On Thu, Jun 17, 2021 at 05:36:49PM +0200, Christoph Hellwig wrote:
[..]
> +static int __init try_mount_nodev(char *fstype)
> +{
> + struct file_system_type *fs = get_fs_type(fstype);
> + int err = -EINVAL;
> +
> + if (!fs)
> + return -EINVAL;
> + if (!(fs->fs_flags & (FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA)))
Not sure what FS_BINARY_MOUNTDATA is why fs should not have that set. nfs
seems to set it too. So that means they can't use try_mount_nodev().
> + err = do_mount_root(root_device_name, fstype, root_mountflags,
> + root_mount_data);
> + put_filesystem(fs);
> +
> + if (err != -EACCES && err != -EINVAL)
In case of success err == 0, but we still panic(). We will need to
check for success as well.
if (err && err != -EACCES && err != -EINVAL)
> + panic("VFS: Unable to mount root \"%s\" (%s), err=%d\n",
> + root_device_name, fstype, err);
> + return err;
> +}
> +
> +static int __init mount_nodev_root(void)
> +{
> + char *fs_names, *p;
> + int err = -EINVAL;
> +
> + fs_names = (void *)__get_free_page(GFP_KERNEL);
> + if (!fs_names)
> + return -EINVAL;
> + split_fs_names(fs_names, root_fs_names);
root_fs_names can be NULL and it crashes with NULL pointer dereference.
Vivek
> +
> + for (p = fs_names; *p; p += strlen(p) + 1) {
> + err = try_mount_nodev(p);
> + if (!err)
> + break;
> + }
> +
> + free_page((unsigned long)fs_names);
> + return err;
> +}
> +
> void __init mount_root(void)
> {
> #ifdef CONFIG_ROOT_NFS
> @@ -550,6 +588,8 @@ void __init mount_root(void)
> return;
> }
> #endif
> + if (ROOT_DEV == 0 && mount_nodev_root() == 0)
> + return;
> #ifdef CONFIG_BLOCK
> {
> int err = create_dev("/dev/root", ROOT_DEV);
> --
> 2.30.2
>
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