From b6f04d3d21458818073a2f5af5339f958864bf71 Mon Sep 17 00:00:00 2001 From: Yann Droneaud Date: Mon, 5 May 2014 19:33:23 +0200 Subject: [PATCH] RDMA/cxgb4: Add missing padding at end of struct c4iw_create_cq_resp The i386 ABI disagrees with most other ABIs regarding alignment of data types 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 c4iw_create_cq_resp gets implicitly 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 c4iw_create_cq_resp \ drivers/infiniband/hw/cxgb4/iw_cxgb4.o Then, structure layout can be compared between i386 and x86_64: +++ obj-i386/drivers/infiniband/hw/cxgb4/iw_cxgb4.o.pahole.txt 2014-03-28 11:43:05.547432195 +0100 --- obj-x86_64/drivers/infiniband/hw/cxgb4/iw_cxgb4.o.pahole.txt 2014-03-28 10:55:10.990133017 +0100 @@ -14,9 +13,8 @@ struct c4iw_create_cq_resp { __u32 size; /* 28 4 */ __u32 qid_mask; /* 32 4 */ - /* size: 36, cachelines: 1, members: 6 */ - /* last cacheline: 36 bytes */ + /* size: 40, cachelines: 1, members: 6 */ + /* padding: 4 */ + /* last cacheline: 40 bytes */ }; This ABI disagreement will make an x86_64 kernel try to write past the buffer provided by an i386 binary. When boundary check will be implemented, the x86_64 kernel will refuse to write past the i386 userspace provided buffer and the uverbs will fail. If the structure is on a page boundary and the next page is not mapped, ib_copy_to_udata() will fail and the uverb will fail. This patch adds an explicit padding at end of structure c4iw_create_cq_resp, and, like 92b0ca7cb149 ("IB/mlx5: Fix stack info leak in mlx5_ib_alloc_ucontext()"), makes function c4iw_create_cq() not writting this padding field to userspace. This way, x86_64 kernel will be able to write struct c4iw_create_cq_resp as expected by unpatched and patched i386 libcxgb4. Link: http://marc.info/?i=cover.1399309513.git.ydroneaud@opteya.com Cc: Fixes: cfdda9d764362 ("RDMA/cxgb4: Add driver for Chelsio T4 RNIC") Fixes: e24a72a3302a6 ("RDMA/cxgb4: Fix four byte info leak in c4iw_create_cq()") Cc: Dan Carpenter Signed-off-by: Yann Droneaud Acked-by: Steve Wise Signed-off-by: Roland Dreier --- drivers/infiniband/hw/cxgb4/cq.c | 4 ++-- drivers/infiniband/hw/cxgb4/user.h | 1 + 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/infiniband/hw/cxgb4/cq.c b/drivers/infiniband/hw/cxgb4/cq.c index cfaa56a..7151a02 100644 --- a/drivers/infiniband/hw/cxgb4/cq.c +++ b/drivers/infiniband/hw/cxgb4/cq.c @@ -940,7 +940,6 @@ struct ib_cq *c4iw_create_cq(struct ib_device *ibdev, int entries, if (!mm2) goto err4; - memset(&uresp, 0, sizeof(uresp)); uresp.qid_mask = rhp->rdev.cqmask; uresp.cqid = chp->cq.cqid; uresp.size = chp->cq.size; @@ -951,7 +950,8 @@ struct ib_cq *c4iw_create_cq(struct ib_device *ibdev, int entries, uresp.gts_key = ucontext->key; ucontext->key += PAGE_SIZE; spin_unlock(&ucontext->mmap_lock); - ret = ib_copy_to_udata(udata, &uresp, sizeof uresp); + ret = ib_copy_to_udata(udata, &uresp, + sizeof(uresp) - sizeof(uresp.reserved)); if (ret) goto err5; diff --git a/drivers/infiniband/hw/cxgb4/user.h b/drivers/infiniband/hw/cxgb4/user.h index 11ccd27..9b7534b 100644 --- a/drivers/infiniband/hw/cxgb4/user.h +++ b/drivers/infiniband/hw/cxgb4/user.h @@ -48,6 +48,7 @@ struct c4iw_create_cq_resp { __u32 cqid; __u32 size; __u32 qid_mask; + __u32 reserved; /* explicit padding (optional for i386) */ }; -- 2.7.4