2 files changed, 129 insertions, 4 deletions

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 56410faa4550..00fba2bab87d 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -31,12 +31,37 @@ static int proc_ipc_dointvec(ctl_table *table, int write,
         void __user *buffer, size_t *lenp, loff_t *ppos)
 {
         struct ctl_table ipc_table;
+
         memcpy(&ipc_table, table, sizeof(ipc_table));
         ipc_table.data = get_ipc(table);
 
         return proc_dointvec(&ipc_table, write, buffer, lenp, ppos);
 }
 
+static int proc_ipc_dointvec_minmax(ctl_table *table, int write,
+        void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        struct ctl_table ipc_table;
+
+        memcpy(&ipc_table, table, sizeof(ipc_table));
+        ipc_table.data = get_ipc(table);
+
+        return proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);
+}
+
+static int proc_ipc_dointvec_minmax_orphans(ctl_table *table, int write,
+        void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+        int err = proc_ipc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+        if (err < 0)
+                return err;
+        if (ns->shm_rmid_forced)
+                shm_destroy_orphaned(ns);
+        return err;
+}
+
 static int proc_ipc_callback_dointvec(ctl_table *table, int write,
         void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -125,6 +150,8 @@ static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,
 #else
 #define proc_ipc_doulongvec_minmax NULL
 #define proc_ipc_dointvec          NULL
+#define proc_ipc_dointvec_minmax   NULL
+#define proc_ipc_dointvec_minmax_orphans   NULL
 #define proc_ipc_callback_dointvec NULL
 #define proc_ipcauto_dointvec_minmax NULL
 #endif
@@ -155,6 +182,15 @@ static struct ctl_table ipc_kern_table[] = {
                 .proc_handler   = proc_ipc_dointvec,
         },
         {
+                .procname       = "shm_rmid_forced",
+                .data           = &init_ipc_ns.shm_rmid_forced,
+                .maxlen         = sizeof(init_ipc_ns.shm_rmid_forced),
+                .mode           = 0644,
+                .proc_handler   = proc_ipc_dointvec_minmax_orphans,
+                .extra1         = &zero,
+                .extra2         = &one,
+        },
+        {
                 .procname       = "msgmax",
                 .data           = &init_ipc_ns.msg_ctlmax,
                 .maxlen         = sizeof (init_ipc_ns.msg_ctlmax),
diff --git a/ipc/shm.c b/ipc/shm.c
index 27884adb1a90..3f5b14365f33 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);