARSE_MOUNT)
opts->newinstance = 1;
break;
+ case Opt_max:
+ if (match_int(&args[0], &option) ||
+ option < 0 || option > NR_UNIX98_PTY_MAX)
+ return -EINVAL;
+ opts->max = option;
+ break;
#endif
default:
- printk(KERN_ERR "devpts: called with bogus options\n");
+ pr_err("called with bogus options\n");
return -EINVAL;
}
}
@@ -172,6 +245,13 @@ static int mknod_ptmx(struct super_block *sb)
struct dentry *root = sb->s_root;
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
+ kuid_t root_uid;
+ kgid_t root_gid;
+
+ root_uid = make_kuid(current_user_ns(), 0);
+ root_gid = make_kgid(current_user_ns(), 0);
+ if (!uid_valid(root_uid) || !gid_valid(root_gid))
+ return -EINVAL;
mutex_lock(&root->d_inode->i_mutex);
@@ -183,7 +263,7 @@ static int mknod_ptmx(struct super_block *sb)
dentry = d_alloc_name(root, "ptmx");
if (!dentry) {
- printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
+ pr_err("Unable to alloc dentry for ptmx node\n");
goto out;
}
@@ -192,7 +272,7 @@ static int mknod_ptmx(struct super_block *sb)
*/
inode = new_inode(sb);
if (!inode) {
- printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
+ pr_err("Unable to alloc inode for ptmx node\n");
dput(dentry);
goto out;
}
@@ -202,6 +282,8 @@ static int mknod_ptmx(struct super_block *sb)
mode = S_IFCHR|opts->ptmxmode;
init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+ inode->i_uid = root_uid;
+ inode->i_gid = root_gid;
d_add(dentry, inode);
@@ -223,7 +305,7 @@ static void update_ptmx_mode(struct pts_fs_info *fsi)
#else
static inline void update_ptmx_mode(struct pts_fs_info *fsi)
{
- return;
+ return;
}
#endif
@@ -233,6 +315,7 @@ 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;
+ sync_filesystem(sb);
err = parse_mount_options(data, PARSE_REMOUNT, opts);
/*
@@ -246,18 +329,22 @@ static int devpts_remount(struct super_block *sb, int *flags, char *data)
return err;
}
-static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
+static int devpts_show_options(struct seq_file *seq, struct dentry *root)
{
- struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
+ 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", opts->uid);
+ seq_printf(seq, ",uid=%u",
+ from_kuid_munged(&init_user_ns, opts->uid));
if (opts->setgid)
- seq_printf(seq, ",gid=%u", opts->gid);
+ seq_printf(seq, ",gid=%u",
+ from_kgid_munged(&init_user_ns, opts->gid));
seq_printf(seq, ",mode=%03o", opts->mode);
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+ if (opts->max < NR_UNIX98_PTY_MAX)
+ seq_printf(seq, ",max=%d", opts->max);
#endif
return 0;
@@ -301,23 +388,20 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
inode = new_inode(s);
if (!inode)
- goto free_fsi;
+ goto fail;
inode->i_ino = 1;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
- inode->i_nlink = 2;
+ set_nlink(inode, 2);
- s->s_root = d_alloc_root(inode);
+ s->s_root = d_make_root(inode);
if (s->s_root)
return 0;
- printk(KERN_ERR "devpts: get root dentry failed\n");
- iput(inode);
+ pr_err("get root dentry failed\n");
-free_fsi:
- kfree(s->s_fs_info);
fail:
return -ENOMEM;
}
@@ -368,16 +452,22 @@ static struct dentry *devpts_mount(struct file_system_type *fs_type,
if (error)
return ERR_PTR(error);
+ /* Require newinstance for all user namespace mounts to ensure
+ * the mount options are not changed.
