X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=ipc%2Fshm.c;fp=ipc%2Fshm.c;h=0bdf21c6814ef8118be3ae56196b85f11b7b3ac2;hb=a399b29dfbaaaf91162b2dc5a5875dd51bbfa2a1;hp=d69739610fd4384323004c46782116d54db6bbd5;hpb=30b0a105d9f7141e4cbf72ae5511832457d89788;p=~andy%2Flinux

diff --git a/ipc/shm.c b/ipc/shm.c
index d69739610fd..0bdf21c6814 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -208,15 +208,18 @@ static void shm_open(struct vm_area_struct *vma)
  */
 static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
 {
+	struct file *shm_file;
+
+	shm_file = shp->shm_file;
+	shp->shm_file = NULL;
 	ns->shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	shm_rmid(ns, shp);
 	shm_unlock(shp);
-	if (!is_file_hugepages(shp->shm_file))
-		shmem_lock(shp->shm_file, 0, shp->mlock_user);
+	if (!is_file_hugepages(shm_file))
+		shmem_lock(shm_file, 0, shp->mlock_user);
 	else if (shp->mlock_user)
-		user_shm_unlock(file_inode(shp->shm_file)->i_size,
-						shp->mlock_user);
-	fput (shp->shm_file);
+		user_shm_unlock(file_inode(shm_file)->i_size, shp->mlock_user);
+	fput(shm_file);
 	ipc_rcu_putref(shp, shm_rcu_free);
 }
 
@@ -983,6 +986,13 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 		}
 
 		shm_file = shp->shm_file;
+
+		/* check if shm_destroy() is tearing down shp */
+		if (shm_file == NULL) {
+			err = -EIDRM;
+			goto out_unlock0;
+		}
+
 		if (is_file_hugepages(shm_file))
 			goto out_unlock0;
 
@@ -1101,6 +1111,14 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
 		goto out_unlock;
 
 	ipc_lock_object(&shp->shm_perm);
+
+	/* check if shm_destroy() is tearing down shp */
+	if (shp->shm_file == NULL) {
+		ipc_unlock_object(&shp->shm_perm);
+		err = -EIDRM;
+		goto out_unlock;
+	}
+
 	path = shp->shm_file->f_path;
 	path_get(&path);
 	shp->shm_nattch++;