workaround another sendmsg kernel bug on 64-bit machines

the kernel wrongly expects the cmsg length field to be size_t instead
of socklen_t. in order to work around the issue, we have to impose a
length limit and copy to a local buffer. the length limit should be
more than sufficient for any real-world use; these headers are only
used for passing file descriptors and permissions between processes
over unix sockets.

4 files changed, 29 insertions, 0 deletions

diff --git a/arch/arm/bits/socket.h b/arch/arm/bits/socket.h
index c464ed90..36febbc2 100644
--- a/arch/arm/bits/socket.h
+++ b/arch/arm/bits/socket.h
@@ -8,3 +8,10 @@ struct msghdr
 	socklen_t msg_controllen;
 	int msg_flags;
 };
+
+struct cmsghdr
+{
+	socklen_t cmsg_len;
+	int cmsg_level;
+	int cmsg_type;
+};
diff --git a/arch/i386/bits/socket.h b/arch/i386/bits/socket.h
index c464ed90..36febbc2 100644
--- a/arch/i386/bits/socket.h
+++ b/arch/i386/bits/socket.h
@@ -8,3 +8,10 @@ struct msghdr
 	socklen_t msg_controllen;
 	int msg_flags;
 };
+
+struct cmsghdr
+{
+	socklen_t cmsg_len;
+	int cmsg_level;
+	int cmsg_type;
+};
diff --git a/arch/mips/bits/socket.h b/arch/mips/bits/socket.h
index c464ed90..36febbc2 100644
--- a/arch/mips/bits/socket.h
+++ b/arch/mips/bits/socket.h
@@ -8,3 +8,10 @@ struct msghdr
 	socklen_t msg_controllen;
 	int msg_flags;
 };
+
+struct cmsghdr
+{
+	socklen_t cmsg_len;
+	int cmsg_level;
+	int cmsg_type;
+};
diff --git a/arch/x86_64/bits/socket.h b/arch/x86_64/bits/socket.h
index 878ab117..a90c4cae 100644
--- a/arch/x86_64/bits/socket.h
+++ b/arch/x86_64/bits/socket.h
@@ -8,3 +8,11 @@ struct msghdr
 	socklen_t msg_controllen, __pad2;
 	int msg_flags;
 };
+
+struct cmsghdr
+{
+	socklen_t cmsg_len;
+	int __pad1;
+	int cmsg_level;
+	int cmsg_type;
+};