diff options
Diffstat (limited to 'ipc/util.c')
| -rw-r--r-- | ipc/util.c | 78 |
1 files changed, 50 insertions, 28 deletions
diff --git a/ipc/util.c b/ipc/util.c index 49e75efe305..fd29246dc3c 100644 --- a/ipc/util.c +++ b/ipc/util.c @@ -194,7 +194,7 @@ void __init ipc_init_proc_interface(const char *path, const char *header, * Requires ipc_ids.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) @@ -258,10 +258,10 @@ 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 -1 is returned. * * Called with ipc_ids.mutex held. */ @@ -270,10 +270,6 @@ 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; @@ -303,12 +299,12 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size) /** * 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) @@ -330,9 +326,16 @@ int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, /** * 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.mutex and ipcp->lock held. */ static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops, struct ipc_params *params) @@ -353,12 +356,16 @@ static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops, /** * 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) @@ -389,6 +396,10 @@ int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, 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); @@ -401,12 +412,9 @@ int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, /** * 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. */ @@ -558,10 +566,12 @@ static void ipc_do_vfree(struct work_struct *work) */ 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); @@ -650,7 +660,7 @@ void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out) } /** - * 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 * @@ -669,6 +679,18 @@ void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out) out->seq = in->seq; } +/** + * ipc_lock - Lock an ipc structure + * @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. + * + * ipc_ids.mutex is not necessarily held before this function is called, + * that's why we enter a RCU read section. + * The ipc object is locked on exit. + */ + struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id) { struct kern_ipc_perm *out; @@ -771,8 +793,8 @@ static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos) } /* - * 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) { @@ -807,7 +829,7 @@ static void sysvipc_proc_stop(struct seq_file *s, void *it) 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); |