From af323eb7c1830053627de6161f8ce73ac5f06d4e Mon Sep 17 00:00:00 2001
From: Ting-Yu Wang <anivia@google.com>
Date: Thu, 14 Nov 2019 17:02:59 -0800
Subject: Fix return codes for {get,set}sockopt for some nullptr cases.

Updates #1092

PiperOrigin-RevId: 280547239
---
 pkg/sentry/syscalls/linux/sys_socket.go  | 23 +++++++++--------------
 test/syscalls/linux/socket_ip_unbound.cc | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 14 deletions(-)

diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index b5a72ce63..ab1001f16 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -447,16 +447,13 @@ func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 		return 0, nil, syserror.ENOTSOCK
 	}
 
-	// Read the length if present. Reject negative values.
+	// Read the length. Reject negative values.
 	optLen := int32(0)
-	if optLenAddr != 0 {
-		if _, err := t.CopyIn(optLenAddr, &optLen); err != nil {
-			return 0, nil, err
-		}
-
-		if optLen < 0 {
-			return 0, nil, syserror.EINVAL
-		}
+	if _, err := t.CopyIn(optLenAddr, &optLen); err != nil {
+		return 0, nil, err
+	}
+	if optLen < 0 {
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Call syscall implementation then copy both value and value len out.
@@ -465,11 +462,9 @@ func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 		return 0, nil, e.ToError()
 	}
 
-	if optLenAddr != 0 {
-		vLen := int32(binary.Size(v))
-		if _, err := t.CopyOut(optLenAddr, vLen); err != nil {
-			return 0, nil, err
-		}
+	vLen := int32(binary.Size(v))
+	if _, err := t.CopyOut(optLenAddr, vLen); err != nil {
+		return 0, nil, err
 	}
 
 	if v != nil {
diff --git a/test/syscalls/linux/socket_ip_unbound.cc b/test/syscalls/linux/socket_ip_unbound.cc
index b02872308..b6754111f 100644
--- a/test/syscalls/linux/socket_ip_unbound.cc
+++ b/test/syscalls/linux/socket_ip_unbound.cc
@@ -354,6 +354,38 @@ TEST_P(IPUnboundSocketTest, InvalidNegativeTOS) {
   EXPECT_EQ(get, expect);
 }
 
+TEST_P(IPUnboundSocketTest, NullTOS) {
+  auto socket = ASSERT_NO_ERRNO_AND_VALUE(NewSocket());
+  TOSOption t = GetTOSOption(GetParam().domain);
+  int set_sz = sizeof(int);
+  if (GetParam().domain == AF_INET) {
+    EXPECT_THAT(setsockopt(socket->get(), t.level, t.option, nullptr, set_sz),
+                SyscallFailsWithErrno(EFAULT));
+  } else {  // AF_INET6
+    // The AF_INET6 behavior is not yet compatible. gVisor will try to read
+    // optval from user memory at syscall handler, it needs substantial
+    // refactoring to implement this behavior just for IPv6.
+    if (IsRunningOnGvisor()) {
+      EXPECT_THAT(setsockopt(socket->get(), t.level, t.option, nullptr, set_sz),
+                  SyscallFailsWithErrno(EFAULT));
+    } else {
+      // Linux's IPv6 stack treats nullptr optval as input of 0, so the call
+      // succeeds. (net/ipv6/ipv6_sockglue.c, do_ipv6_setsockopt())
+      //
+      // Linux's implementation would need fixing as passing a nullptr as optval
+      // and non-zero optlen may not be valid.
+      EXPECT_THAT(setsockopt(socket->get(), t.level, t.option, nullptr, set_sz),
+                  SyscallSucceedsWithValue(0));
+    }
+  }
+  socklen_t get_sz = sizeof(int);
+  EXPECT_THAT(getsockopt(socket->get(), t.level, t.option, nullptr, &get_sz),
+              SyscallFailsWithErrno(EFAULT));
+  int get = -1;
+  EXPECT_THAT(getsockopt(socket->get(), t.level, t.option, &get, nullptr),
+              SyscallFailsWithErrno(EFAULT));
+}
+
 INSTANTIATE_TEST_SUITE_P(
     IPUnboundSockets, IPUnboundSocketTest,
     ::testing::ValuesIn(VecCat<SocketKind>(VecCat<SocketKind>(
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