From 42467f5b7bf4eef20f78f796fc6eb10401784d86 Mon Sep 17 00:00:00 2001
From: Dmitry Vyukov <dvyukov@google.com>
Date: Mon, 5 Mar 2018 12:07:59 +0100
Subject: sys/linux: add syz_init_net_socket syscall

The new pseudo syscall allows opening sockets that can only
be created in init net namespace (BLUETOOTH, NFC, LLC).
Use it to open these sockets.

Unfortunately this only works with sandbox none at the moment.
The problem is that setns of a network namespace requires CAP_SYS_ADMIN
in the target namespace, and we've lost all privs in the init namespace
during creation of a user namespace.
---
 executor/common_linux.h | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

(limited to 'executor/common_linux.h')

diff --git a/executor/common_linux.h b/executor/common_linux.h
index 1f8305bce..414b80f37 100644
--- a/executor/common_linux.h
+++ b/executor/common_linux.h
@@ -112,11 +112,19 @@
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 #endif
+#if defined(SYZ_EXECUTOR) || defined(__NR_syz_init_net_socket)
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#endif
 
 #if defined(SYZ_EXECUTOR) || (defined(SYZ_REPEAT) && defined(SYZ_WAIT_REPEAT)) ||      \
     defined(SYZ_USE_TMP_DIR) || defined(SYZ_HANDLE_SEGV) || defined(SYZ_TUN_ENABLE) || \
     defined(SYZ_SANDBOX_NAMESPACE) || defined(SYZ_SANDBOX_SETUID) ||                   \
-    defined(SYZ_SANDBOX_NONE) || defined(SYZ_FAULT_INJECTION) || defined(__NR_syz_kvm_setup_cpu)
+    defined(SYZ_SANDBOX_NONE) || defined(SYZ_FAULT_INJECTION) ||                       \
+    defined(__NR_syz_kvm_setup_cpu) || defined(__NR_syz_init_net_socket)
 // One does not simply exit.
 // _exit can in fact fail.
 // syzkaller did manage to generate a seccomp filter that prohibits exit_group syscall.
@@ -688,6 +696,34 @@ static uintptr_t syz_fuseblk_mount(uintptr_t a0, uintptr_t a1, uintptr_t a2, uin
 }
 #endif
 
+#if defined(SYZ_EXECUTOR) || defined(__NR_syz_init_net_socket)
+#if defined(SYZ_EXECUTOR) || defined(SYZ_SANDBOX_NONE) || defined(SYZ_SANDBOX_SETUID) || defined(SYZ_SANDBOX_NAMESPACE)
+const int kInitNetNsFd = 253;
+// syz_init_net_socket opens a socket in init net namespace.
+// Used for families that can only be created in init net namespace.
+static uintptr_t syz_init_net_socket(uintptr_t domain, uintptr_t type, uintptr_t proto)
+{
+	int netns = open("/proc/self/ns/net", O_RDONLY);
+	if (netns == -1)
+		return netns;
+	if (setns(kInitNetNsFd, 0))
+		return -1;
+	int sock = syscall(__NR_socket, domain, type, proto);
+	int err = errno;
+	if (setns(netns, 0))
+		fail("setns(netns) failed");
+	close(netns);
+	errno = err;
+	return sock;
+}
+#else
+static uintptr_t syz_init_net_socket(uintptr_t domain, uintptr_t type, uintptr_t proto)
+{
+	return syscall(__NR_socket, domain, type, proto);
+}
+#endif
+#endif
+
 #if defined(SYZ_EXECUTOR) || defined(__NR_syz_kvm_setup_cpu)
 #if defined(__x86_64__)
 #include "common_kvm_amd64.h"
@@ -710,6 +746,15 @@ static void sandbox_common()
 	setpgrp();
 	setsid();
 
+#if defined(SYZ_EXECUTOR) || defined(__NR_syz_init_net_socket)
+	int netns = open("/proc/self/ns/net", O_RDONLY);
+	if (netns == -1)
+		fail("open(/proc/self/ns/net) failed");
+	if (dup2(netns, kInitNetNsFd) < 0)
+		fail("dup2(netns, kInitNetNsFd) failed");
+	close(netns);
+#endif
+
 	struct rlimit rlim;
 	rlim.rlim_cur = rlim.rlim_max = 128 << 20;
 	setrlimit(RLIMIT_AS, &rlim);
-- 
cgit mrf-deployment