mirror of https://go.googlesource.com/go
738 lines
23 KiB
Go
738 lines
23 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build linux
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package syscall
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import (
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"internal/itoa"
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"runtime"
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"unsafe"
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)
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// Linux unshare/clone/clone2/clone3 flags, architecture-independent,
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// copied from linux/sched.h.
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const (
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CLONE_VM = 0x00000100 // set if VM shared between processes
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CLONE_FS = 0x00000200 // set if fs info shared between processes
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CLONE_FILES = 0x00000400 // set if open files shared between processes
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CLONE_SIGHAND = 0x00000800 // set if signal handlers and blocked signals shared
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CLONE_PIDFD = 0x00001000 // set if a pidfd should be placed in parent
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CLONE_PTRACE = 0x00002000 // set if we want to let tracing continue on the child too
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CLONE_VFORK = 0x00004000 // set if the parent wants the child to wake it up on mm_release
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CLONE_PARENT = 0x00008000 // set if we want to have the same parent as the cloner
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CLONE_THREAD = 0x00010000 // Same thread group?
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CLONE_NEWNS = 0x00020000 // New mount namespace group
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CLONE_SYSVSEM = 0x00040000 // share system V SEM_UNDO semantics
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CLONE_SETTLS = 0x00080000 // create a new TLS for the child
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CLONE_PARENT_SETTID = 0x00100000 // set the TID in the parent
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CLONE_CHILD_CLEARTID = 0x00200000 // clear the TID in the child
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CLONE_DETACHED = 0x00400000 // Unused, ignored
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CLONE_UNTRACED = 0x00800000 // set if the tracing process can't force CLONE_PTRACE on this clone
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CLONE_CHILD_SETTID = 0x01000000 // set the TID in the child
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CLONE_NEWCGROUP = 0x02000000 // New cgroup namespace
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CLONE_NEWUTS = 0x04000000 // New utsname namespace
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CLONE_NEWIPC = 0x08000000 // New ipc namespace
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CLONE_NEWUSER = 0x10000000 // New user namespace
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CLONE_NEWPID = 0x20000000 // New pid namespace
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CLONE_NEWNET = 0x40000000 // New network namespace
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CLONE_IO = 0x80000000 // Clone io context
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// Flags for the clone3() syscall.
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CLONE_CLEAR_SIGHAND = 0x100000000 // Clear any signal handler and reset to SIG_DFL.
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CLONE_INTO_CGROUP = 0x200000000 // Clone into a specific cgroup given the right permissions.
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// Cloning flags intersect with CSIGNAL so can be used with unshare and clone3
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// syscalls only:
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CLONE_NEWTIME = 0x00000080 // New time namespace
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)
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// SysProcIDMap holds Container ID to Host ID mappings used for User Namespaces in Linux.
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// See user_namespaces(7).
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//
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// Note that User Namespaces are not available on a number of popular Linux
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// versions (due to security issues), or are available but subject to AppArmor
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// restrictions like in Ubuntu 24.04.
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type SysProcIDMap struct {
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ContainerID int // Container ID.
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HostID int // Host ID.
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Size int // Size.
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}
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type SysProcAttr struct {
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Chroot string // Chroot.
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Credential *Credential // Credential.
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// Ptrace tells the child to call ptrace(PTRACE_TRACEME).
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// Call runtime.LockOSThread before starting a process with this set,
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// and don't call UnlockOSThread until done with PtraceSyscall calls.
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Ptrace bool
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Setsid bool // Create session.
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// Setpgid sets the process group ID of the child to Pgid,
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// or, if Pgid == 0, to the new child's process ID.
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Setpgid bool
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// Setctty sets the controlling terminal of the child to
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// file descriptor Ctty. Ctty must be a descriptor number
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// in the child process: an index into ProcAttr.Files.
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// This is only meaningful if Setsid is true.
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Setctty bool
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Noctty bool // Detach fd 0 from controlling terminal.
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Ctty int // Controlling TTY fd.
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// Foreground places the child process group in the foreground.
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// This implies Setpgid. The Ctty field must be set to
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// the descriptor of the controlling TTY.
