github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/syscalls/linux/vfs2/fscontext.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package vfs2
    16  
    17  import (
    18  	"github.com/SagerNet/gvisor/pkg/abi/linux"
    19  	"github.com/SagerNet/gvisor/pkg/errors/linuxerr"
    20  	"github.com/SagerNet/gvisor/pkg/fspath"
    21  	"github.com/SagerNet/gvisor/pkg/sentry/arch"
    22  	"github.com/SagerNet/gvisor/pkg/sentry/kernel"
    23  	"github.com/SagerNet/gvisor/pkg/sentry/vfs"
    24  	"github.com/SagerNet/gvisor/pkg/syserror"
    25  )
    26  
    27  // Getcwd implements Linux syscall getcwd(2).
    28  func Getcwd(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
    29  	addr := args[0].Pointer()
    30  	size := args[1].SizeT()
    31  
    32  	root := t.FSContext().RootDirectoryVFS2()
    33  	wd := t.FSContext().WorkingDirectoryVFS2()
    34  	s, err := t.Kernel().VFS().PathnameForGetcwd(t, root, wd)
    35  	root.DecRef(t)
    36  	wd.DecRef(t)
    37  	if err != nil {
    38  		return 0, nil, err
    39  	}
    40  
    41  	// Note this is >= because we need a terminator.
    42  	if uint(len(s)) >= size {
    43  		return 0, nil, syserror.ERANGE
    44  	}
    45  
    46  	// Construct a byte slice containing a NUL terminator.
    47  	buf := t.CopyScratchBuffer(len(s) + 1)
    48  	copy(buf, s)
    49  	buf[len(buf)-1] = 0
    50  
    51  	// Write the pathname slice.
    52  	n, err := t.CopyOutBytes(addr, buf)
    53  	if err != nil {
    54  		return 0, nil, err
    55  	}
    56  	return uintptr(n), nil, nil
    57  }
    58  
    59  // Chdir implements Linux syscall chdir(2).
    60  func Chdir(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
    61  	addr := args[0].Pointer()
    62  
    63  	path, err := copyInPath(t, addr)
    64  	if err != nil {
    65  		return 0, nil, err
    66  	}
    67  	tpop, err := getTaskPathOperation(t, linux.AT_FDCWD, path, disallowEmptyPath, followFinalSymlink)
    68  	if err != nil {
    69  		return 0, nil, err
    70  	}
    71  	defer tpop.Release(t)
    72  
    73  	vd, err := t.Kernel().VFS().GetDentryAt(t, t.Credentials(), &tpop.pop, &vfs.GetDentryOptions{
    74  		CheckSearchable: true,
    75  	})
    76  	if err != nil {
    77  		return 0, nil, err
    78  	}
    79  	t.FSContext().SetWorkingDirectoryVFS2(t, vd)
    80  	vd.DecRef(t)
    81  	return 0, nil, nil
    82  }
    83  
    84  // Fchdir implements Linux syscall fchdir(2).
    85  func Fchdir(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
    86  	fd := args[0].Int()
    87  
    88  	tpop, err := getTaskPathOperation(t, fd, fspath.Path{}, allowEmptyPath, nofollowFinalSymlink)
    89  	if err != nil {
    90  		return 0, nil, err
    91  	}
    92  	defer tpop.Release(t)
    93  
    94  	vd, err := t.Kernel().VFS().GetDentryAt(t, t.Credentials(), &tpop.pop, &vfs.GetDentryOptions{
    95  		CheckSearchable: true,
    96  	})
    97  	if err != nil {
    98  		return 0, nil, err
    99  	}
   100  	t.FSContext().SetWorkingDirectoryVFS2(t, vd)
   101  	vd.DecRef(t)
   102  	return 0, nil, nil
   103  }
   104  
   105  // Chroot implements Linux syscall chroot(2).
   106  func Chroot(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
   107  	addr := args[0].Pointer()
   108  
   109  	if !t.HasCapability(linux.CAP_SYS_CHROOT) {
   110  		return 0, nil, linuxerr.EPERM
   111  	}
   112  
   113  	path, err := copyInPath(t, addr)
   114  	if err != nil {
   115  		return 0, nil, err
   116  	}
   117  	tpop, err := getTaskPathOperation(t, linux.AT_FDCWD, path, disallowEmptyPath, followFinalSymlink)
   118  	if err != nil {
   119  		return 0, nil, err
   120  	}
   121  	defer tpop.Release(t)
   122  
   123  	vd, err := t.Kernel().VFS().GetDentryAt(t, t.Credentials(), &tpop.pop, &vfs.GetDentryOptions{
   124  		CheckSearchable: true,
   125  	})
   126  	if err != nil {
   127  		return 0, nil, err
   128  	}
   129  	t.FSContext().SetRootDirectoryVFS2(t, vd)
   130  	vd.DecRef(t)
   131  	return 0, nil, nil
   132  }