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Date:   Wed, 29 Jun 2022 14:40:51 +0200
From:   Jan Kara <jack@suse.cz>
To:     Zhang Yi <yi.zhang@huawei.com>
Cc:     linux-ext4@vger.kernel.org, tytso@mit.edu,
        adilger.kernel@dilger.ca, jack@suse.cz, yukuai3@huawei.com
Subject: Re: [PATCH v3 2/2] ext4: check and assert if marking an no_delete
 evicting inode dirty
Message-ID: <20220629124051.qpc2voxvzbyhir3y@quack3.lan>
References: <20220629112647.4141034-1-yi.zhang@huawei.com>
 <20220629112647.4141034-2-yi.zhang@huawei.com>
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On Wed 29-06-22 19:26:47, Zhang Yi wrote:
> In ext4_evict_inode(), if we evicting an inode in the 'no_delete' path,
> it cannot be raced by another mark_inode_dirty(). If it happens,
> someone else may accidentally dirty it without holding inode refcount
> and probably cause use-after-free issues in the writeback procedure.
> It's indiscoverable and hard to debug, so add an WARN_ON_ONCE() to
> check and detect this issue in advance.
> 
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> ---
> v2->v3:
>  - Switch to use WARN_ON_ONCE instead of ASSERT.

Thanks! Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> 
>  fs/ext4/inode.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 702cc208689a..902393373152 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -333,6 +333,12 @@ void ext4_evict_inode(struct inode *inode)
>  	ext4_xattr_inode_array_free(ea_inode_array);
>  	return;
>  no_delete:
> +	/*
> +	 * Check out some where else accidentally dirty the evicting inode,
> +	 * which may probably cause inode use-after-free issues later.
> +	 */
> +	WARN_ON_ONCE(!list_empty_careful(&inode->i_io_list));
> +
>  	if (!list_empty(&EXT4_I(inode)->i_fc_list))
>  		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_NOMEM, NULL);
>  	ext4_clear_inode(inode);	/* We must guarantee clearing of inode... */
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR