linux-ext4 - Re: [PATCH] ext4: fix inode use after free in ext4_end_io_rsv

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Message-ID: <6c2445e9-5105-495f-a64a-3d6b1fb81a5f@huaweicloud.com>
Date: Thu, 10 Jul 2025 16:30:22 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: libaokun@...weicloud.com, linux-ext4@...r.kernel.org
Cc: tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz,
 linux-kernel@...r.kernel.org, yangerkun@...wei.com, libaokun1@...wei.com
Subject: Re: [PATCH] ext4: fix inode use after free in ext4_end_io_rsv_work()

On 2025/7/8 19:15, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> In ext4_io_end_defer_completion(), check if io_end->list_vec is empty to
> avoid adding an io_end that requires no conversion to the
> i_rsv_conversion_list, which in turn prevents starting an unnecessary
> worker. An ext4_emergency_state() check is also added to avoid attempting
> to abort the journal in an emergency state.
> 
> Additionally, ext4_put_io_end_defer() is refactored to call
> ext4_io_end_defer_completion() directly instead of being open-coded.
> This also prevents starting an unnecessary worker when EXT4_IO_END_FAILED
> is set but data_err=abort is not enabled.
> 
> This ensures that the check in ext4_put_io_end_defer() is consistent with
> the check in ext4_end_bio(). Otherwise, we might add an io_end to the
> i_rsv_conversion_list and then call ext4_finish_bio(), after which the
> inode could be freed before ext4_end_io_rsv_work() is called, triggering
> a use-after-free issue.
> 
> Fixes: ce51afb8cc5e ("ext4: abort journal on data writeback failure if in data_err=abort mode")
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

Looks good to me.

Reviewed-by: Zhang Yi <yi.zhang@...wei.com>

> ---
>  fs/ext4/page-io.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 179e54f3a3b6..3d8b0f6d2dea 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -236,10 +236,12 @@ static void dump_completed_IO(struct inode *inode, struct list_head *head)
>  
>  static bool ext4_io_end_defer_completion(ext4_io_end_t *io_end)
>  {
> -	if (io_end->flag & EXT4_IO_END_UNWRITTEN)
> +	if (io_end->flag & EXT4_IO_END_UNWRITTEN &&
> +	    !list_empty(&io_end->list_vec))
>  		return true;
>  	if (test_opt(io_end->inode->i_sb, DATA_ERR_ABORT) &&
> -	    io_end->flag & EXT4_IO_END_FAILED)
> +	    io_end->flag & EXT4_IO_END_FAILED &&
> +	    !ext4_emergency_state(io_end->inode->i_sb))
>  		return true;
>  	return false;
>  }
> @@ -256,6 +258,7 @@ static void ext4_add_complete_io(ext4_io_end_t *io_end)
>  	WARN_ON(!(io_end->flag & EXT4_IO_END_DEFER_COMPLETION));
>  	WARN_ON(io_end->flag & EXT4_IO_END_UNWRITTEN &&
>  		!io_end->handle && sbi->s_journal);
> +	WARN_ON(!io_end->bio);
>  
>  	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
>  	wq = sbi->rsv_conversion_wq;
> @@ -318,12 +321,9 @@ ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
>  void ext4_put_io_end_defer(ext4_io_end_t *io_end)
>  {
>  	if (refcount_dec_and_test(&io_end->count)) {
> -		if (io_end->flag & EXT4_IO_END_FAILED ||
> -		    (io_end->flag & EXT4_IO_END_UNWRITTEN &&
> -		     !list_empty(&io_end->list_vec))) {
> -			ext4_add_complete_io(io_end);
> -			return;
> -		}
> +		if (ext4_io_end_defer_completion(io_end))
> +			return ext4_add_complete_io(io_end);
> +
>  		ext4_release_io_end(io_end);
>  	}
>  }