linux-kernel - [PATCH] tipc: Avoid copying bytes beyond the supplied data

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Message-Id: <20190502031004.7125-1-chris.packham@alliedtelesis.co.nz>
Date:   Thu,  2 May 2019 15:10:04 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     jon.maloy@...csson.com, ying.xue@...driver.com
Cc:     netdev@...r.kernel.org, tipc-discussion@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH] tipc: Avoid copying bytes beyond the supplied data

TLV_SET is called with a data pointer and a len parameter that tells us
how many bytes are pointed to by data. When invoking memcpy() we need
to careful to only copy len bytes.

Previously we would copy TLV_LENGTH(len) bytes which would copy an extra
4 bytes past the end of the data pointer which newer GCC versions
complain about.

 In file included from test.c:17:
 In function 'TLV_SET',
     inlined from 'test' at test.c:186:5:
 /usr/include/linux/tipc_config.h:317:3:
 warning: 'memcpy' forming offset [33, 36] is out of the bounds [0, 32]
 of object 'bearer_name' with type 'char[32]' [-Warray-bounds]
     memcpy(TLV_DATA(tlv_ptr), data, tlv_len);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 test.c: In function 'test':
 test.c::161:10: note:
 'bearer_name' declared here
     char bearer_name[TIPC_MAX_BEARER_NAME];
          ^~~~~~~~~~~

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---
 include/uapi/linux/tipc_config.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/tipc_config.h b/include/uapi/linux/tipc_config.h
index 4b2c93b1934c..f65c5b80ed33 100644
--- a/include/uapi/linux/tipc_config.h
+++ b/include/uapi/linux/tipc_config.h
@@ -308,7 +308,7 @@ static inline int TLV_SET(void *tlv, __u16 type, void *data, __u16 len)
 	tlv_ptr->tlv_type = htons(type);
 	tlv_ptr->tlv_len  = htons(tlv_len);
 	if (len && data)
-		memcpy(TLV_DATA(tlv_ptr), data, tlv_len);
+		memcpy(TLV_DATA(tlv_ptr), data, len);
 	return TLV_SPACE(len);
 }
 
-- 
2.21.0