linux-kernel - Re: [PATCH 1/2] ima: check xattr value length in ima_inode

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Date:	Thu, 23 Oct 2014 17:40:07 +0200
From:	Jan Kara <jack@...e.cz>
To:	Dmitry Kasatkin <d.kasatkin@...sung.com>
Cc:	zohar@...ux.vnet.ibm.com, linux-security-module@...r.kernel.org,
	linux-ima-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, jack@...e.cz,
	dmitry.kasatkin@...il.com
Subject: Re: [PATCH 1/2] ima: check xattr value length in ima_inode_setxattr()

On Thu 23-10-14 16:47:17, Dmitry Kasatkin wrote:
> ima_inode_setxattr() can be called with no value. Function does not
> check the length so that following command can be used to produce
> kernel oops: setfattr -n security.ima FOO. This patch fixes it.
> 
..
> 
> Reported-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Dmitry Kasatkin <d.kasatkin@...sung.com>
> ---
>  security/integrity/ima/ima_appraise.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index 5b845af..f07aacd 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -378,6 +378,8 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
>  	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
>  				   xattr_value_len);
>  	if (result == 1) {
> +		if (!xattr_value_len)
> +			return -EINVAL;
  Wouldn't it be safer to return EINVAL whenever xattr_value_len !=
sizeof(evm_ima_xattr_data)?

								Honza
>  		ima_reset_appraise_flags(dentry->d_inode,
>  			 (xvalue->type == EVM_IMA_XATTR_DIGSIG) ? 1 : 0);
>  		result = 0;
> -- 
> 1.9.1
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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