ipc,shm: move BUG_ON check into shm_lock

Upon every shm_lock call, we BUG_ON if an error was returned, indicating racing either in idr or in shm_destroy. Move this logic into the locking. [[email protected]: simplify code] Signed-off-by: Davidlohr Bueso <[email protected]> Cc: Manfred Spraul <[email protected]> Cc: Davidlohr Bueso <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
adn770 · Jul 1, 2015 · c5c8975 · c5c8975
1 parent c859aa8
commit c5c8975
Showing 1 changed file with 5 additions and 5 deletions.
diff --git a/ipc/shm.c b/ipc/shm.c
@@ -155,8 +155,11 @@ static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
 {
 	struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id);
 
-	if (IS_ERR(ipcp))
-		return (struct shmid_kernel *)ipcp;
+	/*
+	 * We raced in the idr lookup or with shm_destroy().  Either way, the
+	 * ID is busted.
+	 */
+	BUG_ON(IS_ERR(ipcp));
 
 	return container_of(ipcp, struct shmid_kernel, shm_perm);
 }
@@ -191,7 +194,6 @@ static void shm_open(struct vm_area_struct *vma)
 	struct shmid_kernel *shp;
 
 	shp = shm_lock(sfd->ns, sfd->id);
-	BUG_ON(IS_ERR(shp));
 	shp->shm_atim = get_seconds();
 	shp->shm_lprid = task_tgid_vnr(current);
 	shp->shm_nattch++;
@@ -258,7 +260,6 @@ static void shm_close(struct vm_area_struct *vma)
 	down_write(&shm_ids(ns).rwsem);
 	/* remove from the list of attaches of the shm segment */
 	shp = shm_lock(ns, sfd->id);
-	BUG_ON(IS_ERR(shp));
 	shp->shm_lprid = task_tgid_vnr(current);
 	shp->shm_dtim = get_seconds();
 	shp->shm_nattch--;
@@ -1191,7 +1192,6 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
 out_nattch:
 	down_write(&shm_ids(ns).rwsem);
 	shp = shm_lock(ns, shmid);
-	BUG_ON(IS_ERR(shp));
 	shp->shm_nattch--;
 	if (shm_may_destroy(ns, shp))
 		shm_destroy(ns, shp);