2 files changed, 23 insertions, 7 deletions

diff --git a/include/linux/shm.h b/include/linux/shm.h
index 7d27ffde0190..92808b86703b 100644
--- a/include/linux/shm.h
+++ b/include/linux/shm.h
@@ -95,6 +95,9 @@ struct shmid_kernel /* private to the kernel */
         pid_t                   shm_cprid;
         pid_t                   shm_lprid;
         struct user_struct      *mlock_user;
+
+        /* The task created the shm object.  NULL if the task is dead. */
+        struct task_struct      *shm_creator;
 };
 
 /* shm_mode upper byte flags */
diff --git a/ipc/shm.c b/ipc/shm.c
index 3f5b14365f33..fdaf8be65b75 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -239,7 +239,23 @@ static int shm_try_destroy_current(int id, void *p, void *data)
         if (IS_ERR(shp))
                 return 0;
 
-        if (shp->shm_cprid != task_tgid_vnr(current)) {
+        if (shp->shm_creator != current) {
+                shm_unlock(shp);
+                return 0;
+        }
+
+        /*
+         * Mark it as orphaned to destroy the segment when
+         * kernel.shm_rmid_forced is changed.
+         * It is noop if the following shm_may_destroy() returns true.
+         */
+        shp->shm_creator = NULL;
+
+        /*
+         * 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);
                 return 0;
         }
@@ -255,7 +271,6 @@ 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;
@@ -263,11 +278,8 @@ static int shm_try_destroy_orphaned(int id, void *p, void *data)
         /*
          * 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) {
+        if (shp->shm_creator != NULL) {
                 shm_unlock(shp);
                 return 0;
         }
@@ -295,7 +307,7 @@ void exit_shm(struct task_struct *task)
         if (!nsp)
                 return;
         ns = nsp->ipc_ns;
-        if (!ns || !ns->shm_rmid_forced)
+        if (!ns)
                 return;
 
         /* Destroy all already created segments, but not mapped yet */
@@ -494,6 +506,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
         shp->shm_segsz = size;
         shp->shm_nattch = 0;
         shp->shm_file = file;
+        shp->shm_creator = current;
         /*
          * shmid gets reported as "inode#" in /proc/pid/maps.
          * proc-ps tools use this. Changing this will break them.