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>

1 files changed, 16 insertions, 10 deletions

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 48526b935682..1cf498fd2b52 100644
--- 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 "