From: Kees Cook <keescook@chromium.org>
Date: Thu, 1 Jul 2021 15:44:07 +0000 (+0200)
Subject: s390: iucv: Avoid field over-reading memcpy()
X-Git-Tag: microblaze-v5.16~446^2~59
X-Git-Url: http://git.monstr.eu/?p=linux-2.6-microblaze.git;a=commitdiff_plain;h=5140aaa4604ba96685dc04b4d2dde3384bbaecef

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 349c6ac3313f..e6795d5a546a 100644
--- 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);
 	}