linux-kernel - Re: [PATCH -next, v2] audit: use struct

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Date:   Wed, 15 Dec 2021 16:00:04 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Xiu Jianfeng <xiujianfeng@...wei.com>
Cc:     paul@...l-moore.com, eparis@...hat.com, keescook@...omium.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH -next, v2] audit: use struct_size() helper in kmalloc()

On Wed, Dec 15, 2021 at 11:04:20AM +0800, Xiu Jianfeng wrote:
> Make use of struct_size() helper instead of an open-coded calculation.

I think you should also mention the flexible array transformation in
struct audit_rule_data.

Thanks
--
Gustavo

> 
> Link: https://github.com/KSPP/linux/issues/160
> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
> ---
>  include/uapi/linux/audit.h | 2 +-
>  kernel/audit.c             | 4 ++--
>  kernel/audit_tree.c        | 2 +-
>  kernel/auditfilter.c       | 4 ++--
>  4 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 9176a095fefc..8eda133ca4c1 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -514,7 +514,7 @@ struct audit_rule_data {
>  	__u32		values[AUDIT_MAX_FIELDS];
>  	__u32		fieldflags[AUDIT_MAX_FIELDS];
>  	__u32		buflen;	/* total length of string fields */
> -	char		buf[0];	/* string fields buffer */
> +	char		buf[];	/* string fields buffer */
>  };
>  
>  #endif /* _UAPI_LINUX_AUDIT_H_ */
> diff --git a/kernel/audit.c b/kernel/audit.c
> index d4084751cfe6..7778eca34837 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1446,7 +1446,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>  			if (err)
>  				return err;
>  		}
> -		sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL);
> +		sig_data = kmalloc(struct_size(sig_data, ctx, len), GFP_KERNEL);
>  		if (!sig_data) {
>  			if (audit_sig_sid)
>  				security_release_secctx(ctx, len);
> @@ -1459,7 +1459,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>  			security_release_secctx(ctx, len);
>  		}
>  		audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO, 0, 0,
> -				 sig_data, sizeof(*sig_data) + len);
> +				 sig_data, struct_size(sig_data, ctx, len));
>  		kfree(sig_data);
>  		break;
>  	case AUDIT_TTY_GET: {
> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index 72324afcffef..e7315d487163 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -94,7 +94,7 @@ static struct audit_tree *alloc_tree(const char *s)
>  {
>  	struct audit_tree *tree;
>  
> -	tree = kmalloc(sizeof(struct audit_tree) + strlen(s) + 1, GFP_KERNEL);
> +	tree = kmalloc(struct_size(tree, pathname, strlen(s) + 1), GFP_KERNEL);
>  	if (tree) {
>  		refcount_set(&tree->count, 1);
>  		tree->goner = 0;
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 4173e771650c..42d99896e7a6 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -637,7 +637,7 @@ static struct audit_rule_data *audit_krule_to_data(struct audit_krule *krule)
>  	void *bufp;
>  	int i;
>  
> -	data = kmalloc(sizeof(*data) + krule->buflen, GFP_KERNEL);
> +	data = kmalloc(struct_size(data, buf, krule->buflen), GFP_KERNEL);
>  	if (unlikely(!data))
>  		return NULL;
>  	memset(data, 0, sizeof(*data));
> @@ -1092,7 +1092,7 @@ static void audit_list_rules(int seq, struct sk_buff_head *q)
>  				break;
>  			skb = audit_make_reply(seq, AUDIT_LIST_RULES, 0, 1,
>  					       data,
> -					       sizeof(*data) + data->buflen);
> +					       struct_size(data, buf, data->buflen));
>  			if (skb)
>  				skb_queue_tail(q, skb);
>  			kfree(data);
> -- 
> 2.17.1
>