diff options
| -rw-r--r-- | ipc/shm.c | 61 |
1 files changed, 28 insertions, 33 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index fdaf8be65b75..9fb044f3b345 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -131,6 +131,12 @@ static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id) return container_of(ipcp, struct shmid_kernel, shm_perm); } +static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp) +{ + rcu_read_lock(); + spin_lock(&ipcp->shm_perm.lock); +} + static inline struct shmid_kernel *shm_lock_check(struct ipc_namespace *ns, int id) { @@ -231,18 +237,15 @@ static void shm_close(struct vm_area_struct *vma) up_write(&shm_ids(ns).rw_mutex); } +/* Called with ns->shm_ids(ns).rw_mutex locked */ static int shm_try_destroy_current(int id, void *p, void *data) { struct ipc_namespace *ns = data; - struct shmid_kernel *shp = shm_lock(ns, id); + struct kern_ipc_perm *ipcp = p; + struct shmid_kernel *shp = container_of(ipcp, struct shmid_kernel, shm_perm); - if (IS_ERR(shp)) - return 0; - - if (shp->shm_creator != current) { - shm_unlock(shp); + if (shp->shm_creator != current) return 0; - } /* * Mark it as orphaned to destroy the segment when @@ -255,64 +258,56 @@ static int shm_try_destroy_current(int id, void *p, void *data) * Don't even try to destroy it. If shm_rmid_forced=0 and IPC_RMID * is not set, it shouldn't be deleted here. */ - if (!ns->shm_rmid_forced) { - shm_unlock(shp); + if (!ns->shm_rmid_forced) return 0; - } - if (shm_may_destroy(ns, shp)) + if (shm_may_destroy(ns, shp)) { + shm_lock_by_ptr(shp); shm_destroy(ns, shp); - else - shm_unlock(shp); + } return 0; } +/* Called with ns->shm_ids(ns).rw_mutex locked */ static int shm_try_destroy_orphaned(int id, void *p, void *data) { struct ipc_namespace *ns = data; - struct shmid_kernel *shp = shm_lock(ns, id); - - if (IS_ERR(shp)) - return 0; + struct kern_ipc_perm *ipcp = p; + struct shmid_kernel *shp = container_of(ipcp, struct shmid_kernel, shm_perm); /* * We want to destroy segments without users and with already * exit'ed originating process. + * + * As shp->* are changed under rw_mutex, it's safe to skip shp locking. */ - if (shp->shm_creator != NULL) { - shm_unlock(shp); + if (shp->shm_creator != NULL) return 0; - } - if (shm_may_destroy(ns, shp)) + if (shm_may_destroy(ns, shp)) { + shm_lock_by_ptr(shp); shm_destroy(ns, shp); - else - shm_unlock(shp); + } return 0; } void shm_destroy_orphaned(struct ipc_namespace *ns) { down_write(&shm_ids(ns).rw_mutex); - idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns); + if (&shm_ids(ns).in_use) + idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns); up_write(&shm_ids(ns).rw_mutex); } void exit_shm(struct task_struct *task) { - struct nsproxy *nsp = task->nsproxy; - struct ipc_namespace *ns; - - if (!nsp) - return; - ns = nsp->ipc_ns; - if (!ns) - return; + struct ipc_namespace *ns = task->nsproxy->ipc_ns; /* Destroy all already created segments, but not mapped yet */ down_write(&shm_ids(ns).rw_mutex); - idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_current, ns); + if (&shm_ids(ns).in_use) + idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_current, ns); up_write(&shm_ids(ns).rw_mutex); } |