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// Unlike Setctty, in this case Ctty must be a descriptor
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// number in the parent process.
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Foreground bool
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Pgid int // Child's process group ID if Setpgid.
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// Pdeathsig, if non-zero, is a signal that the kernel will send to
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// the child process when the creating thread dies. Note that the signal
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// is sent on thread termination, which may happen before process termination.
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// There are more details at https://go.dev/issue/27505.
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Pdeathsig Signal
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Cloneflags uintptr // Flags for clone calls.
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Unshareflags uintptr // Flags for unshare calls.
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UidMappings []SysProcIDMap // User ID mappings for user namespaces.
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GidMappings []SysProcIDMap // Group ID mappings for user namespaces.
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// GidMappingsEnableSetgroups enabling setgroups syscall.
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// If false, then setgroups syscall will be disabled for the child process.
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// This parameter is no-op if GidMappings == nil. Otherwise for unprivileged
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// users this should be set to false for mappings work.
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GidMappingsEnableSetgroups bool
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AmbientCaps []uintptr // Ambient capabilities.
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UseCgroupFD bool // Whether to make use of the CgroupFD field.
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CgroupFD int // File descriptor of a cgroup to put the new process into.
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// PidFD, if not nil, is used to store the pidfd of a child, if the
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// functionality is supported by the kernel, or -1. Note *PidFD is
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// changed only if the process starts successfully.
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PidFD *int
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}
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var (
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none = [...]byte{'n', 'o', 'n', 'e', 0}
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slash = [...]byte{'/', 0}
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forceClone3 = false // Used by unit tests only.
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)
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// Implemented in runtime package.
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func runtime_BeforeFork()
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func runtime_AfterFork()
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func runtime_AfterForkInChild()
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// Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
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// If a dup or exec fails, write the errno error to pipe.
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// (Pipe is close-on-exec so if exec succeeds, it will be closed.)
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// In the child, this function must not acquire any locks, because
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// they might have been locked at the time of the fork. This means
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// no rescheduling, no malloc calls, and no new stack segments.
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// For the same reason compiler does not race instrument it.
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// The calls to RawSyscall are okay because they are assembly
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// functions that do not grow the stack.
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//
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//go:norace
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func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid int, err Errno) {
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// Set up and fork. This returns immediately in the parent or
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// if there's an error.
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upid, pidfd, err, mapPipe, locked := forkAndExecInChild1(argv0, argv, envv, chroot, dir, attr, sys, pipe)
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if locked {
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runtime_AfterFork()
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}
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if err != 0 {
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return 0, err
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}
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// parent; return PID
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pid = int(upid)
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if sys.PidFD != nil {
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*sys.PidFD = int(pidfd)
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}
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if sys.UidMappings != nil || sys.GidMappings != nil {
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Close(mapPipe[0])
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var err2 Errno
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// uid/gid mappings will be written after fork and unshare(2) for user
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// namespaces.
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if sys.Unshareflags&CLONE_NEWUSER == 0 {
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if err := writeUidGidMappings(pid, sys); err != nil {
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err2 = err.(Errno)
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}
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}
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RawSyscall(SYS_WRITE, uintptr(mapPipe[1]), uintptr(unsafe.Pointer(&err2)), unsafe.Sizeof(err2))
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Close(mapPipe[1])
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}
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return pid, 0
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}
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const _LINUX_CAPABILITY_VERSION_3 = 0x20080522
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type capHeader struct {
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version uint32
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pid int32
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}
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type capData struct {
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effective uint32
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permitted uint32
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inheritable uint32
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}
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type caps struct {
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hdr capHeader
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data [2]capData
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}
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// See CAP_TO_INDEX in linux/capability.h:
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func capToIndex(cap uintptr) uintptr { return cap >> 5 }
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// See CAP_TO_MASK in linux/capability.h:
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func capToMask(cap uintptr) uint32 { return 1 << uint(cap&31) }
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// cloneArgs holds arguments for clone3 Linux syscall.
