From: "GONG, Ruiqi" <gongruiqi@huaweicloud.com>
To: Pablo Neira Ayuso <pablo@netfilter.org>,
Jozsef Kadlecsik <kadlec@netfilter.org>,
Florian Westphal <fw@strlen.de>, Roopa Prabhu <roopa@nvidia.com>,
Nikolay Aleksandrov <razor@blackwall.org>,
"David S . Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: Kees Cook <keescook@chromium.org>,
netdev@vger.kernel.org, bridge@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
"Gustavo A . R . Silva" <gustavoars@kernel.org>,
coreteam@netfilter.org, netfilter-devel@vger.kernel.org,
gongruiqi1@huawei.com
Subject: [Bridge] [PATCH net-next v4] netfilter: ebtables: fix fortify warnings in size_entry_mwt()
Date: Wed, 16 Aug 2023 09:54:46 -0000 [thread overview]
Message-ID: <20230816093248.1459951-1-gongruiqi@huaweicloud.com> (raw)
From: "GONG, Ruiqi" <gongruiqi1@huawei.com>
When compiling with gcc 13 and CONFIG_FORTIFY_SOURCE=y, the following
warning appears:
In function ‘fortify_memcpy_chk’,
inlined from ‘size_entry_mwt’ at net/bridge/netfilter/ebtables.c:2118:2:
./include/linux/fortify-string.h:592:25: error: call to ‘__read_overflow2_field’
declared with attribute warning: detected read beyond size of field (2nd parameter);
maybe use struct_group()? [-Werror=attribute-warning]
592 | __read_overflow2_field(q_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The compiler is complaining:
memcpy(&offsets[1], &entry->watchers_offset,
sizeof(offsets) - sizeof(offsets[0]));
where memcpy reads beyond &entry->watchers_offset to copy
{watchers,target,next}_offset altogether into offsets[]. Silence the
warning by wrapping these three up via struct_group().
Signed-off-by: GONG, Ruiqi <gongruiqi1@huawei.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
v4: fix a typo in commit msg; designate to net-next; cc more netdev
maintainers.
v3: use sizeof(entry->offsets) as memcpy()'s size, as Gustavo suggested.
v2: fix HDRTEST error by replacing struct_group() with __struct_group(),
since it's a uapi header.
include/uapi/linux/netfilter_bridge/ebtables.h | 14 ++++++++------
net/bridge/netfilter/ebtables.c | 3 +--
2 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/include/uapi/linux/netfilter_bridge/ebtables.h b/include/uapi/linux/netfilter_bridge/ebtables.h
index a494cf43a755..b0caad82b693 100644
--- a/include/uapi/linux/netfilter_bridge/ebtables.h
+++ b/include/uapi/linux/netfilter_bridge/ebtables.h
@@ -182,12 +182,14 @@ struct ebt_entry {
unsigned char sourcemsk[ETH_ALEN];
unsigned char destmac[ETH_ALEN];
unsigned char destmsk[ETH_ALEN];
- /* sizeof ebt_entry + matches */
- unsigned int watchers_offset;
- /* sizeof ebt_entry + matches + watchers */
- unsigned int target_offset;
- /* sizeof ebt_entry + matches + watchers + target */
- unsigned int next_offset;
+ __struct_group(/* no tag */, offsets, /* no attrs */,
+ /* sizeof ebt_entry + matches */
+ unsigned int watchers_offset;
+ /* sizeof ebt_entry + matches + watchers */
+ unsigned int target_offset;
+ /* sizeof ebt_entry + matches + watchers + target */
+ unsigned int next_offset;
+ );
unsigned char elems[0] __attribute__ ((aligned (__alignof__(struct ebt_replace))));
};
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 757ec46fc45a..aa23479b20b2 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2115,8 +2115,7 @@ static int size_entry_mwt(const struct ebt_entry *entry, const unsigned char *ba
return ret;
offsets[0] = sizeof(struct ebt_entry); /* matches come first */
- memcpy(&offsets[1], &entry->watchers_offset,
- sizeof(offsets) - sizeof(offsets[0]));
+ memcpy(&offsets[1], &entry->offsets, sizeof(entry->offsets));
if (state->buf_kern_start) {
buf_start = state->buf_kern_start + state->buf_kern_offset;
--
2.41.0
reply other threads:[~2023-08-16 9:54 UTC|newest]
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