#include <linux/proc_fs.h>
#include <linux/audit.h>
#include <linux/nsproxy.h>
+#include <linux/rwsem.h>
#include <asm/unistd.h>
void ipc_init_ids(struct ipc_ids *ids)
{
- mutex_init(&ids->mutex);
+ init_rwsem(&ids->rw_mutex);
ids->in_use = 0;
ids->seq = 0;
* @ids: Identifier set
* @key: The key to find
*
- * Requires ipc_ids.mutex locked.
+ * Requires ipc_ids.rw_mutex locked.
* Returns the LOCKED pointer to the ipc structure if found or NULL
* if not.
- * If key is found ipc contains its ipc structure
+ * If key is found ipc points to the owning ipc structure
*/
static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
* ipc_get_maxid - get the last assigned id
* @ids: IPC identifier set
*
- * Called with ipc_ids.mutex held.
+ * Called with ipc_ids.rw_mutex held.
*/
int ipc_get_maxid(struct ipc_ids *ids)
* @new: new IPC permission set
* @size: limit for the number of used ids
*
- * Add an entry 'new' to the IPC idr. The permissions object is
+ * Add an entry 'new' to the IPC ids idr. The permissions object is
* initialised and the first free entry is set up and the id assigned
- * is returned. The list is returned in a locked state on success.
- * On failure the list is not locked and -1 is returned.
+ * is returned. The 'new' entry is returned in a locked state on success.
+ * On failure the entry is not locked and a negative err-code is returned.
*
- * Called with ipc_ids.mutex held.
+ * Called with ipc_ids.rw_mutex held as a writer.
*/
int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
{
int id, err;
- /*
- * rcu_dereference()() is not needed here since
- * ipc_ids.mutex is held
- */
if (size > IPCMNI)
size = IPCMNI;
if (ids->in_use >= size)
- return -1;
+ return -ENOSPC;
err = idr_get_new(&ids->ipcs_idr, new, &id);
if (err)
- return -1;
+ return err;
ids->in_use++;
/**
* ipcget_new - create a new ipc object
* @ns: namespace
- * @ids: identifer set
+ * @ids: IPC identifer set
* @ops: the actual creation routine to call
* @params: its parameters
*
- * This routine is called sys_msgget, sys_semget() and sys_shmget() when
- * the key is IPC_PRIVATE
+ * This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ * when the key is IPC_PRIVATE.
*/
int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params)
{
int err;
-
+retry:
err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
if (!err)
return -ENOMEM;
- mutex_lock(&ids->mutex);
+ down_write(&ids->rw_mutex);
err = ops->getnew(ns, params);
- mutex_unlock(&ids->mutex);
+ up_write(&ids->rw_mutex);
+
+ if (err == -EAGAIN)
+ goto retry;
return err;
}
/**
* ipc_check_perms - check security and permissions for an IPC
* @ipcp: ipc permission set
- * @ids: identifer set
* @ops: the actual security routine to call
* @params: its parameters
+ *
+ * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
+ * when the key is not IPC_PRIVATE and that key already exists in the
+ * ids IDR.
+ *
+ * On success, the IPC id is returned.
+ *
+ * It is called with ipc_ids.rw_mutex and ipcp->lock held.
*/
static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops,
struct ipc_params *params)
/**
* ipcget_public - get an ipc object or create a new one
* @ns: namespace
- * @ids: identifer set
+ * @ids: IPC identifer set
* @ops: the actual creation routine to call
* @params: its parameters
*
- * This routine is called sys_msgget, sys_semget() and sys_shmget() when
- * the key is not IPC_PRIVATE
+ * This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ * when the key is not IPC_PRIVATE.
+ * It adds a new entry if the key is not found and does some permission
+ * / security checkings if the key is found.
+ *
+ * On success, the ipc id is returned.
*/
int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params)
struct kern_ipc_perm *ipcp;
int flg = params->flg;
int err;
-
+retry:
err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
- mutex_lock(&ids->mutex);
+ /*
+ * Take the lock as a writer since we are potentially going to add
+ * a new entry + read locks are not "upgradable"
+ */
+ down_write(&ids->rw_mutex);
ipcp = ipc_findkey(ids, params->key);
if (ipcp == NULL) {
/* key not used */
if (ops->more_checks)
err = ops->more_checks(ipcp, params);
if (!err)
+ /*
+ * ipc_check_perms returns the IPC id on
+ * success
+ */
err = ipc_check_perms(ipcp, ops, params);
}
ipc_unlock(ipcp);
}
- mutex_unlock(&ids->mutex);
+ up_write(&ids->rw_mutex);
+
+ if (err == -EAGAIN)
+ goto retry;
return err;
}
/**
* ipc_rmid - remove an IPC identifier
- * @ids: identifier set
- * @id: ipc perm structure containing the identifier to remove
+ * @ids: IPC identifier set
+ * @ipcp: ipc perm structure containing the identifier to remove
*
- * The identifier must be valid, and in use. The kernel will panic if
- * fed an invalid identifier. The entry is removed and internal
- * variables recomputed.
