From a8237b32a3faab155a5dc8f886452147ce73da3e Mon Sep 17 00:00:00 2001 From: Yann Droneaud Date: Mon, 5 May 2014 19:33:21 +0200 Subject: 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: Fixes: e126ba97dba9e ("mlx5: Add driver for Mellanox Connect-IB adapter") Signed-off-by: Yann Droneaud Signed-off-by: Roland Dreier --- drivers/infiniband/hw/mlx5/user.h | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/infiniband/hw/mlx5/user.h') diff --git a/drivers/infiniband/hw/mlx5/user.h b/drivers/infiniband/hw/mlx5/user.h index 0f4f8e4..d44ecd2 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 { -- cgit v1.1