proc: make struct proc_dir_entry::name a terminal array rather than a pointer

Since __proc_create() appends the name it is given to the end of the PDE
structure that it allocates, there isn't a need to store a name pointer.
Instead we can just replace the name pointer with a terminal char array of
_unspecified_ length.  The compiler will simply append the string to statically
defined variables of PDE type overlapping any hole at the end of the structure
and, unlike specifying an explicitly _zero_ length array, won't give a warning
if you try to statically initialise it with a string of more than zero length.

Also, whilst we're at it:

 (1) Move namelen to end just prior to name and reduce it to a single byte
     (name shouldn't be longer than NAME_MAX).

 (2) Move pde_unload_lock two places further on so that if it's four bytes in
     size on a 64-bit machine, it won't cause an unused hole in the PDE struct.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 7 insertions, 8 deletions

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index f1637f17c37c..9d99131d0d65 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -620,8 +620,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
         if (!ent) goto out;
 
         memset(ent, 0, sizeof(struct proc_dir_entry));
-        memcpy(((char *) ent) + sizeof(struct proc_dir_entry), fn, len + 1);
-        ent->name = ((char *) ent) + sizeof(*ent);
+        memcpy(ent->name, fn, len + 1);
         ent->namelen = len;
         ent->mode = mode;
         ent->nlink = nlink;
diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 9020ac15baaa..f738024ccc8e 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -197,15 +197,15 @@ static __net_init int proc_net_ns_init(struct net *net)
         int err;
 
         err = -ENOMEM;
-        netd = kzalloc(sizeof(*netd), GFP_KERNEL);
+        netd = kzalloc(sizeof(*netd) + 4, GFP_KERNEL);
         if (!netd)
                 goto out;
 
         netd->data = net;
         netd->nlink = 2;
-        netd->name = "net";
         netd->namelen = 3;
         netd->parent = &proc_root;
+        memcpy(netd->name, "net", 4);
 
         err = -EEXIST;
         net_statd = proc_net_mkdir(net, "stat", netd);
diff --git a/fs/proc/root.c b/fs/proc/root.c
index d6c3b416529b..9a8a2b77b874 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -186,13 +186,13 @@ static const struct inode_operations proc_root_inode_operations = {
 struct proc_dir_entry proc_root = {
         .low_ino        = PROC_ROOT_INO, 
         .namelen        = 5, 
-        .name           = "/proc",
         .mode           = S_IFDIR | S_IRUGO | S_IXUGO, 
         .nlink          = 2, 
         .count          = ATOMIC_INIT(1),
         .proc_iops      = &proc_root_inode_operations, 
         .proc_fops      = &proc_root_operations,
         .parent         = &proc_root,
+        .name           = "/proc",
 };
 
 int pid_ns_prepare_proc(struct pid_namespace *ns)
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 650af6deaf8f..643b96c7a94f 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -50,8 +50,6 @@ typedef	int (write_proc_t)(struct file *file, const char __user *buffer,
 
 struct proc_dir_entry {
         unsigned int low_ino;
-        unsigned int namelen;
-        const char *name;
         mode_t mode;
         nlink_t nlink;
         uid_t uid;
@@ -73,9 +71,11 @@ struct proc_dir_entry {
         write_proc_t *write_proc;
         atomic_t count;         /* use count */
         int pde_users;  /* number of callers into module in progress */
-        spinlock_t pde_unload_lock; /* proc_fops checks and pde_users bumps */
         struct completion *pde_unload_completion;
         struct list_head pde_openers;   /* who did ->open, but not ->release */
+        spinlock_t pde_unload_lock; /* proc_fops checks and pde_users bumps */
+        u8 namelen;
+        char name[];
 };
 
 enum kcore_type {