afs: Fix storage of cell names

The cell name stored in the afs_cell struct is a 64-char + NUL buffer -
when it needs to be able to handle up to AFS_MAXCELLNAME (256 chars) + NUL.

Fix this by changing the array to a pointer and allocating the string.

Found using Coverity.

Fixes: 989782dc ("afs: Overhaul cell database management")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/afs/cell.c

@@ -154,10 +154,17 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 		return ERR_PTR(-ENOMEM);
 	}
 
+	cell->name = kmalloc(namelen + 1, GFP_KERNEL);
+	if (!cell->name) {
+		kfree(cell);
+		return ERR_PTR(-ENOMEM);
+	}
+
 	cell->net = net;
 	cell->name_len = namelen;
 	for (i = 0; i < namelen; i++)
 		cell->name[i] = tolower(name[i]);
+	cell->name[i] = 0;
 
 	atomic_set(&cell->usage, 2);
 	INIT_WORK(&cell->manager, afs_manage_cell);
@@ -207,6 +214,7 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 	if (ret == -EINVAL)
 		printk(KERN_ERR "kAFS: bad VL server IP address\n");
 error:
+	kfree(cell->name);
 	kfree(cell);
 	_leave(" = %d", ret);
 	return ERR_PTR(ret);
@@ -489,6 +497,7 @@ static void afs_cell_destroy(struct rcu_head *rcu)
 	afs_put_vlserverlist(cell->net, rcu_access_pointer(cell->vl_servers));
 	afs_put_cell(cell->net, cell->alias_of);
 	key_put(cell->anonymous_key);
+	kfree(cell->name);
 	kfree(cell);
 
 	_leave(" [destroyed]");

fs/afs/internal.h

@@ -388,7 +388,7 @@ struct afs_cell {
 	struct afs_vlserver_list __rcu *vl_servers;
 
 	u8			name_len;	/* Length of name */
-	char			name[64 + 1];	/* Cell name, case-flattened and NUL-padded */
+	char			*name;		/* Cell name, case-flattened and NUL-padded */
 };
 
 /*