i386 ABI disagree 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 ABI struct mlx5_ib_create_cq get 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_cq \
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
@@ -34,9 +34,8 @@ struct mlx5_ib_create_cq {
__u64 db_addr; /* 8 8 */
__u32 cqe_size; /* 16 4 */
- /* size: 20, cachelines: 1, members: 3 */
- /* last cacheline: 20 bytes */
+ /* size: 24, cachelines: 1, members: 3 */
+ /* padding: 4 */
+ /* last cacheline: 24 bytes */
};
This 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, a 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 when
trying to read the 4 bytes of padding and the uverb will fail.
This patch makes create_cq_user() takes care of the input
data size to handle the case where no padding is provided.
This way, x86_64 kernel will be able to handle struct mlx5_ib_create_cq
as sent by unpatched and patched i386 libmlx5.
Link: http://marc.info/[email protected]
Cc: [email protected]
Fixes: e126ba97dba9e ('mlx5: Add driver for Mellanox Connect-IB adapter')
Signed-off-by: Yann Droneaud <[email protected]>
---
drivers/infiniband/hw/mlx5/cq.c | 13 +++++++++++--
drivers/infiniband/hw/mlx5/user.h | 1 +
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/infiniband/hw/mlx5/cq.c b/drivers/infiniband/hw/mlx5/cq.c
index 62bb6b49dc1d..5996132e799d 100644
--- a/drivers/infiniband/hw/mlx5/cq.c
+++ b/drivers/infiniband/hw/mlx5/cq.c
@@ -32,6 +32,7 @@
#include <linux/kref.h>
#include <rdma/ib_umem.h>
+#include <rdma/ib_user_verbs.h>
#include "mlx5_ib.h"
#include "user.h"
@@ -607,8 +608,16 @@ static int create_cq_user(struct mlx5_ib_dev *dev, struct
ib_udata *udata,
int ncont;
int err;
- if (ib_copy_from_udata(&ucmd, udata, sizeof(ucmd)))
- return -EFAULT;
+ if (udata->inlen - sizeof(struct ib_uverbs_cmd_hdr) < sizeof(ucmd)) {
+ if (ib_copy_from_udata(&ucmd, udata, sizeof(ucmd) -
sizeof(ucmd.reserved)))
+ return -EFAULT;
+ } else {
+ if (ib_copy_from_udata(&ucmd, udata, sizeof(ucmd)))
+ return -EFAULT;
+
+ if (ucmd.reserved != 0)
+ return -EINVAL;
+ }
if (ucmd.cqe_size != 64 && ucmd.cqe_size != 128)
return -EINVAL;
diff --git a/drivers/infiniband/hw/mlx5/user.h
b/drivers/infiniband/hw/mlx5/user.h
index 0f4f8e42a17f..d44ecd2c2faf 100644
--- a/drivers/infiniband/hw/mlx5/user.h
+++ b/drivers/infiniband/hw/mlx5/user.h
@@ -91,6 +91,7 @@ struct mlx5_ib_create_cq {
__u64 buf_addr;
__u64 db_addr;
__u32 cqe_size;
+ __u32 reserved; /* explicit padding (optional on i386) */
};
struct mlx5_ib_create_cq_resp {
--
1.9.0
--
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