From: Kees Cook <keescook@xxxxxxxxxxxx>
Date: Fri, 2 Feb 2018 02:27:49 -0800
> @@ -343,6 +343,14 @@ struct ucred {
>
> extern int move_addr_to_kernel(void __user *uaddr, int ulen, struct sockaddr_storage *kaddr);
> extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
> +/*
> + * Provide a bounce buffer for copying cmsg data to userspace when the
> + * target memory isn't already whitelisted for hardened usercopy.
> + */
> +#define put_cmsg_whitelist(_msg, _level, _type, _ptr) ({ \
> + typeof(*(_ptr)) _val = *(_ptr); \
> + put_cmsg(_msg, _level, _type, sizeof(_val), &_val); \
> + })
I understand what you are trying to achieve, but it's at a real cost
here. Some of these objects are structures, for example the struct
sock_extended_err is 16 bytes.
And now we're going to copy it twice, once into the on-stack copy,
and then once again into the CMSG blob.
Please find a way to make hardened user copy happy without adding
new overhead.
Thank you.
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