[Devel] [RFC PATCH 2/2] ipc namespaces: implement support for posix msqueues
Serge E. Hallyn
serue at us.ibm.com
Mon Dec 15 15:38:23 PST 2008
Implement multiple mounts of the mqueue file system, and
link it to usage of CLONE_NEWIPC.
Each ipc ns has a corresponding mqueuefs superblock. When
a user does clone(CLONE_NEWIPC) or unshare(CLONE_NEWIPC), the
unshare will cause an internal mount of a new mqueuefs sb
linked to the new ipc ns.
When a user does 'mount -t mqueue mqueue /dev/mqueue', he
mounts the mqueuefs superblock.
Posix message queues can be worked with both through the
mq_* system calls (see mq_overview(7)), and through the VFS
through the mqueue mount. Any usage of mq_open() and friends
will work with the acting task's ipc namespace. Any actions
through the VFS will work with the mqueuefs in which the
file was created. So if a user doesn't remount mqueuefs
after unshare(CLONE_NEWIPC), mq_open("/ab") will not be
reflected in "ls /dev/mqueue".
If task a mounts mqueue for ipc_ns:1, then clones task b with
a new ipcns, ipcns:2, and then task a is the last task in
ipc_ns:1 to exit, then (1) ipc_ns:1 will be freed, (2) it's
superblock will live on until task b umounts the corresponding
mqueuefs, and vfs actions will continue to succeed, but (3)
sb->s_fs_info will be NULL for the sb corresponding to the
deceased ipc_ns:1.
Largely based on previous version by Cedric Le Goater <clg at fr.ibm.com>
and Nadia Derbey <Nadia.Derbey at bull.net>.
Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
---
include/linux/ipc_namespace.h | 16 ++---
ipc/mqueue.c | 150 +++++++++++++++++++++++++++++++++--------
ipc/msgutil.c | 8 +--
ipc/namespace.c | 25 +++++--
ipc/util.h | 6 +-
5 files changed, 154 insertions(+), 51 deletions(-)
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 532598f..74f1ae2 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -25,7 +25,7 @@ struct ipc_ids {
};
struct ipc_namespace {
- struct kref kref;
+ atomic_t count;
struct ipc_ids ids[3];
int sem_ctls[4];
@@ -56,6 +56,7 @@ struct ipc_namespace {
extern struct ipc_namespace init_ipc_ns;
extern atomic_t nr_ipc_ns;
+extern spinlock_t mq_lock;
#if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC)
#define INIT_IPC_NS(ns) .ns = &init_ipc_ns,
#else
@@ -75,18 +76,18 @@ extern int ipcns_notify(unsigned long);
#endif /* CONFIG_SYSVIPC */
#ifdef CONFIG_POSIX_MQUEUE
-extern void mq_init_ns(struct ipc_namespace *ns);
+extern int mq_init_ns(struct ipc_namespace *ns);
/* default values */
#define DFLT_QUEUESMAX 256 /* max number of message queues */
#define DFLT_MSGMAX 10 /* max number of messages in each queue */
#define HARD_MSGMAX (131072/sizeof(void *))
#define DFLT_MSGSIZEMAX 8192 /* max message size */
#else
-#define mq_init_ns(ns)
+#define mq_init_ns(ns) (0)
#endif
#if defined(CONFIG_IPC_NS)
-extern void free_ipc_ns(struct kref *kref);
+extern void free_ipc_ns(struct ipc_namespace *ns);
extern struct ipc_namespace *copy_ipcs(unsigned long flags,
struct ipc_namespace *ns);
extern void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
@@ -96,14 +97,11 @@ extern void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
{
if (ns)
- kref_get(&ns->kref);
+ atomic_inc(&ns->count);
return ns;
}
-static inline void put_ipc_ns(struct ipc_namespace *ns)
-{
- kref_put(&ns->kref, free_ipc_ns);
-}
+extern void put_ipc_ns(struct ipc_namespace *ns);
#else
static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
struct ipc_namespace *ns)
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 01d64a0..de31ef7 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -88,7 +88,6 @@ static const struct file_operations mqueue_file_operations;
static struct super_operations mqueue_super_ops;
static void remove_notification(struct mqueue_inode_info *info);
-static spinlock_t mq_lock;
static struct kmem_cache *mqueue_inode_cachep;
static struct ctl_table_header * mq_sysctl_table;
@@ -98,25 +97,40 @@ static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode)
return container_of(inode, struct mqueue_inode_info, vfs_inode);
}
-void mq_init_ns(struct ipc_namespace *ns) {
- ns->mq_queues_count = 0;
- ns->mq_queues_max = DFLT_QUEUESMAX;
- ns->mq_msg_max = DFLT_MSGMAX;
- ns->mq_msgsize_max = DFLT_MSGSIZEMAX;
- ns->mq_mnt = mntget(init_ipc_ns.mq_mnt);
+/*
+ * This routine should be called with the mq_lock held.
