Messages in this thread | | | Date | Tue, 06 Feb 2018 11:19:49 -0500 (EST) | Subject | Re: [PATCH v2] socket: Provide put_cmsg_whitelist() for constant size copies | From | David Miller <> |
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From: Kees Cook <keescook@chromium.org> Date: Tue, 6 Feb 2018 04:31:50 +1100
> On Tue, Feb 6, 2018 at 2:03 AM, David Miller <davem@davemloft.net> wrote: >> From: Kees Cook <keescook@chromium.org> >> 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. > > It didn't look like put_cmsg() was on a fast path, so it seemed like a > bounce buffer was the best solution here (and it's not without > precedent).
For some things like timestamps it can be important.
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