Re: [PATCH] nilfs2: fix use-after-free bug of nilfs_root in nilfs_evict_inode()

[Andrew Morton]

On Wed, 10 May 2023 00:29:56 +0900 Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> wrote:

> During unmount process of nilfs2, nothing holds nilfs_root structure after
> nilfs2 detaches its writer in nilfs_detach_log_writer().  However, since
> nilfs_evict_inode() uses nilfs_root for some cleanup operations, it may
> cause use-after-free read if inodes are left in "garbage_list" and
> released by nilfs_dispose_list() at the end of nilfs_detach_log_writer().
> 
> Fix this issue by modifying nilfs_evict_inode() to only clear inode
> without additional metadata changes that use nilfs_root if the file system
> is degraded to read-only or the writer is detached.
> 
> ...
>
> --- a/fs/nilfs2/inode.c
> +++ b/fs/nilfs2/inode.c
> @@ -917,6 +917,7 @@ void nilfs_evict_inode(struct inode *inode)
>  	struct nilfs_transaction_info ti;
>  	struct super_block *sb = inode->i_sb;
>  	struct nilfs_inode_info *ii = NILFS_I(inode);
> +	struct the_nilfs *nilfs;
>  	int ret;

`the_nilfs' is unused - I'll zap it.