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type cloneArgs struct {
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flags uint64 // Flags bit mask
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pidFD uint64 // Where to store PID file descriptor (int *)
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childTID uint64 // Where to store child TID, in child's memory (pid_t *)
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parentTID uint64 // Where to store child TID, in parent's memory (pid_t *)
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exitSignal uint64 // Signal to deliver to parent on child termination
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stack uint64 // Pointer to lowest byte of stack
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stackSize uint64 // Size of stack
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tls uint64 // Location of new TLS
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setTID uint64 // Pointer to a pid_t array (since Linux 5.5)
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setTIDSize uint64 // Number of elements in set_tid (since Linux 5.5)
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cgroup uint64 // File descriptor for target cgroup of child (since Linux 5.7)
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}
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// forkAndExecInChild1 implements the body of forkAndExecInChild up to
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// the parent's post-fork path. This is a separate function so we can
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// separate the child's and parent's stack frames if we're using
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// vfork.
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//
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// This is go:noinline because the point is to keep the stack frames
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// of this and forkAndExecInChild separate.
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//
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//go:noinline
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//go:norace
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//go:nocheckptr
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func forkAndExecInChild1(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid uintptr, pidfd int32, err1 Errno, mapPipe [2]int, locked bool) {
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// Defined in linux/prctl.h starting with Linux 4.3.
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const (
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PR_CAP_AMBIENT = 0x2f
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PR_CAP_AMBIENT_RAISE = 0x2
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)
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// vfork requires that the child not touch any of the parent's
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// active stack frames. Hence, the child does all post-fork
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// processing in this stack frame and never returns, while the
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// parent returns immediately from this frame and does all
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// post-fork processing in the outer frame.
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//
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// Declare all variables at top in case any
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// declarations require heap allocation (e.g., err2).
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// ":=" should not be used to declare any variable after
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// the call to runtime_BeforeFork.
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//
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// NOTE(bcmills): The allocation behavior described in the above comment
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// seems to lack a corresponding test, and it may be rendered invalid
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// by an otherwise-correct change in the compiler.
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var (
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err2 Errno
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nextfd int
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i int
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caps caps
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fd1, flags uintptr
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puid, psetgroups, pgid []byte
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uidmap, setgroups, gidmap []byte
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clone3 *cloneArgs
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pgrp int32
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dirfd int
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cred *Credential
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ngroups, groups uintptr
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c uintptr
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)
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pidfd = -1
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rlim := origRlimitNofile.Load()
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if sys.UidMappings != nil {
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puid = []byte("/proc/self/uid_map\000")
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uidmap = formatIDMappings(sys.UidMappings)
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}
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if sys.GidMappings != nil {
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psetgroups = []byte("/proc/self/setgroups\000")
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pgid = []byte("/proc/self/gid_map\000")
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if sys.GidMappingsEnableSetgroups {
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setgroups = []byte("allow\000")
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} else {
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setgroups = []byte("deny\000")
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}
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gidmap = formatIDMappings(sys.GidMappings)
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}
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// Record parent PID so child can test if it has died.
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ppid, _ := rawSyscallNoError(SYS_GETPID, 0, 0, 0)
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// Guard against side effects of shuffling fds below.
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// Make sure that nextfd is beyond any currently open files so
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// that we can't run the risk of overwriting any of them.
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fd := make([]int, len(attr.Files))
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nextfd = len(attr.Files)
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for i, ufd := range attr.Files {
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if nextfd < int(ufd) {
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nextfd = int(ufd)
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}
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fd[i] = int(ufd)
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}
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nextfd++
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// Allocate another pipe for parent to child communication for
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// synchronizing writing of User ID/Group ID mappings.
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if sys.UidMappings != nil || sys.GidMappings != nil {
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if err := forkExecPipe(mapPipe[:]); err != nil {
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err1 = err.(Errno)
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return
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}
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}
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flags = sys.Cloneflags
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if sys.Cloneflags&CLONE_NEWUSER == 0 && sys.Unshareflags&CLONE_NEWUSER == 0 {
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flags |= CLONE_VFORK | CLONE_VM
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}
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if sys.PidFD != nil {
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flags |= CLONE_PIDFD
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}
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// Whether to use clone3.
