linux-ext4 - Re: [PATCH 1/5] ext4: Fix EXT4_MAX_LOGICAL

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Message-ID: <20200423111636.GH3737@quack2.suse.cz>
Date:   Thu, 23 Apr 2020 13:16:36 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ritesh Harjani <riteshh@...ux.ibm.com>
Cc:     linux-ext4@...r.kernel.org, jack@...e.cz, tytso@....edu,
        adilger@...ger.ca, darrick.wong@...cle.com, hch@...radead.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Murphy Zhou <jencce.kernel@...il.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Amir Goldstein <amir73il@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-unionfs@...r.kernel.org,
        syzbot+77fa5bdb65cc39711820@...kaller.appspotmail.com
Subject: Re: [PATCH 1/5] ext4: Fix EXT4_MAX_LOGICAL_BLOCK macro

On Thu 23-04-20 16:17:53, Ritesh Harjani wrote:
> ext4 supports max number of logical blocks in a file to be 0xffffffff.
> (This is since ext4_extent's ee_block is __le32).
> This means that EXT4_MAX_LOGICAL_BLOCK should be 0xfffffffe (starting
> from 0 logical offset). This patch fixes this.
> 
> The issue was seen when ext4 moved to iomap_fiemap API and when
> overlayfs was mounted on top of ext4. Since overlayfs was missing
> filemap_check_ranges(), so it could pass a arbitrary huge length which
> lead to overflow of map.m_len logic.
> 
> This patch fixes that.
> 
> Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")
> Reported-by: syzbot+77fa5bdb65cc39711820@...kaller.appspotmail.com
> Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>

The patch looks good to me. You can add:

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

								Honza


> ---
>  fs/ext4/ext4.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 91eb4381cae5..ad2dbf6e4924 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -722,7 +722,7 @@ enum {
>  #define EXT4_MAX_BLOCK_FILE_PHYS	0xFFFFFFFF
>  
>  /* Max logical block we can support */
> -#define EXT4_MAX_LOGICAL_BLOCK		0xFFFFFFFF
> +#define EXT4_MAX_LOGICAL_BLOCK		0xFFFFFFFE
>  
>  /*
>   * Structure of an inode on the disk
> -- 
> 2.21.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR