From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Potapenko Subject: [PATCH] net/packet: check length in getsockopt() called with PACKET_HDRLEN Date: Tue, 25 Apr 2017 18:51:46 +0200 Message-ID: <20170425165146.25075-1-glider@google.com> Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: dvyukov@google.com, kcc@google.com, edumazet@google.com, davem@davemloft.net, kuznet@ms2.inr.ac.ru Return-path: Received: from mail-wm0-f53.google.com ([74.125.82.53]:35045 "EHLO mail-wm0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1432235AbdDYQwC (ORCPT ); Tue, 25 Apr 2017 12:52:02 -0400 Received: by mail-wm0-f53.google.com with SMTP id w64so28267756wma.0 for ; Tue, 25 Apr 2017 09:51:51 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: In the case getsockopt() is called with PACKET_HDRLEN and optlen < 4 |val| remains uninitialized and the syscall may behave differently depending on its value, and even copy garbage to userspace on certain architectures. To fix this we now return -EINVAL if optlen is too small. This bug has been detected with KMSAN. Signed-off-by: Alexander Potapenko --- The previous versions of this patch were called "net/packet: initialize val in packet_getsockopt()" v3: - change patch summary, return -EINVAL for optlen < sizeof(int) v2: - if len < sizeof(int), make it 0 --- net/packet/af_packet.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 8489beff5c25..ea81ccf3c7d6 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3836,6 +3836,8 @@ static int packet_getsockopt(struct socket *sock, int level, int optname, case PACKET_HDRLEN: if (len > sizeof(int)) len = sizeof(int); + if (len < sizeof(int)) + return -EINVAL; if (copy_from_user(&val, optval, len)) return -EFAULT; switch (val) { -- 2.13.0.rc0.306.g87b477812d-goog