[PATCH 2/2] make shm_get_stat() more robust

[Tony Battersby <tonyb@cybernetics.com>]

shm_get_stat() assumes idr_find(&shm_ids(ns).ipcs_idr) returns
"struct shmid_kernel *"; all other callers assume that it returns
"struct kern_ipc_perm *".  This works because "struct kern_ipc_perm"
is currently the first member of "struct shmid_kernel", but it would
be better to use container_of() to prevent future breakage.

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
---
--- linux-2.6.29-rc2-git3/ipc/shm.c.orig	2009-01-27 16:23:10.000000000 -0500
+++ linux-2.6.29-rc2-git3/ipc/shm.c	2009-01-27 16:24:19.000000000 -0500
@@ -551,12 +551,14 @@ static void shm_get_stat(struct ipc_name
 	in_use = shm_ids(ns).in_use;
 
 	for (total = 0, next_id = 0; total < in_use; next_id++) {
+		struct kern_ipc_perm *ipc;
 		struct shmid_kernel *shp;
 		struct inode *inode;
 
-		shp = idr_find(&shm_ids(ns).ipcs_idr, next_id);
-		if (shp == NULL)
+		ipc = idr_find(&shm_ids(ns).ipcs_idr, next_id);
+		if (ipc == NULL)
 			continue;
+		shp = container_of(ipc, struct shmid_kernel, shm_perm);
 
 		inode = shp->shm_file->f_path.dentry->d_inode;