From: Kees Cook <keescook@chromium•org>
To: Jakub Kicinski <kuba@kernel•org>
Cc: Kees Cook <keescook@chromium•org>,
"David S. Miller" <davem@davemloft•net>,
Eric Dumazet <edumazet@google•com>,
Paolo Abeni <pabeni@redhat•com>,
netdev@vger•kernel.org, Kuniyuki Iwashima <kuniyu@amazon•com>,
Abel Wu <wuyun.abel@bytedance•com>,
Breno Leitao <leitao@debian•org>,
Alexander Mikhalitsyn <alexander@mihalicyn•com>,
David Howells <dhowells@redhat•com>,
linux-kernel@vger•kernel.org, linux-hardening@vger•kernel.org
Subject: [PATCH] sock: Use unsafe_memcpy() for sock_copy()
Date: Fri, 16 Feb 2024 12:44:24 -0800 [thread overview]
Message-ID: <20240216204423.work.066-kees@kernel.org> (raw)
While testing for places where zero-sized destinations were still
showing up in the kernel, sock_copy() was found, which is using very
specific memcpy() offsets for both avoiding a portion of struct sock,
and copying beyond the end of it (since struct sock is really just a
common header before the protocol-specific allocation). Instead of
trying to unravel this historical lack of container_of(), just switch
to unsafe_memcpy(), since that's effectively what was happening already
(memcpy() wasn't checking 0-sized destinations while the code base was
being converted away from fake flexible arrays).
Avoid the following false positive warning with future changes to
CONFIG_FORTIFY_SOURCE:
memcpy: detected field-spanning write (size 3068) of destination "&nsk->__sk_common.skc_dontcopy_end" at net/core/sock.c:2057 (size 0)
Signed-off-by: Kees Cook <keescook@chromium•org>
---
Cc: Jakub Kicinski <kuba@kernel•org>
Cc: "David S. Miller" <davem@davemloft•net>
Cc: Eric Dumazet <edumazet@google•com>
Cc: Paolo Abeni <pabeni@redhat•com>
Cc: netdev@vger•kernel.org
---
net/core/sock.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index 0a7f46c37f0c..b7ea358eb18f 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2053,8 +2053,9 @@ static void sock_copy(struct sock *nsk, const struct sock *osk)
memcpy(nsk, osk, offsetof(struct sock, sk_dontcopy_begin));
- memcpy(&nsk->sk_dontcopy_end, &osk->sk_dontcopy_end,
- prot->obj_size - offsetof(struct sock, sk_dontcopy_end));
+ unsafe_memcpy(&nsk->sk_dontcopy_end, &osk->sk_dontcopy_end,
+ prot->obj_size - offsetof(struct sock, sk_dontcopy_end),
+ /* alloc is larger than struct, see sk_prot_alloc() */);
#ifdef CONFIG_SECURITY_NETWORK
nsk->sk_security = sptr;
--
2.34.1
next reply other threads:[~2024-02-16 20:44 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-16 20:44 Kees Cook [this message]
2024-02-16 22:06 ` [PATCH] sock: Use unsafe_memcpy() for sock_copy() Kuniyuki Iwashima
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