+ */
+static inline struct ipc_namespace *__get_ns_from_ino(struct inode *inode)
+{
+ return get_ipc_ns(inode->i_sb->s_fs_info);
}
-void mq_exit_ns(struct ipc_namespace *ns) {
- /* will need to clear out ns->mq_mnt->mnt_sb->s_fs_info here */
- mntput(ns->mq_mnt);
+static inline struct ipc_namespace *get_ns_from_ino(struct inode *inode)
+{
+ struct ipc_namespace *ns;
+
+ spin_lock(&mq_lock);
+ ns = __get_ns_from_ino(inode);
+ spin_unlock(&mq_lock);
+ return ns;
+}
+
+static inline struct ipc_namespace *get_ns_from_sb(struct super_block *sb)
+{
+ struct ipc_namespace *ns;
+
+ spin_lock(&mq_lock);
+ ns = get_ipc_ns(sb->s_fs_info);
+ spin_unlock(&mq_lock);
+ return ns;
}
-static struct inode *mqueue_get_inode(struct super_block *sb, int mode,
- struct mq_attr *attr)
+static struct inode *mqueue_get_inode(struct super_block *sb,
+ struct ipc_namespace *ipc_ns, int mode,
+ struct mq_attr *attr)
{
struct user_struct *u = current_user();
struct inode *inode;
- struct ipc_namespace *ipc_ns = &init_ipc_ns;
inode = new_inode(sb);
if (inode) {
@@ -192,30 +206,76 @@ out_inode:
static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
+ struct ipc_namespace *ns = data;
+ int error = 0;
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = MQUEUE_MAGIC;
sb->s_op = &mqueue_super_ops;
- inode = mqueue_get_inode(sb, S_IFDIR | S_ISVTX | S_IRWXUGO, NULL);
- if (!inode)
- return -ENOMEM;
+ inode = mqueue_get_inode(sb, ns, S_IFDIR | S_ISVTX | S_IRWXUGO,
+ NULL);
+ if (!inode) {
+ error = -ENOMEM;
+ goto out;
+ }
sb->s_root = d_alloc_root(inode);
if (!sb->s_root) {
iput(inode);
- return -ENOMEM;
+ error = -ENOMEM;
}
- return 0;
+out:
+ return error;
+}
+
+static int compare_sb_single_ns(struct super_block *sb, void *data)
+{
+ return sb->s_fs_info == data;
+}
+
+static int set_sb_single_ns(struct super_block *sb, void *data)
+{
+ sb->s_fs_info = data;
+ return set_anon_super(sb, NULL);
+}
+
+static int get_sb_single_ns(struct file_system_type *fs_type,
+ int flags, void *data,
+ int (*fill_super)(struct super_block *, void *, int),
+ struct vfsmount *mnt)
+{
+ struct super_block *s;
+ int error;
+
+ s = sget(fs_type, compare_sb_single_ns, set_sb_single_ns, data);
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+ if (!s->s_root) {
+ s->s_flags = flags;
+ error = 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);
}
static int mqueue_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, mqueue_fill_super, mnt);
+ if (flags & MS_KERNMOUNT)
+ return get_sb_single_ns(fs_type, flags, data,
+ mqueue_fill_super, mnt);
+ return get_sb_single_ns(fs_type, flags, current->nsproxy->ipc_ns,
+ mqueue_fill_super, mnt);
}
static void init_once(void *foo)
@@ -246,12 +306,13 @@ static void mqueue_delete_inode(struct inode *inode)
struct user_struct *user;
unsigned long mq_bytes;
int i;
- struct ipc_namespace *ipc_ns = &init_ipc_ns;
+ struct ipc_namespace *ipc_ns;
if (S_ISDIR(inode->i_mode)) {
clear_inode(inode);
return;
}
+ ipc_ns = get_ns_from_ino(inode);
info = MQUEUE_I(inode);
spin_lock(&info->lock);
for (i = 0; i < info->attr.mq_curmsgs; i++)
@@ -267,10 +328,12 @@ static void mqueue_delete_inode(struct inode *inode)
if (user) {
spin_lock(&mq_lock);
user->mq_bytes -= mq_bytes;
- ipc_ns->mq_queues_count--;
+ if (ipc_ns)
+ ipc_ns->mq_queues_count--;
