[PATCH 4.19 19/32] tipc: Avoid copying bytes beyond the supplied data

Greg Kroah-Hartman
2019-06-03T09:10:11Z

From: Chris Packham <chris.packham@alliedtelesis.co.nz>

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];
^~~~~~~~~~~

We still want to ensure any padding bytes at the end are initialised, do
this with a explicit memset() rather than copy bytes past the end of
data. Apply the same logic to TCM_SET.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/uapi/linux/tipc_config.h | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/include/uapi/linux/tipc_config.h
+++ b/include/uapi/linux/tipc_config.h
@@ -307,8 +307,10 @@ static inline int TLV_SET(void *tlv, __u
tlv_ptr = (struct tlv_desc *)tlv;
tlv_ptr->tlv_type = htons(type);
tlv_ptr->tlv_len = htons(tlv_len);
- if (len && data)
- memcpy(TLV_DATA(tlv_ptr), data, tlv_len);
+ if (len && data) {
+ memcpy(TLV_DATA(tlv_ptr), data, len);
+ memset(TLV_DATA(tlv_ptr) + len, 0, TLV_SPACE(len) - tlv_len);
+ }
return TLV_SPACE(len);
}

@@ -405,8 +407,10 @@ static inline int TCM_SET(void *msg, __u
tcm_hdr->tcm_len = htonl(msg_len);
tcm_hdr->tcm_type = htons(cmd);
tcm_hdr->tcm_flags = htons(flags);
- if (data_len && data)
+ if (data_len && data) {
memcpy(TCM_DATA(msg), data, data_len);
+ memset(TCM_DATA(msg) + data_len, 0, TCM_SPACE(data_len) - msg_len);
+ }
return TCM_SPACE(data_len);
}