Commits
Yann Droneaud committed a8237b32a3f
IB/mlx5: add missing padding at end of struct mlx5_ib_create_cq
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 ABI struct mlx5_ib_create_cq get padded to be aligned on a
8 bytes multiple, while for i386, such padding is not added.
The tool pahole can 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 lies 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/?i=cover.1399309513.git.ydroneaud@opteya.com
Cc: <stable@vger.kernel.org>
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>