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-rw-r--r--ipc/shm.c97
1 files changed, 93 insertions, 4 deletions
diff --git a/ipc/shm.c b/ipc/shm.c
index 27884ad..3f5b143 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -74,6 +74,7 @@ void shm_init_ns(struct ipc_namespace *ns)
ns->shm_ctlmax = SHMMAX;
ns->shm_ctlall = SHMALL;
ns->shm_ctlmni = SHMMNI;
+ ns->shm_rmid_forced = 0;
ns->shm_tot = 0;
ipc_init_ids(&shm_ids(ns));
}
@@ -187,6 +188,23 @@ static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
}
/*
+ * shm_may_destroy - identifies whether shm segment should be destroyed now
+ *
+ * Returns true if and only if there are no active users of the segment and
+ * one of the following is true:
+ *
+ * 1) shmctl(id, IPC_RMID, NULL) was called for this shp
+ *
+ * 2) sysctl kernel.shm_rmid_forced is set to 1.
+ */
+static bool shm_may_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
+{
+ return (shp->shm_nattch == 0) &&
+ (ns->shm_rmid_forced ||
+ (shp->shm_perm.mode & SHM_DEST));
+}
+
+/*
* remove the attach descriptor vma.
* free memory for segment if it is marked destroyed.
* The descriptor has already been removed from the current->mm->mmap list
@@ -206,11 +224,83 @@ static void shm_close(struct vm_area_struct *vma)
shp->shm_lprid = task_tgid_vnr(current);
shp->shm_dtim = get_seconds();
shp->shm_nattch--;
- if(shp->shm_nattch == 0 &&
- shp->shm_perm.mode & SHM_DEST)
+ if (shm_may_destroy(ns, shp))
+ shm_destroy(ns, shp);
+ else
+ shm_unlock(shp);
+ up_write(&shm_ids(ns).rw_mutex);
+}
+
+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);
+
+ if (IS_ERR(shp))
+ return 0;
+
+ if (shp->shm_cprid != task_tgid_vnr(current)) {
+ shm_unlock(shp);
+ return 0;
+ }
+
+ if (shm_may_destroy(ns, shp))
+ shm_destroy(ns, shp);
+ else
+ shm_unlock(shp);
+ return 0;
+}
+
+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);
+ struct task_struct *task;
+
+ if (IS_ERR(shp))
+ return 0;
+
+ /*
+ * We want to destroy segments without users and with already
+ * exit'ed originating process.
+ *
+ * XXX: the originating process may exist in another pid namespace.
+ */
+ task = find_task_by_vpid(shp->shm_cprid);
+ if (task != NULL) {
+ shm_unlock(shp);
+ return 0;
+ }
+
+ if (shm_may_destroy(ns, 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);
+ 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 || !ns->shm_rmid_forced)
+ return;
+
+ /* 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);
up_write(&shm_ids(ns).rw_mutex);
}
@@ -950,8 +1040,7 @@ out_nattch:
shp = shm_lock(ns, shmid);
BUG_ON(IS_ERR(shp));
shp->shm_nattch--;
- if(shp->shm_nattch == 0 &&
- shp->shm_perm.mode & SHM_DEST)
+ if (shm_may_destroy(ns, shp))
shm_destroy(ns, shp);
else
shm_unlock(shp);
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