[PATCH] r/o bind mounts: get callers of vfs_mknod/create/mkdir()

[deliverable/linux.git] / fs / namei.c

diff --git a/fs/namei.c b/fs/namei.c
index 89ef3178eaaa48660ed487c9e5c67926ef175df8..3fbcf2021a2e5ac44181d569e4c03bad48379741 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1984,6 +1984,23 @@ int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
        return error;
 }
 
+static int may_mknod(mode_t mode)
+{
+       switch (mode & S_IFMT) {
+       case S_IFREG:
+       case S_IFCHR:
+       case S_IFBLK:
+       case S_IFIFO:
+       case S_IFSOCK:
+       case 0: /* zero mode translates to S_IFREG */
+               return 0;
+       case S_IFDIR:
+               return -EPERM;
+       default:
+               return -EINVAL;
+       }
+}
+
 asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
                                unsigned dev)
 {
@@ -2002,12 +2019,19 @@ asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
        if (error)
                goto out;
        dentry = lookup_create(&nd, 0);
-       error = PTR_ERR(dentry);
-
+       if (IS_ERR(dentry)) {
+               error = PTR_ERR(dentry);
+               goto out_unlock;
+       }
        if (!IS_POSIXACL(nd.path.dentry->d_inode))
                mode &= ~current->fs->umask;
-       if (!IS_ERR(dentry)) {
-               switch (mode & S_IFMT) {
+       error = may_mknod(mode);
+       if (error)
+               goto out_dput;
+       error = mnt_want_write(nd.path.mnt);
+       if (error)
+               goto out_dput;
+       switch (mode & S_IFMT) {
                case 0: case S_IFREG:
                        error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
                        break;
@@ -2018,14 +2042,11 @@ asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
                case S_IFIFO: case S_IFSOCK:
                        error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
                        break;
-               case S_IFDIR:
-                       error = -EPERM;
-                       break;
-               default:
-                       error = -EINVAL;
-               }
-               dput(dentry);
        }
+       mnt_drop_write(nd.path.mnt);
+out_dput:
+       dput(dentry);
+out_unlock:
        mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
        path_put(&nd.path);
 out:
@@ -2083,7 +2104,12 @@ asmlinkage long sys_mkdirat(int dfd, const char __user *pathname, int mode)
 
        if (!IS_POSIXACL(nd.path.dentry->d_inode))
                mode &= ~current->fs->umask;
+       error = mnt_want_write(nd.path.mnt);
+       if (error)
+               goto out_dput;
        error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
+       mnt_drop_write(nd.path.mnt);
+out_dput:
        dput(dentry);
 out_unlock:
        mutex_unlock(&nd.path.dentry->d_inode->i_mutex);