linux-kernel - Re: [PATCH v3 1/4] ext4: add EXT4_INODE_HAS_XATTR

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Message-ID: <20220616100610.y36iqovyynckhee7@quack3.lan>
Date:   Thu, 16 Jun 2022 12:06:10 +0200
From:   Jan Kara <jack@...e.cz>
To:     Baokun Li <libaokun1@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com,
        lczerner@...hat.com, enwlinux@...il.com,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yebin10@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v3 1/4] ext4: add EXT4_INODE_HAS_XATTR_SPACE macro in
 xattr.h

On Thu 16-06-22 10:13:55, Baokun Li wrote:
> When adding an xattr to an inode, we must ensure that the inode_size is
> not less than EXT4_GOOD_OLD_INODE_SIZE + extra_isize + pad. Otherwise,
> the end position may be greater than the start position, resulting in UAF.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

Looks good. Feel free to add:

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

								Honza

> ---
>  fs/ext4/xattr.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
> index 77efb9a627ad..f885f362add4 100644
> --- a/fs/ext4/xattr.h
> +++ b/fs/ext4/xattr.h
> @@ -95,6 +95,19 @@ struct ext4_xattr_entry {
>  
>  #define EXT4_ZERO_XATTR_VALUE ((void *)-1)
>  
> +/*
> + * If we want to add an xattr to the inode, we should make sure that
> + * i_extra_isize is not 0 and that the inode size is not less than
> + * EXT4_GOOD_OLD_INODE_SIZE + extra_isize + pad.
> + *   EXT4_GOOD_OLD_INODE_SIZE   extra_isize header   entry   pad  data
> + * |--------------------------|------------|------|---------|---|-------|
> + */
> +#define EXT4_INODE_HAS_XATTR_SPACE(inode)				\
> +	((EXT4_I(inode)->i_extra_isize != 0) &&				\
> +	 (EXT4_GOOD_OLD_INODE_SIZE + EXT4_I(inode)->i_extra_isize +	\
> +	  sizeof(struct ext4_xattr_ibody_header) + EXT4_XATTR_PAD <=	\
> +	  EXT4_INODE_SIZE((inode)->i_sb)))
> +
>  struct ext4_xattr_info {
>  	const char *name;
>  	const void *value;
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR