Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753520Ab3FYSjy (ORCPT ); Tue, 25 Jun 2013 14:39:54 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:41409 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753497Ab3FYSjr (ORCPT ); Tue, 25 Jun 2013 14:39:47 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "David S. Miller" , Andy Lutomirski Subject: [ 10/17] net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg Date: Tue, 25 Jun 2013 11:39:25 -0700 Message-Id: <20130625183916.605109568@linuxfoundation.org> X-Mailer: git-send-email 1.8.3.rc0.20.gb99dd2e In-Reply-To: <20130625183915.443950649@linuxfoundation.org> References: <20130625183915.443950649@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8634 Lines: 273 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski [ Upstream commits 1be374a0518a288147c6a7398792583200a67261 and a7526eb5d06b0084ef12d7b168d008fcf516caab ] 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 Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/linux/socket.h | 3 ++ net/compat.c | 13 ++++++++- net/socket.c | 67 ++++++++++++++++++++++++++++++++----------------- 3 files changed, 59 insertions(+), 24 deletions(-) --- a/include/linux/socket.h +++ b/include/linux/socket.h @@ -332,6 +332,9 @@ extern int put_cmsg(struct msghdr*, int struct timespec; +/* The __sys_...msg variants allow MSG_CMSG_COMPAT */ +extern long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags); +extern long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags); extern int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen, unsigned int flags, struct timespec *timeout); extern int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, --- a/net/compat.c +++ b/net/compat.c @@ -732,19 +732,25 @@ static unsigned char nas[21] = { asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned flags) { - return sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT); + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + return __sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT); } asmlinkage long compat_sys_sendmmsg(int fd, struct compat_mmsghdr __user *mmsg, unsigned vlen, unsigned int flags) { + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; return __sys_sendmmsg(fd, (struct mmsghdr __user *)mmsg, vlen, flags | MSG_CMSG_COMPAT); } asmlinkage long compat_sys_recvmsg(int fd, struct compat_msghdr __user *msg, unsigned int flags) { - return sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT); + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + return __sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT); } asmlinkage long compat_sys_recv(int fd, void __user *buf, size_t len, unsigned flags) @@ -766,6 +772,9 @@ asmlinkage long compat_sys_recvmmsg(int int datagrams; struct timespec ktspec; + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + if (timeout == NULL) return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen, flags | MSG_CMSG_COMPAT, NULL); --- a/net/socket.c +++ b/net/socket.c @@ -1876,9 +1876,9 @@ struct used_address { unsigned int name_len; }; -static int __sys_sendmsg(struct socket *sock, struct msghdr __user *msg, - struct msghdr *msg_sys, unsigned flags, - struct used_address *used_address) +static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg, + struct msghdr *msg_sys, unsigned flags, + struct used_address *used_address) { struct compat_msghdr __user *msg_compat = (struct compat_msghdr __user *)msg; @@ -1998,22 +1998,30 @@ out: * BSD sendmsg interface */ -SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned, flags) +long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags) { int fput_needed, err; struct msghdr msg_sys; - struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed); + struct socket *sock; + sock = sockfd_lookup_light(fd, &err, &fput_needed); if (!sock) goto out; - err = __sys_sendmsg(sock, msg, &msg_sys, flags, NULL); + err = ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL); fput_light(sock->file, fput_needed); out: return err; } +SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags) +{ + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + return __sys_sendmsg(fd, msg, flags); +} + /* * Linux sendmmsg interface */ @@ -2044,15 +2052,16 @@ int __sys_sendmmsg(int fd, struct mmsghd while (datagrams < vlen) { if (MSG_CMSG_COMPAT & flags) { - err = __sys_sendmsg(sock, (struct msghdr __user *)compat_entry, - &msg_sys, flags, &used_address); + err = ___sys_sendmsg(sock, (struct msghdr __user *)compat_entry, + &msg_sys, flags, &used_address); if (err < 0) break; err = __put_user(err, &compat_entry->msg_len); ++compat_entry; } else { - err = __sys_sendmsg(sock, (struct msghdr __user *)entry, - &msg_sys, flags, &used_address); + err = ___sys_sendmsg(sock, + (struct msghdr __user *)entry, + &msg_sys, flags, &used_address); if (err < 0) break; err = put_user(err, &entry->msg_len); @@ -2076,11 +2085,13 @@ int __sys_sendmmsg(int fd, struct mmsghd 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); } -static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg, - struct msghdr *msg_sys, unsigned flags, int nosec) +static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg, + struct msghdr *msg_sys, unsigned flags, int nosec) { struct compat_msghdr __user *msg_compat = (struct compat_msghdr __user *)msg; @@ -2177,23 +2188,31 @@ out: * BSD recvmsg interface */ -SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg, - unsigned int, flags) +long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags) { int fput_needed, err; struct msghdr msg_sys; - struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed); + struct socket *sock; + sock = sockfd_lookup_light(fd, &err, &fput_needed); if (!sock) goto out; - err = __sys_recvmsg(sock, msg, &msg_sys, flags, 0); + err = ___sys_recvmsg(sock, msg, &msg_sys, flags, 0); fput_light(sock->file, fput_needed); out: return err; } +SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg, + unsigned int, flags) +{ + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + return __sys_recvmsg(fd, msg, flags); +} + /* * Linux recvmmsg interface */ @@ -2231,17 +2250,18 @@ int __sys_recvmmsg(int fd, struct mmsghd * No need to ask LSM for more than the first datagram. */ if (MSG_CMSG_COMPAT & flags) { - err = __sys_recvmsg(sock, (struct msghdr __user *)compat_entry, - &msg_sys, flags & ~MSG_WAITFORONE, - datagrams); + err = ___sys_recvmsg(sock, (struct msghdr __user *)compat_entry, + &msg_sys, flags & ~MSG_WAITFORONE, + datagrams); if (err < 0) break; err = __put_user(err, &compat_entry->msg_len); ++compat_entry; } else { - err = __sys_recvmsg(sock, (struct msghdr __user *)entry, - &msg_sys, flags & ~MSG_WAITFORONE, - datagrams); + err = ___sys_recvmsg(sock, + (struct msghdr __user *)entry, + &msg_sys, flags & ~MSG_WAITFORONE, + datagrams); if (err < 0) break; err = put_user(err, &entry->msg_len); @@ -2308,6 +2328,9 @@ SYSCALL_DEFINE5(recvmmsg, int, fd, struc int datagrams; struct timespec timeout_sys; + if (flags & MSG_CMSG_COMPAT) + return -EINVAL; + if (!timeout) return __sys_recvmmsg(fd, mmsg, vlen, flags, NULL); 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