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if sys.UseCgroupFD || flags&CLONE_NEWTIME != 0 || forceClone3 {
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clone3 = &cloneArgs{
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flags: uint64(flags),
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exitSignal: uint64(SIGCHLD),
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}
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if sys.UseCgroupFD {
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clone3.flags |= CLONE_INTO_CGROUP
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clone3.cgroup = uint64(sys.CgroupFD)
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}
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if sys.PidFD != nil {
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clone3.pidFD = uint64(uintptr(unsafe.Pointer(&pidfd)))
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}
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}
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// About to call fork.
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// No more allocation or calls of non-assembly functions.
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runtime_BeforeFork()
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locked = true
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if clone3 != nil {
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pid, err1 = rawVforkSyscall(_SYS_clone3, uintptr(unsafe.Pointer(clone3)), unsafe.Sizeof(*clone3), 0)
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} else {
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flags |= uintptr(SIGCHLD)
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if runtime.GOARCH == "s390x" {
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// On Linux/s390, the first two arguments of clone(2) are swapped.
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pid, err1 = rawVforkSyscall(SYS_CLONE, 0, flags, uintptr(unsafe.Pointer(&pidfd)))
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} else {
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pid, err1 = rawVforkSyscall(SYS_CLONE, flags, 0, uintptr(unsafe.Pointer(&pidfd)))
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}
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}
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if err1 != 0 || pid != 0 {
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// If we're in the parent, we must return immediately
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// so we're not in the same stack frame as the child.
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// This can at most use the return PC, which the child
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// will not modify, and the results of
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// rawVforkSyscall, which must have been written after
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// the child was replaced.
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return
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}
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// Fork succeeded, now in child.
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// Enable the "keep capabilities" flag to set ambient capabilities later.
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if len(sys.AmbientCaps) > 0 {
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_, _, err1 = RawSyscall6(SYS_PRCTL, PR_SET_KEEPCAPS, 1, 0, 0, 0, 0)
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if err1 != 0 {
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goto childerror
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}
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}
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// Wait for User ID/Group ID mappings to be written.
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if sys.UidMappings != nil || sys.GidMappings != nil {
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if _, _, err1 = RawSyscall(SYS_CLOSE, uintptr(mapPipe[1]), 0, 0); err1 != 0 {
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goto childerror
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}
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pid, _, err1 = RawSyscall(SYS_READ, uintptr(mapPipe[0]), uintptr(unsafe.Pointer(&err2)), unsafe.Sizeof(err2))
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if err1 != 0 {
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goto childerror
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}
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if pid != unsafe.Sizeof(err2) {
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err1 = EINVAL
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goto childerror
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}
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if err2 != 0 {
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err1 = err2
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goto childerror
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}
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}
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// Session ID
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if sys.Setsid {
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_, _, err1 = RawSyscall(SYS_SETSID, 0, 0, 0)
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if err1 != 0 {
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goto childerror
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}
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}
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// Set process group
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if sys.Setpgid || sys.Foreground {
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// Place child in process group.
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_, _, err1 = RawSyscall(SYS_SETPGID, 0, uintptr(sys.Pgid), 0)
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if err1 != 0 {
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goto childerror
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}
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}
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if sys.Foreground {
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pgrp = int32(sys.Pgid)
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if pgrp == 0 {
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pid, _ = rawSyscallNoError(SYS_GETPID, 0, 0, 0)
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pgrp = int32(pid)
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}
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// Place process group in foreground.
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_, _, err1 = RawSyscall(SYS_IOCTL, uintptr(sys.Ctty), uintptr(TIOCSPGRP), uintptr(unsafe.Pointer(&pgrp)))
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if err1 != 0 {
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goto childerror
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}
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}
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// Restore the signal mask. We do this after TIOCSPGRP to avoid
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// having the kernel send a SIGTTOU signal to the process group.