spin_unlock(&mq_lock);
free_uid(user);
}
+ put_ipc_ns(ipc_ns);
}
static int mqueue_create(struct inode *dir, struct dentry *dentry,
@@ -279,9 +342,14 @@ static int mqueue_create(struct inode *dir, struct dentry *dentry,
struct inode *inode;
struct mq_attr *attr = dentry->d_fsdata;
int error;
- struct ipc_namespace *ipc_ns = &init_ipc_ns;
+ struct ipc_namespace *ipc_ns;
spin_lock(&mq_lock);
+ ipc_ns = __get_ns_from_ino(dir);
+ if (!ipc_ns) {
+ error = -EACCES;
+ goto out_lock;
+ }
if (ipc_ns->mq_queues_count >= ipc_ns->mq_queues_max &&
!capable(CAP_SYS_RESOURCE)) {
error = -ENOSPC;
@@ -290,7 +358,7 @@ static int mqueue_create(struct inode *dir, struct dentry *dentry,
ipc_ns->mq_queues_count++;
spin_unlock(&mq_lock);
- inode = mqueue_get_inode(dir->i_sb, mode, attr);
+ inode = mqueue_get_inode(dir->i_sb, ipc_ns, mode, attr);
if (!inode) {
error = -ENOMEM;
spin_lock(&mq_lock);
@@ -298,6 +366,7 @@ static int mqueue_create(struct inode *dir, struct dentry *dentry,
goto out_lock;
}
+ put_ipc_ns(ipc_ns);
dir->i_size += DIRENT_SIZE;
dir->i_ctime = dir->i_mtime = dir->i_atime = CURRENT_TIME;
@@ -306,6 +375,7 @@ static int mqueue_create(struct inode *dir, struct dentry *dentry,
return 0;
out_lock:
spin_unlock(&mq_lock);
+ put_ipc_ns(ipc_ns);
return error;
}
@@ -673,7 +743,7 @@ asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,
struct file *filp;
char *name;
int fd, error;
- struct ipc_namespace *ipc_ns = &init_ipc_ns;
+ struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
error = audit_mq_open(oflag, mode, u_attr);
if (error != 0)
@@ -741,7 +811,7 @@ asmlinkage long sys_mq_unlink(const char __user *u_name)
char *name;
struct dentry *dentry;
struct inode *inode = NULL;
- struct ipc_namespace *ipc_ns = &init_ipc_ns;
+ struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
name = getname(u_name);
if (IS_ERR(name))
@@ -1212,6 +1282,29 @@ static struct file_system_type mqueue_fs_type = {
.kill_sb = kill_litter_super,
};
+int mq_init_ns(struct ipc_namespace *ns)
+{
+ ns->mq_queues_count = 0;
+ ns->mq_queues_max = DFLT_QUEUESMAX;
+ ns->mq_msg_max = DFLT_MSGMAX;
+ ns->mq_msgsize_max = DFLT_MSGSIZEMAX;
+
+ ns->mq_mnt = kern_mount_data(&mqueue_fs_type, ns);
+ if (IS_ERR(ns->mq_mnt))
+ return PTR_ERR(ns->mq_mnt);
+ return 0;
+}
+
+void mq_clear_sbinfo(struct ipc_namespace *ns)
+{
+ ns->mq_mnt->mnt_sb->s_fs_info = NULL;
+}
+
+void mq_put_mnt(struct ipc_namespace *ns)
+{
+ mntput(ns->mq_mnt);
+}
+
static int msg_max_limit_min = MIN_MSGMAX;
static int msg_max_limit_max = MAX_MSGMAX;
@@ -1283,15 +1376,14 @@ static int __init init_mqueue_fs(void)
if (error)
goto out_sysctl;
- init_ipc_ns.mq_mnt = kern_mount(&mqueue_fs_type);
+ spin_lock_init(&mq_lock);
+
+ init_ipc_ns.mq_mnt = kern_mount_data(&mqueue_fs_type, &init_ipc_ns);
if (IS_ERR(init_ipc_ns.mq_mnt)) {
error = PTR_ERR(init_ipc_ns.mq_mnt);
goto out_filesystem;
}
- /* internal initialization - not common for vfs */
- spin_lock_init(&mq_lock);
-
return 0;
out_filesystem:
diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index c197cd1..21475b0 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -18,18 +18,16 @@
#include "util.h"
+spinlock_t mq_lock;
+
/*
* The next 2 defines are here bc this is the only file
* compiled when either CONFIG_SYSVIPC and CONFIG_POSIX_MQUEUE
* and not CONFIG_IPC_NS.
