s390: iucv: Avoid field over-reading memcpy()

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

Add a wrapping struct to serve as the memcpy() source so the compiler
can perform appropriate bounds checking, avoiding this future warning:

In function '__fortify_memcpy',
    inlined from 'iucv_message_pending' at net/iucv/iucv.c:1663:4:
./include/linux/fortify-string.h:246:4: error: call to '__read_overflow2_field' declared with attribute error: detected read beyond size of field (2nd parameter)

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
index 349c6ac..e6795d5 100644 (file)
--- a/net/iucv/iucv.c
+++ b/net/iucv/iucv.c
@@ -1635,14 +1635,16 @@ struct iucv_message_pending {
        u8  iptype;
        u32 ipmsgid;
        u32 iptrgcls;
-       union {
-               u32 iprmmsg1_u32;
-               u8  iprmmsg1[4];
-       } ln1msg1;
-       union {
-               u32 ipbfln1f;
-               u8  iprmmsg2[4];
-       } ln1msg2;
+       struct {
+               union {
+                       u32 iprmmsg1_u32;
+                       u8  iprmmsg1[4];
+               } ln1msg1;
+               union {
+                       u32 ipbfln1f;
+                       u8  iprmmsg2[4];
+               } ln1msg2;
+       } rmmsg;
        u32 res1[3];
        u32 ipbfln2f;
        u8  ippollfg;
@@ -1660,10 +1662,10 @@ static void iucv_message_pending(struct iucv_irq_data *data)
                msg.id = imp->ipmsgid;
                msg.class = imp->iptrgcls;
                if (imp->ipflags1 & IUCV_IPRMDATA) {
-                       memcpy(msg.rmmsg, imp->ln1msg1.iprmmsg1, 8);
+                       memcpy(msg.rmmsg, &imp->rmmsg, 8);
                        msg.length = 8;
                } else
-                       msg.length = imp->ln1msg2.ipbfln1f;
+                       msg.length = imp->rmmsg.ln1msg2.ipbfln1f;
                msg.reply_size = imp->ipbfln2f;
                path->handler->message_pending(path, &msg);
        }