Messages in this thread | | | Date | Thu, 29 Jul 2021 18:39:22 -0700 | From | Kees Cook <> | Subject | Re: [PATCH 62/64] netlink: Avoid false-positive memcpy() warning |
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On Wed, Jul 28, 2021 at 01:24:01PM +0200, Rasmus Villemoes wrote: > On 28/07/2021 07.49, Greg Kroah-Hartman wrote: > > On Tue, Jul 27, 2021 at 01:58:53PM -0700, Kees Cook wrote: > >> In preparation for FORTIFY_SOURCE performing compile-time and run-time > >> field bounds checking for memcpy(), memmove(), and memset(), avoid > >> intentionally writing across neighboring fields. > >> > >> Add a flexible array member to mark the end of struct nlmsghdr, and > >> split the memcpy() to avoid false positive memcpy() warning: > >> > >> memcpy: detected field-spanning write (size 32) of single field (size 16) > >> > >> Signed-off-by: Kees Cook <keescook@chromium.org> > >> --- > >> include/uapi/linux/netlink.h | 1 + > >> net/netlink/af_netlink.c | 4 +++- > >> 2 files changed, 4 insertions(+), 1 deletion(-) > >> > >> diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h > >> index 4c0cde075c27..ddeaa748df5e 100644 > >> --- a/include/uapi/linux/netlink.h > >> +++ b/include/uapi/linux/netlink.h > >> @@ -47,6 +47,7 @@ struct nlmsghdr { > >> __u16 nlmsg_flags; /* Additional flags */ > >> __u32 nlmsg_seq; /* Sequence number */ > >> __u32 nlmsg_pid; /* Sending process port ID */ > >> + __u8 contents[]; > > > > Is this ok to change a public, userspace visable, structure? > > At least it should keep using a nlmsg_ prefix for consistency and reduce > risk of collision with somebody having defined an object-like contents > macro. But there's no guarantees in any case, of course.
Ah, good call. I've adjusted this and added a comment.
Thanks!
-Kees
-- Kees Cook
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