linux-ext4 - Re: [PATCH] ext4: Fix check for block being out of directory size

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Date:   Tue, 23 Aug 2022 12:00:19 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org,
        Salvatore Bonaccorso <carnil@...ian.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] ext4: Fix check for block being out of directory size

On Mon, Aug 22, 2022 at 01:48:32PM +0200, Jan Kara wrote:
> The check in __ext4_read_dirblock() for block being outside of directory
> size was wrong because it compared block number against directory size
> in bytes. Fix it.

Good catch, thanks!

Reviewed-by: Lukas Czerner <lczerner@...hat.com>

> 
> Fixes: 65f8ea4cd57d ("ext4: check if directory block is within i_size")
> CVE: CVE-2022-1184
> CC: stable@...r.kernel.org
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/namei.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 3a31b662f661..bc2e0612ec32 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -126,7 +126,7 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode,
>  	struct ext4_dir_entry *dirent;
>  	int is_dx_block = 0;
>  
> -	if (block >= inode->i_size) {
> +	if (block >= inode->i_size >> inode->i_blkbits) {
>  		ext4_error_inode(inode, func, line, block,
>  		       "Attempting to read directory block (%u) that is past i_size (%llu)",
>  		       block, inode->i_size);
> -- 
> 2.35.3
>