*/
struct ipc_namespace init_ipc_ns = {
- .kref = {
- .refcount = ATOMIC_INIT(2),
- },
+ .count = ATOMIC_INIT(2),
#ifdef CONFIG_POSIX_MQUEUE
- .mq_mnt = NULL,
- .mq_queues_count = 0,
.mq_queues_max = DFLT_QUEUESMAX,
.mq_msg_max = DFLT_MSGMAX,
.mq_msgsize_max = DFLT_MSGSIZEMAX,
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 4b4dc6d..a4f36ba 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -9,23 +9,31 @@
#include <linux/rcupdate.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
#include "util.h"
static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
{
struct ipc_namespace *ns;
+ int err;
ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
if (ns == NULL)
return ERR_PTR(-ENOMEM);
+ atomic_set(&ns->count, 1);
+ err = mq_init_ns(ns);
+ if (err) {
+ kfree(ns);
+ return ERR_PTR(err);
+ }
atomic_inc(&nr_ipc_ns);
sem_init_ns(ns);
msg_init_ns(ns);
shm_init_ns(ns);
- mq_init_ns(ns);
/*
* msgmni has already been computed for the new ipc ns.
@@ -35,7 +43,6 @@ static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
ipcns_notify(IPCNS_CREATED);
register_ipcns_notifier(ns);
- kref_init(&ns->kref);
return ns;
}
@@ -85,11 +92,18 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
up_write(&ids->rw_mutex);
}
-void free_ipc_ns(struct kref *kref)
+void put_ipc_ns(struct ipc_namespace *ns)
{
- struct ipc_namespace *ns;
+ if (ns && atomic_dec_and_lock(&ns->count, &mq_lock)) {
+ mq_clear_sbinfo(ns);
+ spin_unlock(&mq_lock);
+ mq_put_mnt(ns);
+ free_ipc_ns(ns);
+ }
+}
- ns = container_of(kref, struct ipc_namespace, kref);
+void free_ipc_ns(struct ipc_namespace *ns)
+{
/*
* Unregistering the hotplug notifier at the beginning guarantees
* that the ipc namespace won't be freed while we are inside the
@@ -102,7 +116,6 @@ void free_ipc_ns(struct kref *kref)
sem_exit_ns(ns);
msg_exit_ns(ns);
shm_exit_ns(ns);
- mq_exit_ns(ns);
kfree(ns);
atomic_dec(&nr_ipc_ns);
diff --git a/ipc/util.h b/ipc/util.h
index 52755c1..b4d213f 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -21,9 +21,11 @@ void shm_init (void);
struct ipc_namespace;
#ifdef CONFIG_POSIX_MQUEUE
-void mq_exit_ns(struct ipc_namespace *ns);
+extern void mq_clear_sbinfo(struct ipc_namespace *ns);
+extern void mq_put_mnt(struct ipc_namespace *ns);
#else
-#define mq_exit_ns(ns)
+#define mq_clear_sbinfo(ns)
+#define mq_put_mnt(ns)
#endif
#ifdef CONFIG_SYSVIPC
--
1.5.4.3
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