Re: [PATCH v2 1/3] libceph: fix unaligned accesses in ceph_entity_addr handling

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On Thu, May 2, 2019 at 8:46 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> GCC9 is throwing a lot of warnings about unaligned access. This patch
> fixes some of them by changing most of the sockaddr handling functions
> to take a pointer to struct ceph_entity_addr instead of struct
> sockaddr_storage.  The lower functions can then take copies or do
> unaligned accesses as needed.

Linus has disabled this warning in 5.1 [1], but these look real to me,
at least when sockaddr_storage is coming from ceph_entity_inst.  I'd be
happier if we defined non-packed variants of ceph_entity_addr and
ceph_entity_inst and used them throughout the code, but that's likely
a lot more churn.  I might take a stab at it just to see how it goes...

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6f303d60534c46aa1a239f29c321f95c83dda748

>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
>  net/ceph/messenger.c | 77 ++++++++++++++++++++++----------------------
>  1 file changed, 38 insertions(+), 39 deletions(-)
>
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 3083988ce729..54713836cac3 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -449,7 +449,7 @@ static void set_sock_callbacks(struct socket *sock,
>   */
>  static int ceph_tcp_connect(struct ceph_connection *con)
>  {
> -       struct sockaddr_storage *paddr = &con->peer_addr.in_addr;
> +       struct sockaddr_storage addr = con->peer_addr.in_addr;

Probably worth a comment, even something as short as /* align */.

>         struct socket *sock;
>         unsigned int noio_flag;
>         int ret;
> @@ -458,7 +458,7 @@ static int ceph_tcp_connect(struct ceph_connection *con)
>
>         /* sock_create_kern() allocates with GFP_KERNEL */
>         noio_flag = memalloc_noio_save();
> -       ret = sock_create_kern(read_pnet(&con->msgr->net), paddr->ss_family,
> +       ret = sock_create_kern(read_pnet(&con->msgr->net), addr.ss_family,
>                                SOCK_STREAM, IPPROTO_TCP, &sock);
>         memalloc_noio_restore(noio_flag);
>         if (ret)
> @@ -474,7 +474,7 @@ static int ceph_tcp_connect(struct ceph_connection *con)
>         dout("connect %s\n", ceph_pr_addr(&con->peer_addr.in_addr));
>
>         con_sock_state_connecting(con);
> -       ret = sock->ops->connect(sock, (struct sockaddr *)paddr, sizeof(*paddr),
> +       ret = sock->ops->connect(sock, (struct sockaddr *)&addr, sizeof(addr),
>                                  O_NONBLOCK);
>         if (ret == -EINPROGRESS) {
>                 dout("connect %s EINPROGRESS sk_state = %u\n",
> @@ -1795,12 +1795,13 @@ static int verify_hello(struct ceph_connection *con)
>         return 0;
>  }
>
> -static bool addr_is_blank(struct sockaddr_storage *ss)
> +static bool addr_is_blank(struct ceph_entity_addr *ea)
>  {
> -       struct in_addr *addr = &((struct sockaddr_in *)ss)->sin_addr;
> -       struct in6_addr *addr6 = &((struct sockaddr_in6 *)ss)->sin6_addr;
> +       struct sockaddr_storage ss = ea->in_addr;

Same here.

> +       struct in_addr *addr = &((struct sockaddr_in *)&ss)->sin_addr;
> +       struct in6_addr *addr6 = &((struct sockaddr_in6 *)&ss)->sin6_addr;
>
> -       switch (ss->ss_family) {
> +       switch (ss.ss_family) {
>         case AF_INET:
>                 return addr->s_addr == htonl(INADDR_ANY);
>         case AF_INET6:
> @@ -1810,25 +1811,27 @@ static bool addr_is_blank(struct sockaddr_storage *ss)
>         }
>  }
>
> -static int addr_port(struct sockaddr_storage *ss)
> +static int addr_port(struct ceph_entity_addr *ea)
>  {
> -       switch (ss->ss_family) {
> +       struct sockaddr_storage ss = ea->in_addr;
> +
> +       switch (ss.ss_family) {
>         case AF_INET:
> -               return ntohs(((struct sockaddr_in *)ss)->sin_port);
> +               return ntohs(((struct sockaddr_in *)&ss)->sin_port);
>         case AF_INET6:
> -               return ntohs(((struct sockaddr_in6 *)ss)->sin6_port);
> +               return ntohs(((struct sockaddr_in6 *)&ss)->sin6_port);
>         }
>         return 0;
>  }

Can we do the get_unaligned() dance instead of copying here?

Thanks,

                Ilya



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