+ */
+ if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
+ return ERR_PTR(-EINVAL);
+
if (opts.newinstance)
- s = sget(fs_type, NULL, set_anon_super, NULL);
+ s = sget(fs_type, NULL, set_anon_super, flags, NULL);
else
- s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
+ s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags,
+ NULL);
if (IS_ERR(s))
return ERR_CAST(s);
if (!s->s_root) {
- s->s_flags = flags;
error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error)
goto out_undo_sget;
@@ -413,6 +503,7 @@ static void devpts_kill_sb(struct super_block *sb)
{
struct pts_fs_info *fsi = DEVPTS_SB(sb);
+ ida_destroy(&fsi->allocated_ptys);
kfree(fsi);
kill_litter_super(sb);
}
@@ -421,6 +512,9 @@ static struct file_system_type devpts_fs_type = {
.name = "devpts",
.mount = devpts_mount,
.kill_sb = devpts_kill_sb,
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ .fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
+#endif
};
/*
@@ -440,6 +534,12 @@ retry:
return -ENOMEM;
mutex_lock(&allocated_ptys_lock);
+ if (pty_count >= pty_limit -
+ (fsi->mount_opts.newinstance ? pty_reserve : 0)) {
+ mutex_unlock(&allocated_ptys_lock);
+ return -ENOSPC;
+ }
+
ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
if (ida_ret < 0) {
mutex_unlock(&allocated_ptys_lock);
@@ -448,11 +548,12 @@ retry:
return -EIO;
}
- if (index >= pty_limit) {
+ if (index >= fsi->mount_opts.max) {
ida_remove(&fsi->allocated_ptys, index);
mutex_unlock(&allocated_ptys_lock);
- return -EIO;
+ return -ENOSPC;
}
+ pty_count++;
mutex_unlock(&allocated_ptys_lock);
return index;
}
@@ -464,57 +565,69 @@ void devpts_kill_index(struct inode *ptmx_inode, int idx)
mutex_lock(&allocated_ptys_lock);
ida_remove(&fsi->allocated_ptys, idx);
+ pty_count--;
mutex_unlock(&allocated_ptys_lock);
}
-int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
+/**
+ * devpts_pty_new -- create a new inode in /dev/pts/
+ * @ptmx_inode: inode of the master
+ * @device: major+minor of the node to be created
+ * @index: used as a name of the node
+ * @priv: what's given back by devpts_get_priv
+ *
+ * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill.
+ */
+struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index,
+ void *priv)
{
- /* 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 super_block *sb = pts_sb_from_inode(ptmx_inode);
- struct inode *inode = new_inode(sb);
+ 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;
char s[12];
- /* We're supposed to be given the slave end of a pty */
- BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
- BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
-
+ inode = new_inode(sb);
if (!inode)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
- inode->i_ino = number + 3;
+ 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->i_ctime = CURRENT_TIME;
init_special_inode(inode, S_IFCHR|opts->mode, device);
- inode->i_private = tty;
- tty->driver_data = inode;
+ inode->i_private = priv;
- sprintf(s, "%d", number);
+ sprintf(s, "%d", index);
mutex_lock(&root->d_inode->i_mutex);
dentry = d_alloc_name(root, s);
- if (!IS_ERR(dentry)) {
+ if (dentry) {
d_add(dentry, inode);
fsnotify_create(root->d_inode, dentry);
+ } else {
+ iput(inode);
+ inode = ERR_PTR(-ENOMEM);
}
mutex_unlock(&root->d_inode->i_mutex);
- return 0;
+ return inode;
}
-struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
+/**
+ * devpts_get_priv -- get private data for a slave
+ * @pts_inode: inode of the slave
+ *
+ * Returns whatever was passed as priv in devpts_pty_new for a given inode.
+ */
+void *devpts_get_priv(struct inode *pts_inode)
{
struct dentry *dentry;
- struct tty_struct *tty;
+ void *priv = NULL;
BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
@@ -523,18 +636,22 @@ struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
if (!dentry)
return NULL;
- tty = NULL;
if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
- tty = (struct tty_struct *)pts_inode->i_private;
+ priv = pts_inode->i_private;
dput(dentry);
- return tty;
+ return priv;
}
-void devpts_pty_kill(struct tty_struct *tty)
+/**
+ * devpts_pty_kill -- remove inode form /dev/pts/
+ * @inode: inode of the slave to be removed
+ *
+ * This is an inverse operation of devpts_pty_new.
+ */
+void devpts_pty_kill(struct inode *inode)
{
- struct inode *inode = tty->driver_data;
struct super_block *sb = pts_sb_from_inode(inode);
struct dentry *root = sb->s_root;
struct dentry *dentry;
@@ -544,28 +661,27 @@ void devpts_pty_kill(struct tty_struct *tty)
mutex_lock(&root->d_inode->i_mutex);
dentry = d_find_alias(inode);
- if (IS_ERR(dentry))
- goto out;
-
- if (dentry) {
- inode->i_nlink--;
- d_delete(dentry);
- dput(dentry); /* d_alloc_name() in devpts_pty_new() */
- }
+ drop_nlink(inode);
+ d_delete(dentry);
+ dput(dentry); /* d_alloc_name() in devpts_pty_new() */
dput(dentry); /* d_find_alias above */
-out:
+
mutex_unlock(&root->d_inode->i_mutex);
}
static int __init init_devpts_fs(void)
{
int err = register_filesystem(&devpts_fs_type);
+ struct ctl_table_header *table;
+
if (!err) {
+ table = register_sysctl_table(pty_root_table);
devpts_mnt = kern_mount(&devpts_fs_type);
if (IS_ERR(devpts_mnt)) {
err = PTR_ERR(devpts_mnt);
unregister_filesystem(&devpts_fs_type);
+ unregister_sysctl_table(table);
}
}
return err;
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-04 13:08:11 +0000