linux-kernel - [PATCH] RDMA/core: Use flexible array for mad data

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Message-Id: <20210616202615.1247242-1-keescook@chromium.org>
Date:   Wed, 16 Jun 2021 13:26:15 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Doug Ledford <dledford@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>, Jason Gunthorpe <jgg@...pe.ca>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-api@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] RDMA/core: Use flexible array for mad data

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

Without a flexible array, this looks like an attempt to perform a
memcpy() read beyond the end of the packet->mad.data array:

drivers/infiniband/core/user_mad.c:
	memcpy(packet->msg->mad, packet->mad.data, IB_MGMT_MAD_HDR);

Switch from [0] to [] to use the appropriately handled type for trailing
bytes.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/uapi/rdma/ib_user_mad.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/rdma/ib_user_mad.h b/include/uapi/rdma/ib_user_mad.h
index 90c0cf228020..10b5f6a4c677 100644
--- a/include/uapi/rdma/ib_user_mad.h
+++ b/include/uapi/rdma/ib_user_mad.h
@@ -143,7 +143,7 @@ struct ib_user_mad_hdr {
  */
 struct ib_user_mad {
 	struct ib_user_mad_hdr hdr;
-	__aligned_u64	data[0];
+	__aligned_u64	data[];
 };
 
 /*
-- 
2.25.1