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// Copyright 2020 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package vfs2
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/fspath"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/fsbridge"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/loader"
slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/usermem"
)
// Execve implements linux syscall execve(2).
func Execve(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
pathnameAddr := args[0].Pointer()
argvAddr := args[1].Pointer()
envvAddr := args[2].Pointer()
return execveat(t, linux.AT_FDCWD, pathnameAddr, argvAddr, envvAddr, 0 /* flags */)
}
// Execveat implements linux syscall execveat(2).
func Execveat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
dirfd := args[0].Int()
pathnameAddr := args[1].Pointer()
argvAddr := args[2].Pointer()
envvAddr := args[3].Pointer()
flags := args[4].Int()
return execveat(t, dirfd, pathnameAddr, argvAddr, envvAddr, flags)
}
func execveat(t *kernel.Task, dirfd int32, pathnameAddr, argvAddr, envvAddr usermem.Addr, flags int32) (uintptr, *kernel.SyscallControl, error) {
if flags&^(linux.AT_EMPTY_PATH|linux.AT_SYMLINK_NOFOLLOW) != 0 {
return 0, nil, syserror.EINVAL
}
pathname, err := t.CopyInString(pathnameAddr, linux.PATH_MAX)
if err != nil {
return 0, nil, err
}
var argv, envv []string
if argvAddr != 0 {
var err error
argv, err = t.CopyInVector(argvAddr, slinux.ExecMaxElemSize, slinux.ExecMaxTotalSize)
if err != nil {
return 0, nil, err
}
}
if envvAddr != 0 {
var err error
envv, err = t.CopyInVector(envvAddr, slinux.ExecMaxElemSize, slinux.ExecMaxTotalSize)
if err != nil {
return 0, nil, err
}
}
root := t.FSContext().RootDirectoryVFS2()
defer root.DecRef(t)
var executable fsbridge.File
closeOnExec := false
if path := fspath.Parse(pathname); dirfd != linux.AT_FDCWD && !path.Absolute {
// We must open the executable ourselves since dirfd is used as the
// starting point while resolving path, but the task working directory
// is used as the starting point while resolving interpreters (Linux:
// fs/binfmt_script.c:load_script() => fs/exec.c:open_exec() =>
// do_open_execat(fd=AT_FDCWD)), and the loader package is currently
// incapable of handling this correctly.
if !path.HasComponents() && flags&linux.AT_EMPTY_PATH == 0 {
return 0, nil, syserror.ENOENT
}
dirfile, dirfileFlags := t.FDTable().GetVFS2(dirfd)
if dirfile == nil {
return 0, nil, syserror.EBADF
}
start := dirfile.VirtualDentry()
start.IncRef()
dirfile.DecRef(t)
closeOnExec = dirfileFlags.CloseOnExec
file, err := t.Kernel().VFS().OpenAt(t, t.Credentials(), &vfs.PathOperation{
Root: root,
Start: start,
Path: path,
FollowFinalSymlink: flags&linux.AT_SYMLINK_NOFOLLOW == 0,
}, &vfs.OpenOptions{
Flags: linux.O_RDONLY,
FileExec: true,
})
start.DecRef(t)
if err != nil {
return 0, nil, err
}
defer file.DecRef(t)
executable = fsbridge.NewVFSFile(file)
}
// Load the new TaskContext.
mntns := t.MountNamespaceVFS2()
wd := t.FSContext().WorkingDirectoryVFS2()
defer wd.DecRef(t)
remainingTraversals := uint(linux.MaxSymlinkTraversals)
loadArgs := loader.LoadArgs{
Opener: fsbridge.NewVFSLookup(mntns, root, wd),
RemainingTraversals: &remainingTraversals,
ResolveFinal: flags&linux.AT_SYMLINK_NOFOLLOW == 0,
Filename: pathname,
File: executable,
CloseOnExec: closeOnExec,
Argv: argv,
Envv: envv,
Features: t.Arch().FeatureSet(),
}
tc, se := t.Kernel().LoadTaskImage(t, loadArgs)
if se != nil {
return 0, nil, se.ToError()
}
ctrl, err := t.Execve(tc)
return 0, ctrl, err
}
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