X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=ipc%2Fshm.c;h=b5bae9d945b62103ad8924ecf17dee8ee18a728c;hb=0ea648441a189f6e3e90a25c74511738799a0c7a;hp=3f5b14365f33e54408c5e89d3b15aacbc2c1435b;hpb=867f503d580eafbcc342141bae53cf6a27d413b1;p=firefly-linux-kernel-4.4.55.git

diff --git a/ipc/shm.c b/ipc/shm.c
index 3f5b14365f33..b5bae9d945b6 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)
 {
@@ -231,76 +237,80 @@ 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))
+	if (shp->shm_creator != current)
 		return 0;
 
-	if (shp->shm_cprid != task_tgid_vnr(current)) {
-		shm_unlock(shp);
+	/*
+	 * 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)
 		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);
-	struct task_struct *task;
-
-	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.
 	 *
-	 * XXX: the originating process may exist in another pid namespace.
+	 * As shp->* are changed under rw_mutex, it's safe to skip shp locking.
 	 */
-	task = find_task_by_vpid(shp->shm_cprid);
-	if (task != 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;
+	struct ipc_namespace *ns = task->nsproxy->ipc_ns;
 
-	if (!nsp)
-		return;
-	ns = nsp->ipc_ns;
-	if (!ns || !ns->shm_rmid_forced)
+	if (shm_ids(ns).in_use == 0)
 		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);
+	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);
 }
 
@@ -494,6 +504,7 @@ 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.