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authorAndy Lutomirski <luto@amacapital.net>2013-05-22 14:07:44 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-06-27 11:27:32 -0700
commitc0cc94f2f65a682827cca2a79a4d045a20f8897f (patch)
tree5f5ec066b0c72524ccd349861b17666dd49a06e1 /include
parent3c353df4ca0f8f6912e103ca6d8d593ff4563b68 (diff)
net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg
[ 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; } Signed-off-by: Andy Lutomirski <luto@amacapital.net> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/socket.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 8f15b1d0031e..9b54ebef1739 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -336,6 +336,9 @@ extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
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,