IB/mlx5: add missing padding at end of struct mlx5_ib_create_srq

commit 43bc889380c2ad9aa230eccc03a15cc52cf710d4 upstream.

The i386 ABI disagrees with most other ABIs regarding alignment of
data type larger than 4 bytes: on most ABIs a padding must be added at
end of the structures, while it is not required on i386.

So for most ABIs struct mlx5_ib_create_srq gets implicitly padded to be
aligned on a 8 bytes multiple, while for i386, such padding is not
added.

Tool pahole could be used to find such implicit padding:

  $ pahole --anon_include \
           --nested_anon_include \
           --recursive \
           --class_name mlx5_ib_create_srq \
           drivers/infiniband/hw/mlx5/mlx5_ib.o

Then, structure layout can be compared between i386 and x86_64:

#  +++ obj-i386/drivers/infiniband/hw/mlx5/mlx5_ib.o.pahole.txt    2014-03-28 11:43:07.386413682 +0100
#  --- obj-x86_64/drivers/infiniband/hw/mlx5/mlx5_ib.o.pahole.txt  2014-03-27 13:06:17.788472721 +0100
#  @@ -69,7 +68,6 @@ struct mlx5_ib_create_srq {
#          __u64                      db_addr;              /*     8     8 */
#          __u32                      flags;                /*    16     4 */
#
#  -       /* size: 20, cachelines: 1, members: 3 */
#  -       /* last cacheline: 20 bytes */
#  +       /* size: 24, cachelines: 1, members: 3 */
#  +       /* padding: 4 */
#  +       /* last cacheline: 24 bytes */
#   };

ABI disagreement will make an x86_64 kernel try to read past
the buffer provided by an i386 binary.

When boundary check will be implemented, the x86_64 kernel will
refuse to read past the i386 userspace provided buffer and the
uverb will fail.

Anyway, if the structure lay in memory on a page boundary and
next page is not mapped, ib_copy_from_udata() will fail and the
uverb will fail.

This patch makes create_srq_user() takes care of the input
data size to handle the case where no padding was provided.

This way, x86_64 kernel will be able to handle struct mlx5_ib_create_srq
as sent by unpatched and patched i386 libmlx5.

Link: http://marc.info/?i=cover.1399309513.git.ydroneaud@opteya.com
Fixes: e126ba97dba9e ("mlx5: Add driver for Mellanox Connect-IB adapter")
Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/infiniband/hw/mlx5/srq.c b/drivers/infiniband/hw/mlx5/srq.c
index 210b3ea..384af6d 100644 (file)
--- a/drivers/infiniband/hw/mlx5/srq.c
+++ b/drivers/infiniband/hw/mlx5/srq.c
@@ -35,6 +35,7 @@
 #include <linux/mlx5/srq.h>
 #include <linux/slab.h>
 #include <rdma/ib_umem.h>
+#include <rdma/ib_user_verbs.h>
 
 #include "mlx5_ib.h"
 #include "user.h"
@@ -78,16 +79,27 @@ static int create_srq_user(struct ib_pd *pd, struct mlx5_ib_srq *srq,
 {
        struct mlx5_ib_dev *dev = to_mdev(pd->device);
        struct mlx5_ib_create_srq ucmd;
+       size_t ucmdlen;
        int err;
        int npages;
        int page_shift;
        int ncont;
        u32 offset;
 
-       if (ib_copy_from_udata(&ucmd, udata, sizeof(ucmd))) {
+       ucmdlen =
+               (udata->inlen - sizeof(struct ib_uverbs_cmd_hdr) <
+                sizeof(ucmd)) ? (sizeof(ucmd) -
+                                 sizeof(ucmd.reserved)) : sizeof(ucmd);
+
+       if (ib_copy_from_udata(&ucmd, udata, ucmdlen)) {
                mlx5_ib_dbg(dev, "failed copy udata\n");
                return -EFAULT;
        }
+
+       if (ucmdlen == sizeof(ucmd) &&
+           ucmd.reserved != 0)
+               return -EINVAL;
+
        srq->wq_sig = !!(ucmd.flags & MLX5_SRQ_FLAG_SIGNATURE);
 
        srq->umem = ib_umem_get(pd->uobject->context, ucmd.buf_addr, buf_size,

diff --git a/drivers/infiniband/hw/mlx5/user.h b/drivers/infiniband/hw/mlx5/user.h
index d44ecd2..d0ba264 100644 (file)
--- a/drivers/infiniband/hw/mlx5/user.h
+++ b/drivers/infiniband/hw/mlx5/user.h
@@ -110,6 +110,7 @@ struct mlx5_ib_create_srq {
        __u64   buf_addr;
        __u64   db_addr;
        __u32   flags;
+       __u32   reserved; /* explicit padding (optional on i386) */
 };
 
 struct mlx5_ib_create_srq_resp {