From 1be374a0518a288147c6a7398792583200a67261 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 22 May 2013 14:07:44 -0700 Subject: net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg 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 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 --- net/socket.c | 33 +++++++++++++++++++++++++++++++-- 1 file changed, 31 insertions(+), 2 deletions(-) (limited to 'net/socket.c') diff --git a/net/socket.c b/net/socket.c index 6b94633ca61d..9ff6366fee13 100644 --- a/net/socket.c +++ b/net/socket.c @@ -2075,8 +2075,12 @@ 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; @@ -2149,6 +2153,8 @@ 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); } @@ -2249,8 +2255,12 @@ 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; @@ -2375,6 +2385,9 @@ 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); @@ -2492,15 +2505,31 @@ 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; -- cgit v1.2.3 From a7526eb5d06b0084ef12d7b168d008fcf516caab Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 5 Jun 2013 19:38:26 +0000 Subject: net: Unbreak compat_sys_{send,recv}msg I broke them in this commit: commit 1be374a0518a288147c6a7398792583200a67261 Author: Andy Lutomirski Date: Wed May 22 14:07:44 2013 -0700 net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg This patch adds __sys_sendmsg and __sys_sendmsg as common helpers that accept MSG_CMSG_COMPAT and blocks MSG_CMSG_COMPAT at the syscall entrypoints. It also reverts some unnecessary checks in sys_socketcall. Apparently I was suffering from underscore blindness the first time around. Signed-off-by: Andy Lutomirski Tested-by: Eric Dumazet Signed-off-by: David S. Miller --- net/socket.c | 72 ++++++++++++++++++++++++++++-------------------------------- 1 file changed, 33 insertions(+), 39 deletions(-) (limited to 'net/socket.c') diff --git a/net/socket.c b/net/socket.c index 9ff6366fee13..4ca1526db756 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1956,7 +1956,7 @@ struct used_address { unsigned int name_len; }; -static int __sys_sendmsg(struct socket *sock, struct msghdr __user *msg, +static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg, struct msghdr *msg_sys, unsigned int flags, struct used_address *used_address) { @@ -2071,26 +2071,30 @@ out: * BSD sendmsg interface */ -SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags) +long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags) { int fput_needed, err; struct msghdr msg_sys; struct socket *sock; - if (flags & MSG_CMSG_COMPAT) - return -EINVAL; - 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 */ @@ -2121,15 +2125,16 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen, 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); @@ -2158,7 +2163,7 @@ SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg, return __sys_sendmmsg(fd, mmsg, vlen, flags); } -static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg, +static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg, struct msghdr *msg_sys, unsigned int flags, int nosec) { struct compat_msghdr __user *msg_compat = @@ -2250,27 +2255,31 @@ 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; - if (flags & MSG_CMSG_COMPAT) - return -EINVAL; - 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 */ @@ -2308,17 +2317,18 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen, * 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); @@ -2505,31 +2515,15 @@ 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; -- cgit v1.2.3