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authorAndy Lutomirski <luto@amacapital.net>2013-05-22 14:07:44 -0700
committerDavid S. Miller <davem@davemloft.net>2013-05-28 23:55:41 -0700
commit1be374a0518a288147c6a7398792583200a67261 (patch)
tree83f0bbaa40655d1af02dc761b594f46958354a00 /net/socket.c
parentf96ef988cc603487c03a6de07807b06cbe641829 (diff)
downloadlinux-1be374a0518a288147c6a7398792583200a67261.tar.gz
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 <luto@amacapital.net>, netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net> 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 <davem@davemloft.net> Signed-off-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/socket.c')
-rw-r--r--net/socket.c33
1 files changed, 31 insertions, 2 deletions
diff --git a/net/socket.c b/net/socket.c
index 6b94633ca61..9ff6366fee1 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;