Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757454Ab3EVVJE (ORCPT ); Wed, 22 May 2013 17:09:04 -0400 Received: from mail-pb0-f48.google.com ([209.85.160.48]:44212 "EHLO mail-pb0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757412Ab3EVVIY (ORCPT ); Wed, 22 May 2013 17:08:24 -0400 From: Andy Lutomirski To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, trinity@vger.kernel.org, Andy Lutomirski , netdev@vger.kernel.org, "David S. Miller" Subject: [PATCH 5/5] net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg Date: Wed, 22 May 2013 14:07:44 -0700 Message-Id: X-Mailer: git-send-email 1.8.1.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3751 Lines: 135 MSG_CMSG_COMPAT is (AFAIK) not intended to be part of the API -- it's a hack that steals a bit to indicate to other networking code that a compat entry was used. So don't allow it from a non-compat syscall. This prevents an oops when running this code: int main() { int s; struct sockaddr_in addr; struct msghdr *hdr; char *highpage = mmap((void*)(TASK_SIZE_MAX - 4096), 4096, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0); if (highpage == MAP_FAILED) err(1, "mmap"); s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); if (s == -1) err(1, "socket"); addr.sin_family = AF_INET; addr.sin_port = htons(1); addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK); if (connect(s, (struct sockaddr*)&addr, sizeof(addr)) != 0) err(1, "connect"); void *evil = highpage + 4096 - COMPAT_MSGHDR_SIZE; printf("Evil address is %p\n", evil); if (syscall(__NR_sendmmsg, s, evil, 1, MSG_CMSG_COMPAT) < 0) err(1, "sendmmsg"); return 0; } Cc: David S. Miller Signed-off-by: Andy Lutomirski --- net/socket.c | 33 +++++++++++++++++++++++++++++++-- 1 file changed, 31 insertions(+), 2 deletions(-) diff --git a/net/socket.c b/net/socket.c index 88f759a..0e16888 100644 --- a/net/socket.c +++ b/net/socket.c @@ -2097,8 +2097,12 @@ SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, fla { int fput_needed, err; struct msghdr msg_sys; - struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed); + struct socket *sock; + + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + sock = sockfd_lookup_light(fd, &err, &fput_needed); if (!sock) goto out; @@ -2171,6 +2175,8 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen, SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg, unsigned int, vlen, unsigned int, flags) { + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; return __sys_sendmmsg(fd, mmsg, vlen, flags); } @@ -2271,8 +2277,12 @@ SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg, { int fput_needed, err; struct msghdr msg_sys; - struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed); + struct socket *sock; + + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + sock = sockfd_lookup_light(fd, &err, &fput_needed); if (!sock) goto out; @@ -2397,6 +2407,9 @@ SYSCALL_DEFINE5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg, int datagrams; struct timespec timeout_sys; + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + if (!timeout) return __sys_recvmmsg(fd, mmsg, vlen, flags, NULL); @@ -2512,15 +2525,31 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args) (int __user *)a[4]); break; case SYS_SENDMSG: + if (a[2] & MSG_CMSG_COMPAT) { + err = -EINVAL; + break; + } err = sys_sendmsg(a0, (struct msghdr __user *)a1, a[2]); break; case SYS_SENDMMSG: + if (a[3] & MSG_CMSG_COMPAT) { + err = -EINVAL; + break; + } err = sys_sendmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3]); break; case SYS_RECVMSG: + if (a[2] & MSG_CMSG_COMPAT) { + err = -EINVAL; + break; + } err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]); break; case SYS_RECVMMSG: + if (a[3] & MSG_CMSG_COMPAT) { + err = -EINVAL; + break; + } err = sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3], (struct timespec __user *)a[4]); break; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/