[PATCH v2 60/63] net/af_iucv: Use struct_group() to zero struct iucv_sock region

Kees Cook
2021-08-18T06:12:47Z

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark the region of struct iucv_sock that gets
initialized to zero. Avoid the future warning:

In function 'fortify_memset_chk',
inlined from 'iucv_sock_alloc' at net/iucv/af_iucv.c:476:2:
./include/linux/fortify-string.h:199:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
199 | __write_overflow_field(p_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: Julian Wiedmann <jwi@linux.ibm.com>
Cc: Karsten Graul <kgraul@linux.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-s390@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/net/iucv/af_iucv.h | 10 ++++++----
net/iucv/af_iucv.c | 2 +-
2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/net/iucv/af_iucv.h b/include/net/iucv/af_iucv.h
index ff06246dbbb9..df85d19fbf84 100644
--- a/include/net/iucv/af_iucv.h
+++ b/include/net/iucv/af_iucv.h
@@ -112,10 +112,12 @@ enum iucv_tx_notify {

struct iucv_sock {
struct sock sk;
- char src_user_id[8];
- char src_name[8];
- char dst_user_id[8];
- char dst_name[8];
+ struct_group(init,
+ char src_user_id[8];
+ char src_name[8];
+ char dst_user_id[8];
+ char dst_name[8];
+ );
struct list_head accept_q;
spinlock_t accept_q_lock;
struct sock *parent;
diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index 18316ee3c692..9446e2771d31 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -473,7 +473,7 @@ static struct sock *iucv_sock_alloc(struct socket *sock, int proto, gfp_t prio,
atomic_set(&iucv->msg_recv, 0);
iucv->path = NULL;
iucv->sk_txnotify = afiucv_hs_callback_txnotify;
- memset(&iucv->src_user_id , 0, 32);
+ memset(&iucv->init, 0, sizeof(iucv->init));
if (pr_iucv)
iucv->transport = AF_IUCV_TRANS_IUCV;
else
--
2.30.2