[PATCH 3.12 027/170] IB/mlx5: add missing padding at end of struct mlx5_ib_create_srq

Jiri Slaby
2014-07-18T13:26:30Z

From: Yann Droneaud <ydroneaud@opteya.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

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: Jiri Slaby <jslaby@suse.cz>
---
drivers/infiniband/hw/mlx5/srq.c | 14 +++++++++++++-
drivers/infiniband/hw/mlx5/user.h | 1 +
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/mlx5/srq.c b/drivers/infiniband/hw/mlx5/srq.c
index 0aa478bc291a..47a1f0a9c926 100644
--- 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 e7da977e2548..84fea5d00cd2 100644
--- a/drivers/infiniband/hw/mlx5/user.h
+++ b/drivers/infiniband/hw/mlx5/user.h
@@ -100,6 +100,7 @@ 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 {
--
2.0.0