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Fix AF_UNIX listen() w/ zero backlog.

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In https://github.com/google/gvisor/commit/f075522849fa a check to increase zero
to a minimum backlog length was removed from sys_socket.go to bring it in parity
with linux and then in tcp/endpoint.go we bump backlog by 1. But this broke
calling listen on a AF_UNIX socket w/ a zero backlog as in linux it does allow 1
connection even with a zero backlog.

This was caught by a php runtime test socket_abstract_path.phpt.

PiperOrigin-RevId: 369974744
This commit is contained in:
Bhasker Hariharan
2021-04-22 16:34:00 -07:00
committed by gVisor bot
parent 0a6eaed50b
commit 2739cf4628
6 changed files with 71 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/sentry/socket/unix/transport/connectioned.go
+2 -2
View File
@@ -346,11 +346,11 @@ func (e *connectionedEndpoint) BidirectionalConnect(ctx context.Context, ce Conn
return nil
default:
// Busy; return ECONNREFUSED per spec.
// Busy; return EAGAIN per spec.
ne.Close(ctx)
e.Unlock()
ce.Unlock()
return syserr.ErrConnectionRefused
return syserr.ErrTryAgain
}
}
pkg/sentry/syscalls/linux/sys_socket.go
+10 -3
View File
@@ -383,12 +383,19 @@ func Listen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
// Linux treats incoming backlog as uint with a limit defined by
// sysctl_somaxconn.
// https://github.com/torvalds/linux/blob/7acac4b3196/net/socket.c#L1666
//
// We use the backlog to allocate a channel of that size, hence enforce
// a hard limit for the backlog.
backlog = maxListenBacklog
}
// Accept one more than the configured listen backlog to keep in parity with
// Linux. Ref, because of missing equality check here:
// https://github.com/torvalds/linux/blob/7acac4b3196/include/net/sock.h#L937
//
// In case of unix domain sockets, the following check
// https://github.com/torvalds/linux/blob/7d6beb71da3/net/unix/af_unix.c#L1293
// will allow 1 connect through since it checks for a receive queue len >
// backlog and not >=.
backlog++
return 0, nil, s.Listen(t, int(backlog)).ToError()
}
pkg/sentry/syscalls/linux/vfs2/socket.go
+10 -3
View File
@@ -387,12 +387,19 @@ func Listen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
// Linux treats incoming backlog as uint with a limit defined by
// sysctl_somaxconn.
// https://github.com/torvalds/linux/blob/7acac4b3196/net/socket.c#L1666
//
// We use the backlog to allocate a channel of that size, hence enforce
// a hard limit for the backlog.
backlog = maxListenBacklog
}
// Accept one more than the configured listen backlog to keep in parity with
// Linux. Ref, because of missing equality check here:
// https://github.com/torvalds/linux/blob/7acac4b3196/include/net/sock.h#L937
//
// In case of unix domain sockets, the following check
// https://github.com/torvalds/linux/blob/7d6beb71da3/net/unix/af_unix.c#L1293
// will allow 1 connect through since it checks for a receive queue len >
// backlog and not >=.
backlog++
return 0, nil, s.Listen(t, int(backlog)).ToError()
}
pkg/tcpip/transport/tcp/endpoint.go
-4
View File
@@ -2398,10 +2398,6 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) tcpip.Error {
// Listen puts the endpoint in "listen" mode, which allows it to accept
// new connections.
func (e *endpoint) Listen(backlog int) tcpip.Error {
// Accept one more than the configured listen backlog to keep in parity with
// Linux. Ref, because of missing equality check here:
// https://github.com/torvalds/linux/blob/7acac4b3196/include/net/sock.h#L937
backlog++
err := e.listen(backlog)
if err != nil {
if !err.IgnoreStats() {
pkg/tcpip/transport/tcp/tcp_test.go
+3 -3
View File
@@ -5736,7 +5736,7 @@ func TestListenSynRcvdQueueFull(t *testing.T) {
}
// Test acceptance.
if err := c.EP.Listen(0); err != nil {
if err := c.EP.Listen(1); err != nil {
t.Fatalf("Listen failed: %s", err)
}
@@ -5837,7 +5837,7 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
}
// Test for SynCookies usage after filling up the backlog.
if err := c.EP.Listen(0); err != nil {
if err := c.EP.Listen(1); err != nil {
t.Fatalf("Listen failed: %s", err)
}
@@ -6120,7 +6120,7 @@ func TestPassiveFailedConnectionAttemptIncrement(t *testing.T) {
if err := c.EP.Bind(tcpip.FullAddress{Addr: context.StackAddr, Port: context.StackPort}); err != nil {
t.Fatalf("Bind failed: %s", err)
}
if err := c.EP.Listen(0); err != nil {
if err := c.EP.Listen(1); err != nil {
t.Fatalf("Listen failed: %s", err)
}
test/syscalls/linux/socket_unix_unbound_abstract.cc
+46
View File
@@ -72,6 +72,52 @@ TEST_P(UnboundAbstractUnixSocketPairTest, BindNothing) {
SyscallSucceeds());
}
TEST_P(UnboundAbstractUnixSocketPairTest, ListenZeroBacklog) {
SKIP_IF((GetParam().type & SOCK_DGRAM) != 0);
auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
struct sockaddr_un addr = {};
addr.sun_family = AF_UNIX;
constexpr char kPath[] = "\x00/foo_bar";
memcpy(addr.sun_path, kPath, sizeof(kPath));
ASSERT_THAT(bind(sockets->first_fd(),
reinterpret_cast<struct sockaddr*>(&addr), sizeof(addr)),
SyscallSucceeds());
ASSERT_THAT(listen(sockets->first_fd(), 0 /* backlog */), SyscallSucceeds());
ASSERT_THAT(connect(sockets->second_fd(),
reinterpret_cast<struct sockaddr*>(&addr), sizeof(addr)),
SyscallSucceeds());
auto sockets2 = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
{
// Set the FD to O_NONBLOCK.
int opts;
int orig_opts;
ASSERT_THAT(opts = fcntl(sockets2->first_fd(), F_GETFL), SyscallSucceeds());
orig_opts = opts;
opts |= O_NONBLOCK;
ASSERT_THAT(fcntl(sockets2->first_fd(), F_SETFL, opts), SyscallSucceeds());
ASSERT_THAT(
connect(sockets2->first_fd(), reinterpret_cast<struct sockaddr*>(&addr),
sizeof(addr)),
SyscallFailsWithErrno(EAGAIN));
}
{
// Set the FD to O_NONBLOCK.
int opts;
int orig_opts;
ASSERT_THAT(opts = fcntl(sockets2->second_fd(), F_GETFL),
SyscallSucceeds());
orig_opts = opts;
opts |= O_NONBLOCK;
ASSERT_THAT(fcntl(sockets2->second_fd(), F_SETFL, opts), SyscallSucceeds());
ASSERT_THAT(
connect(sockets2->second_fd(),
reinterpret_cast<struct sockaddr*>(&addr), sizeof(addr)),
SyscallFailsWithErrno(EAGAIN));
}
}
TEST_P(UnboundAbstractUnixSocketPairTest, GetSockNameFullLength) {
auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());