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runtime_AfterForkInChild()
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// Unshare
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if sys.Unshareflags != 0 {
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_, _, err1 = RawSyscall(SYS_UNSHARE, sys.Unshareflags, 0, 0)
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if err1 != 0 {
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goto childerror
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}
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if sys.Unshareflags&CLONE_NEWUSER != 0 && sys.GidMappings != nil {
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dirfd = int(_AT_FDCWD)
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if fd1, _, err1 = RawSyscall6(SYS_OPENAT, uintptr(dirfd), uintptr(unsafe.Pointer(&psetgroups[0])), uintptr(O_WRONLY), 0, 0, 0); err1 != 0 {
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goto childerror
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}
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pid, _, err1 = RawSyscall(SYS_WRITE, fd1, uintptr(unsafe.Pointer(&setgroups[0])), uintptr(len(setgroups)))
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if err1 != 0 {
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goto childerror
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}
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if _, _, err1 = RawSyscall(SYS_CLOSE, fd1, 0, 0); err1 != 0 {
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goto childerror
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}
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if fd1, _, err1 = RawSyscall6(SYS_OPENAT, uintptr(dirfd), uintptr(unsafe.Pointer(&pgid[0])), uintptr(O_WRONLY), 0, 0, 0); err1 != 0 {
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goto childerror
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}
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pid, _, err1 = RawSyscall(SYS_WRITE, fd1, uintptr(unsafe.Pointer(&gidmap[0])), uintptr(len(gidmap)))
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if err1 != 0 {
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goto childerror
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}
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if _, _, err1 = RawSyscall(SYS_CLOSE, fd1, 0, 0); err1 != 0 {
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goto childerror
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}
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}
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if sys.Unshareflags&CLONE_NEWUSER != 0 && sys.UidMappings != nil {
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dirfd = int(_AT_FDCWD)
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if fd1, _, err1 = RawSyscall6(SYS_OPENAT, uintptr(dirfd), uintptr(unsafe.Pointer(&puid[0])), uintptr(O_WRONLY), 0, 0, 0); err1 != 0 {
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goto childerror
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}
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pid, _, err1 = RawSyscall(SYS_WRITE, fd1, uintptr(unsafe.Pointer(&uidmap[0])), uintptr(len(uidmap)))
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if err1 != 0 {
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goto childerror
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}
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if _, _, err1 = RawSyscall(SYS_CLOSE, fd1, 0, 0); err1 != 0 {
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goto childerror
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}
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}
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|
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// The unshare system call in Linux doesn't unshare mount points
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|
// mounted with --shared. Systemd mounts / with --shared. For a
|
|
// long discussion of the pros and cons of this see debian bug 739593.
|
|
// The Go model of unsharing is more like Plan 9, where you ask
|
|
// to unshare and the namespaces are unconditionally unshared.
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|
// To make this model work we must further mark / as MS_PRIVATE.
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|
// This is what the standard unshare command does.
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|
if sys.Unshareflags&CLONE_NEWNS == CLONE_NEWNS {
|
|
_, _, err1 = RawSyscall6(SYS_MOUNT, uintptr(unsafe.Pointer(&none[0])), uintptr(unsafe.Pointer(&slash[0])), 0, MS_REC|MS_PRIVATE, 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
}
|
|
|
|
// Chroot
|
|
if chroot != nil {
|
|
_, _, err1 = RawSyscall(SYS_CHROOT, uintptr(unsafe.Pointer(chroot)), 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// User and groups
|
|
if cred = sys.Credential; cred != nil {
|
|
ngroups = uintptr(len(cred.Groups))
|
|
groups = uintptr(0)
|
|
if ngroups > 0 {
|
|
groups = uintptr(unsafe.Pointer(&cred.Groups[0]))
|
|
}
|
|
if !(sys.GidMappings != nil && !sys.GidMappingsEnableSetgroups && ngroups == 0) && !cred.NoSetGroups {
|
|
_, _, err1 = RawSyscall(_SYS_setgroups, ngroups, groups, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
_, _, err1 = RawSyscall(sys_SETGID, uintptr(cred.Gid), 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
_, _, err1 = RawSyscall(sys_SETUID, uintptr(cred.Uid), 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
if len(sys.AmbientCaps) != 0 {
|
|
// Ambient capabilities were added in the 4.3 kernel,
|
|
// so it is safe to always use _LINUX_CAPABILITY_VERSION_3.
