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// Copyright 2018 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 proc
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/context"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
"gvisor.dev/gvisor/pkg/sentry/fs/proc/device"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/mm"
"gvisor.dev/gvisor/pkg/sentry/usermem"
)
// taskOwnedInodeOps wraps an fs.InodeOperations and overrides the UnstableAttr
// method to return either the task or root as the owner, depending on the
// task's dumpability.
//
// +stateify savable
type taskOwnedInodeOps struct {
fs.InodeOperations
// t is the task that owns this file.
t *kernel.Task
}
// UnstableAttr implement fs.InodeOperations.UnstableAttr.
func (i *taskOwnedInodeOps) UnstableAttr(ctx context.Context, inode *fs.Inode) (fs.UnstableAttr, error) {
uattr, err := i.InodeOperations.UnstableAttr(ctx, inode)
if err != nil {
return fs.UnstableAttr{}, err
}
// By default, set the task owner as the file owner.
creds := i.t.Credentials()
uattr.Owner = fs.FileOwner{creds.EffectiveKUID, creds.EffectiveKGID}
// Linux doesn't apply dumpability adjustments to world
// readable/executable directories so that applications can stat
// /proc/PID to determine the effective UID of a process. See
// fs/proc/base.c:task_dump_owner.
if fs.IsDir(inode.StableAttr) && uattr.Perms == fs.FilePermsFromMode(0555) {
return uattr, nil
}
// If the task is not dumpable, then root (in the namespace preferred)
// owns the file.
var m *mm.MemoryManager
i.t.WithMuLocked(func(t *kernel.Task) {
m = t.MemoryManager()
})
if m == nil {
uattr.Owner.UID = auth.RootKUID
uattr.Owner.GID = auth.RootKGID
} else if m.Dumpability() != mm.UserDumpable {
if kuid := creds.UserNamespace.MapToKUID(auth.RootUID); kuid.Ok() {
uattr.Owner.UID = kuid
} else {
uattr.Owner.UID = auth.RootKUID
}
if kgid := creds.UserNamespace.MapToKGID(auth.RootGID); kgid.Ok() {
uattr.Owner.GID = kgid
} else {
uattr.Owner.GID = auth.RootKGID
}
}
return uattr, nil
}
// staticFileInodeOps is an InodeOperations implementation that can be used to
// return file contents which are constant. This file is not writable and will
// always have mode 0444.
//
// +stateify savable
type staticFileInodeOps struct {
fsutil.InodeDenyWriteChecker `state:"nosave"`
fsutil.InodeNoExtendedAttributes `state:"nosave"`
fsutil.InodeNoopAllocate `state:"nosave"`
fsutil.InodeNoopRelease `state:"nosave"`
fsutil.InodeNoopTruncate `state:"nosave"`
fsutil.InodeNoopWriteOut `state:"nosave"`
fsutil.InodeNotDirectory `state:"nosave"`
fsutil.InodeNotMappable `state:"nosave"`
fsutil.InodeNotSocket `state:"nosave"`
fsutil.InodeNotSymlink `state:"nosave"`
fsutil.InodeVirtual `state:"nosave"`
fsutil.InodeSimpleAttributes
fsutil.InodeStaticFileGetter
}
var _ fs.InodeOperations = (*staticFileInodeOps)(nil)
// newStaticFileInode returns a procfs InodeOperations with static contents.
func newStaticProcInode(ctx context.Context, msrc *fs.MountSource, contents []byte) *fs.Inode {
iops := &staticFileInodeOps{
InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, fs.RootOwner, fs.FilePermsFromMode(0444), linux.PROC_SUPER_MAGIC),
InodeStaticFileGetter: fsutil.InodeStaticFileGetter{
Contents: contents,
},
}
return newProcInode(iops, msrc, fs.SpecialFile, nil)
}
// newProcInode creates a new inode from the given inode operations.
func newProcInode(iops fs.InodeOperations, msrc *fs.MountSource, typ fs.InodeType, t *kernel.Task) *fs.Inode {
sattr := fs.StableAttr{
DeviceID: device.ProcDevice.DeviceID(),
InodeID: device.ProcDevice.NextIno(),
BlockSize: usermem.PageSize,
Type: typ,
}
if t != nil {
iops = &taskOwnedInodeOps{iops, t}
}
return fs.NewInode(iops, msrc, sattr)
}
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