Driver core: devtmpfs: prevent concurrent subdirectory creation and removal

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 48526b9..1cf498f 100644 (file)
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -32,6 +32,8 @@ static int dev_mount = 1;
 static int dev_mount;
 #endif
 
+static rwlock_t dirlock;
+
 static int __init mount_param(char *str)
 {
        dev_mount = simple_strtoul(str, NULL, 0);
@@ -86,16 +88,12 @@ static int dev_mkdir(const char *name, mode_t mode)
 
 static int create_path(const char *nodepath)
 {
-       char *path;
        struct nameidata nd;
        int err = 0;
 
-       path = kstrdup(nodepath, GFP_KERNEL);
-       if (!path)
-               return -ENOMEM;
-
+       read_lock(&dirlock);
        err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
-                             path, LOOKUP_PARENT, &nd);
+                             nodepath, LOOKUP_PARENT, &nd);
        if (err == 0) {
                struct dentry *dentry;
 
@@ -107,14 +105,17 @@ static int create_path(const char *nodepath)
                        dput(dentry);
                }
                mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
-
                path_put(&nd.path);
        } else if (err == -ENOENT) {
+               char *path;
                char *s;
 
                /* parent directories do not exist, create them */
+               path = kstrdup(nodepath, GFP_KERNEL);
+               if (!path)
+                       return -ENOMEM;
                s = path;
-               while (1) {
+               for (;;) {
                        s = strchr(s, '/');
                        if (!s)
                                break;
@@ -125,9 +126,10 @@ static int create_path(const char *nodepath)
                        s[0] = '/';
                        s++;
                }
+               kfree(path);
        }
+       read_unlock(&dirlock);
 
-       kfree(path);
        return err;
 }
 
@@ -234,7 +236,8 @@ static int delete_path(const char *nodepath)
        if (!path)
                return -ENOMEM;
 
-       while (1) {
+       write_lock(&dirlock);
+       for (;;) {
                char *base;
 
                base = strrchr(path, '/');
@@ -245,6 +248,7 @@ static int delete_path(const char *nodepath)
                if (err)
                        break;
        }
+       write_unlock(&dirlock);
 
        kfree(path);
        return err;
@@ -360,6 +364,8 @@ int __init devtmpfs_init(void)
        int err;
        struct vfsmount *mnt;
 
+       rwlock_init(&dirlock);
+
        err = register_filesystem(&dev_fs_type);
        if (err) {
                printk(KERN_ERR "devtmpfs: unable to register devtmpfs "