|
|
caps.hdr.version = _LINUX_CAPABILITY_VERSION_3
|
|
|
|
if _, _, err1 = RawSyscall(SYS_CAPGET, uintptr(unsafe.Pointer(&caps.hdr)), uintptr(unsafe.Pointer(&caps.data[0])), 0); err1 != 0 {
|
|
goto childerror
|
|
}
|
|
|
|
for _, c = range sys.AmbientCaps {
|
|
// Add the c capability to the permitted and inheritable capability mask,
|
|
// otherwise we will not be able to add it to the ambient capability mask.
|
|
caps.data[capToIndex(c)].permitted |= capToMask(c)
|
|
caps.data[capToIndex(c)].inheritable |= capToMask(c)
|
|
}
|
|
|
|
if _, _, err1 = RawSyscall(SYS_CAPSET, uintptr(unsafe.Pointer(&caps.hdr)), uintptr(unsafe.Pointer(&caps.data[0])), 0); err1 != 0 {
|
|
goto childerror
|
|
}
|
|
|
|
for _, c = range sys.AmbientCaps {
|
|
_, _, err1 = RawSyscall6(SYS_PRCTL, PR_CAP_AMBIENT, uintptr(PR_CAP_AMBIENT_RAISE), c, 0, 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
}
|
|
|
|
// Chdir
|
|
if dir != nil {
|
|
_, _, err1 = RawSyscall(SYS_CHDIR, uintptr(unsafe.Pointer(dir)), 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// Parent death signal
|
|
if sys.Pdeathsig != 0 {
|
|
_, _, err1 = RawSyscall6(SYS_PRCTL, PR_SET_PDEATHSIG, uintptr(sys.Pdeathsig), 0, 0, 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
|
|
// Signal self if parent is already dead. This might cause a
|
|
// duplicate signal in rare cases, but it won't matter when
|
|
// using SIGKILL.
|
|
pid, _ = rawSyscallNoError(SYS_GETPPID, 0, 0, 0)
|
|
if pid != ppid {
|
|
pid, _ = rawSyscallNoError(SYS_GETPID, 0, 0, 0)
|
|
_, _, err1 = RawSyscall(SYS_KILL, pid, uintptr(sys.Pdeathsig), 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
}
|
|
|
|
// Pass 1: look for fd[i] < i and move those up above len(fd)
|
|
// so that pass 2 won't stomp on an fd it needs later.
|
|
if pipe < nextfd {
|
|
_, _, err1 = RawSyscall(SYS_DUP3, uintptr(pipe), uintptr(nextfd), O_CLOEXEC)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
pipe = nextfd
|
|
nextfd++
|
|
}
|
|
for i = 0; i < len(fd); i++ {
|
|
if fd[i] >= 0 && fd[i] < i {
|
|
if nextfd == pipe { // don't stomp on pipe
|
|
nextfd++
|
|
}
|
|
_, _, err1 = RawSyscall(SYS_DUP3, uintptr(fd[i]), uintptr(nextfd), O_CLOEXEC)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
fd[i] = nextfd
|
|
nextfd++
|
|
}
|
|
}
|
|
|
|
// Pass 2: dup fd[i] down onto i.
|
|
for i = 0; i < len(fd); i++ {
|
|
if fd[i] == -1 {
|
|
RawSyscall(SYS_CLOSE, uintptr(i), 0, 0)
|
|
continue
|
|
}
|
|
if fd[i] == i {
|
|
// dup2(i, i) won't clear close-on-exec flag on Linux,
|
|
// probably not elsewhere either.
|
|
_, _, err1 = RawSyscall(fcntl64Syscall, uintptr(fd[i]), F_SETFD, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
continue
|
|
}
|
|
// The new fd is created NOT close-on-exec,
|
|
// which is exactly what we want.
|
|
_, _, err1 = RawSyscall(SYS_DUP3, uintptr(fd[i]), uintptr(i), 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// By convention, we don't close-on-exec the fds we are
|
|
// started with, so if len(fd) < 3, close 0, 1, 2 as needed.
|
|
// Programs that know they inherit fds >= 3 will need
|
|
// to set them close-on-exec.
