[PATCH AUTOSEL 5.10 050/176] flow_dissector: Fix out-of-bounds warnings

Sasha Levin
2021-09-09T12:40:27Z

From: "Gustavo A. R. Silva" <gustavoars@kernel.org>

[ Upstream commit 323e0cb473e2a8706ff162b6b4f4fa16023c9ba7 ]

Fix the following out-of-bounds warnings:

net/core/flow_dissector.c: In function '__skb_flow_dissect':
>> net/core/flow_dissector.c:1104:4: warning: 'memcpy' offset [24, 39] from the object at '<unknown>' is out of the bounds of referenced subobject 'saddr' with type 'struct in6_addr' at offset 8 [-Warray-bounds]
1104 | memcpy(&key_addrs->v6addrs, &iph->saddr,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1105 | sizeof(key_addrs->v6addrs));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from include/linux/ipv6.h:5,
from net/core/flow_dissector.c:6:
include/uapi/linux/ipv6.h:133:18: note: subobject 'saddr' declared here
133 | struct in6_addr saddr;
| ^~~~~
>> net/core/flow_dissector.c:1059:4: warning: 'memcpy' offset [16, 19] from the object at '<unknown>' is out of the bounds of referenced subobject 'saddr' with type 'unsigned int' at offset 12 [-Warray-bounds]
1059 | memcpy(&key_addrs->v4addrs, &iph->saddr,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1060 | sizeof(key_addrs->v4addrs));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from include/linux/ip.h:17,
from net/core/flow_dissector.c:5:
include/uapi/linux/ip.h:103:9: note: subobject 'saddr' declared here
103 | __be32 saddr;
| ^~~~~

The problem is that the original code is trying to copy data into a
couple of struct members adjacent to each other in a single call to
memcpy(). So, the compiler legitimately complains about it. As these
are just a couple of members, fix this by copying each one of them in
separate calls to memcpy().

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/109
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/d5ae2e65-1f18-2577-246f-bada7eee6ccd@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/flow_dissector.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index c52e5ea654e9..813c709c61cf 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1047,8 +1047,10 @@ bool __skb_flow_dissect(const struct net *net,
FLOW_DISSECTOR_KEY_IPV4_ADDRS,
target_container);

- memcpy(&key_addrs->v4addrs, &iph->saddr,
- sizeof(key_addrs->v4addrs));
+ memcpy(&key_addrs->v4addrs.src, &iph->saddr,
+ sizeof(key_addrs->v4addrs.src));
+ memcpy(&key_addrs->v4addrs.dst, &iph->daddr,
+ sizeof(key_addrs->v4addrs.dst));
key_control->addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
}

@@ -1092,8 +1094,10 @@ bool __skb_flow_dissect(const struct net *net,
FLOW_DISSECTOR_KEY_IPV6_ADDRS,
target_container);

- memcpy(&key_addrs->v6addrs, &iph->saddr,
- sizeof(key_addrs->v6addrs));
+ memcpy(&key_addrs->v6addrs.src, &iph->saddr,
+ sizeof(key_addrs->v6addrs.src));
+ memcpy(&key_addrs->v6addrs.dst, &iph->daddr,
+ sizeof(key_addrs->v6addrs.dst));
key_control->addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
}

--
2.30.2