- * ipc_ids.mutex and the spinlock for this ID are held before this
- * function is called, and remain locked on the exit.
+ * ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
+ * before this function is called, and remain locked on the exit.
*/
void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
*/
static void ipc_schedule_free(struct rcu_head *head)
{
- struct ipc_rcu_grace *grace =
- container_of(head, struct ipc_rcu_grace, rcu);
- struct ipc_rcu_sched *sched =
- container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
+ struct ipc_rcu_grace *grace;
+ struct ipc_rcu_sched *sched;
+
+ grace = container_of(head, struct ipc_rcu_grace, rcu);
+ sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
+ data[0]);
INIT_WORK(&sched->work, ipc_do_vfree);
schedule_work(&sched->work);
}
/**
- * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
+ * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
* @in: new style IPC permissions
* @out: old style IPC permissions
*
out->seq = in->seq;
}
+/**
+ * ipc_lock - Lock an ipc structure without rw_mutex held
+ * @ids: IPC identifier set
+ * @id: ipc id to look for
+ *
+ * Look for an id in the ipc ids idr and lock the associated ipc object.
+ *
+ * The ipc object is locked on exit.
+ *
+ * This is the routine that should be called when the rw_mutex is not already
+ * held, i.e. idr tree not protected: it protects the idr tree in read mode
+ * during the idr_find().
+ */
+
struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
{
struct kern_ipc_perm *out;
int lid = ipcid_to_idx(id);
+ down_read(&ids->rw_mutex);
+
rcu_read_lock();
out = idr_find(&ids->ipcs_idr, lid);
if (out == NULL) {
rcu_read_unlock();
+ up_read(&ids->rw_mutex);
return ERR_PTR(-EINVAL);
}
+ up_read(&ids->rw_mutex);
+
spin_lock(&out->lock);
/* ipc_rmid() may have already freed the ID while ipc_lock
return out;
}
+/**
+ * ipc_lock_down - Lock an ipc structure with rw_sem held
+ * @ids: IPC identifier set
+ * @id: ipc id to look for
+ *
+ * Look for an id in the ipc ids idr and lock the associated ipc object.
+ *
+ * The ipc object is locked on exit.
+ *
+ * This is the routine that should be called when the rw_mutex is already
+ * held, i.e. idr tree protected.
+ */
+
+struct kern_ipc_perm *ipc_lock_down(struct ipc_ids *ids, int id)
+{
+ struct kern_ipc_perm *out;
+ int lid = ipcid_to_idx(id);
+
+ rcu_read_lock();
+ out = idr_find(&ids->ipcs_idr, lid);
+ if (out == NULL) {
+ rcu_read_unlock();
+ return ERR_PTR(-EINVAL);
+ }
+
+ spin_lock(&out->lock);
+
+ /*
+ * No need to verify that the structure is still valid since the
+ * rw_mutex is held.
+ */
+ return out;
+}
+
#ifdef __ARCH_WANT_IPC_PARSE_VERSION
}
/*
- * File positions: pos 0 -> header, pos n -> ipc id + 1.
- * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
+ * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
+ * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
*/
static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
{
* Take the lock - this will be released by the corresponding
* call to stop().
*/
- mutex_lock(&ids->mutex);
+ down_read(&ids->rw_mutex);
/* pos < 0 is invalid */
if (*pos < 0)
struct ipc_proc_iface *iface = iter->iface;
struct ipc_ids *ids;
- /* If we had a locked segment, release it */
+ /* If we had a locked structure, release it */
if (ipc && ipc != SEQ_START_TOKEN)
ipc_unlock(ipc);
ids = iter->ns->ids[iface->ids];
/* Release the lock we took in start() */
- mutex_unlock(&ids->mutex);
+ up_read(&ids->rw_mutex);
}
static int sysvipc_proc_show(struct seq_file *s, void *it)
git.samba.org / sfrench / cifs-2.6.git / blobdiff