|
|
for i = len(fd); i < 3; i++ {
|
|
RawSyscall(SYS_CLOSE, uintptr(i), 0, 0)
|
|
}
|
|
|
|
// Detach fd 0 from tty
|
|
if sys.Noctty {
|
|
_, _, err1 = RawSyscall(SYS_IOCTL, 0, uintptr(TIOCNOTTY), 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// Set the controlling TTY to Ctty
|
|
if sys.Setctty {
|
|
_, _, err1 = RawSyscall(SYS_IOCTL, uintptr(sys.Ctty), uintptr(TIOCSCTTY), 1)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// Restore original rlimit.
|
|
if rlim != nil {
|
|
rawSetrlimit(RLIMIT_NOFILE, rlim)
|
|
}
|
|
|
|
// Enable tracing if requested.
|
|
// Do this right before exec so that we don't unnecessarily trace the runtime
|
|
// setting up after the fork. See issue #21428.
|
|
if sys.Ptrace {
|
|
_, _, err1 = RawSyscall(SYS_PTRACE, uintptr(PTRACE_TRACEME), 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// Time to exec.
|
|
_, _, err1 = RawSyscall(SYS_EXECVE,
|
|
uintptr(unsafe.Pointer(argv0)),
|
|
uintptr(unsafe.Pointer(&argv[0])),
|
|
uintptr(unsafe.Pointer(&envv[0])))
|
|
|
|
childerror:
|
|
// send error code on pipe
|
|
RawSyscall(SYS_WRITE, uintptr(pipe), uintptr(unsafe.Pointer(&err1)), unsafe.Sizeof(err1))
|
|
for {
|
|
RawSyscall(SYS_EXIT, 253, 0, 0)
|
|
}
|
|
}
|
|
|
|
func formatIDMappings(idMap []SysProcIDMap) []byte {
|
|
var data []byte
|
|
for _, im := range idMap {
|
|
data = append(data, itoa.Itoa(im.ContainerID)+" "+itoa.Itoa(im.HostID)+" "+itoa.Itoa(im.Size)+"\n"...)
|
|
}
|
|
return data
|
|
}
|
|
|
|
// writeIDMappings writes the user namespace User ID or Group ID mappings to the specified path.
|
|
func writeIDMappings(path string, idMap []SysProcIDMap) error {
|
|
fd, err := Open(path, O_RDWR, 0)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
if _, err := Write(fd, formatIDMappings(idMap)); err != nil {
|
|
Close(fd)
|
|
return err
|
|
}
|
|
|
|
if err := Close(fd); err != nil {
|
|
return err
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// writeSetgroups writes to /proc/PID/setgroups "deny" if enable is false
|
|
// and "allow" if enable is true.
|
|
// This is needed since kernel 3.19, because you can't write gid_map without
|
|
// disabling setgroups() system call.
|
|
func writeSetgroups(pid int, enable bool) error {
|
|
sgf := "/proc/" + itoa.Itoa(pid) + "/setgroups"
|
|
fd, err := Open(sgf, O_RDWR, 0)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
var data []byte
|
|
if enable {
|
|
data = []byte("allow")
|
|
} else {
|
|
data = []byte("deny")
|
|
}
|
|
|
|
if _, err := Write(fd, data); err != nil {
|
|
Close(fd)
|
|
return err
|
|
}
|
|
|
|
return Close(fd)
|
|
}
|
|
|
|
// writeUidGidMappings writes User ID and Group ID mappings for user namespaces
|
|
// for a process and it is called from the parent process.
|
|
func writeUidGidMappings(pid int, sys *SysProcAttr) error {
|
|
if sys.UidMappings != nil {
|
|
uidf := "/proc/" + itoa.Itoa(pid) + "/uid_map"
|
|
if err := writeIDMappings(uidf, sys.UidMappings); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
if sys.GidMappings != nil {
|
|
// If the kernel is too old to support /proc/PID/setgroups, writeSetGroups will return ENOENT; this is OK.
|
|
if err := writeSetgroups(pid, sys.GidMappingsEnableSetgroups); err != nil && err != ENOENT {
|
|
return err
|
|
}
|
|
gidf := "/proc/" + itoa.Itoa(pid) + "/gid_map"
|
|
if err := writeIDMappings(gidf, sys.GidMappings); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
return nil
|
|
}
|