linux-ext4 - Re: [PATCH 5.4.y 0/1] ext4: fix EXT4_MAX_LOGICAL

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Date:   Wed, 18 Aug 2021 09:47:33 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     George Kennedy <george.kennedy@...cle.com>
Cc:     tytso@....edu, adilger.kernel@...ger.ca, stable@...r.kernel.org,
        dhaval.giani@...cle.com, dan.carpenter@...cle.com,
        linux-ext4@...r.kernel.org, riteshh@...ux.ibm.com
Subject: Re: [PATCH 5.4.y 0/1] ext4: fix EXT4_MAX_LOGICAL_BLOCK macro

On Tue, Aug 17, 2021 at 04:12:11PM -0500, George Kennedy wrote:
> From: Ritesh Harjani <riteshh@...ux.ibm.com>
> 
> 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>
> Reviewed-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Christoph Hellwig <hch@....de>
> Link: https://lore.kernel.org/r/20200505154324.3226743-2-hch@lst.de
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> (cherry picked from commit 175efa81feb8405676e0136d97b10380179c92e0)
> Signed-off-by: George Kennedy <george.kennedy@...cle.com>
> ---
>  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 bf3eaa9..ae2cb15 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -718,7 +718,7 @@ 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
> -- 
> 1.8.3.1
> 

Now queued up, thanks.

greg k-h