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Message-Id: <20240216233128.work.366-kees@kernel.org>
Date: Fri, 16 Feb 2024 15:31:32 -0800
From: Kees Cook <keescook@...omium.org>
To: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Kees Cook <keescook@...omium.org>,
Jozsef Kadlecsik <kadlec@...filter.org>,
Florian Westphal <fw@...len.de>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
"Gustavo A . R . Silva" <gustavo@...eddedor.com>,
netfilter-devel@...r.kernel.org,
coreteam@...filter.org,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org
Subject: [PATCH] netfilter: x_tables: Use unsafe_memcpy() for 0-sized destination
The struct xt_entry_target fake flexible array has not be converted to a
true flexible array, which is mainly blocked by it being both UAPI and
used in the middle of other structures. In order to properly check for
0-sized destinations in memcpy(), an exception must be made for the one
place where it is still a destination. Since memcpy() was already
skipping checks for 0-sized destinations, using unsafe_memcpy() is no
change in behavior.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
Cc: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Jozsef Kadlecsik <kadlec@...filter.org>
Cc: Florian Westphal <fw@...len.de>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: Gustavo A. R. Silva <gustavo@...eddedor.com>
Cc: netfilter-devel@...r.kernel.org
Cc: coreteam@...filter.org
Cc: netdev@...r.kernel.org
---
net/netfilter/x_tables.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 21624d68314f..da5d929c7c85 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1142,7 +1142,8 @@ void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
if (target->compat_from_user)
target->compat_from_user(t->data, ct->data);
else
- memcpy(t->data, ct->data, tsize - sizeof(*ct));
+ unsafe_memcpy(t->data, ct->data, tsize - sizeof(*ct),
+ /* UAPI 0-sized destination */);
tsize += off;
t->u.user.target_size = tsize;
--
2.34.1
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