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Diffstat (limited to 'pkg/sentry/kernel/shm/shm.go')
-rw-r--r--pkg/sentry/kernel/shm/shm.go156
1 files changed, 53 insertions, 103 deletions
diff --git a/pkg/sentry/kernel/shm/shm.go b/pkg/sentry/kernel/shm/shm.go
index f7ac4c2b2..459ae8c30 100644
--- a/pkg/sentry/kernel/shm/shm.go
+++ b/pkg/sentry/kernel/shm/shm.go
@@ -43,6 +43,7 @@ import (
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+ "gvisor.dev/gvisor/pkg/sentry/kernel/ipc"
ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/sentry/pgalloc"
@@ -51,12 +52,6 @@ import (
"gvisor.dev/gvisor/pkg/syserror"
)
-// Key represents a shm segment key. Analogous to a file name.
-type Key int32
-
-// ID represents the opaque handle for a shm segment. Analogous to an fd.
-type ID int32
-
// Registry tracks all shared memory segments in an IPC namespace. The registry
// provides the mechanisms for creating and finding segments, and reporting
// global shm parameters.
@@ -78,13 +73,13 @@ type Registry struct {
// exists a short window during which a Shm still exists in Shm, but is
// unreferenced. Users must use TryIncRef to determine if the Shm is
// still valid.
- shms map[ID]*Shm
+ shms map[ipc.ID]*Shm
// keysToShms maps segment keys to segments.
//
// Shms in keysToShms are guaranteed to be referenced, as they are
// removed by disassociateKey before the last DecRef.
- keysToShms map[Key]*Shm
+ keysToShms map[ipc.Key]*Shm
// Sum of the sizes of all existing segments rounded up to page size, in
// units of page size.
@@ -92,22 +87,22 @@ type Registry struct {
// ID assigned to the last created segment. Used to quickly find the next
// unused ID.
- lastIDUsed ID
+ lastIDUsed ipc.ID
}
// NewRegistry creates a new shm registry.
func NewRegistry(userNS *auth.UserNamespace) *Registry {
return &Registry{
userNS: userNS,
- shms: make(map[ID]*Shm),
- keysToShms: make(map[Key]*Shm),
+ shms: make(map[ipc.ID]*Shm),
+ keysToShms: make(map[ipc.Key]*Shm),
}
}
// FindByID looks up a segment given an ID.
//
// FindByID returns a reference on Shm.
-func (r *Registry) FindByID(id ID) *Shm {
+func (r *Registry) FindByID(id ipc.ID) *Shm {
r.mu.Lock()
defer r.mu.Unlock()
s := r.shms[id]
@@ -129,9 +124,9 @@ func (r *Registry) dissociateKey(s *Shm) {
defer r.mu.Unlock()
s.mu.Lock()
defer s.mu.Unlock()
- if s.key != linux.IPC_PRIVATE {
- delete(r.keysToShms, s.key)
- s.key = linux.IPC_PRIVATE
+ if s.obj.Key != linux.IPC_PRIVATE {
+ delete(r.keysToShms, s.obj.Key)
+ s.obj.Key = linux.IPC_PRIVATE
}
}
@@ -139,7 +134,7 @@ func (r *Registry) dissociateKey(s *Shm) {
// analogous to open(2).
//
// FindOrCreate returns a reference on Shm.
-func (r *Registry) FindOrCreate(ctx context.Context, pid int32, key Key, size uint64, mode linux.FileMode, private, create, exclusive bool) (*Shm, error) {
+func (r *Registry) FindOrCreate(ctx context.Context, pid int32, key ipc.Key, size uint64, mode linux.FileMode, private, create, exclusive bool) (*Shm, error) {
if (create || private) && (size < linux.SHMMIN || size > linux.SHMMAX) {
// "A new segment was to be created and size is less than SHMMIN or
// greater than SHMMAX." - man shmget(2)
@@ -165,7 +160,8 @@ func (r *Registry) FindOrCreate(ctx context.Context, pid int32, key Key, size ui
defer shm.mu.Unlock()
// Check that caller can access the segment.
- if !shm.checkPermissions(ctx, fs.PermsFromMode(mode)) {
+ creds := auth.CredentialsFromContext(ctx)
+ if !shm.obj.CheckPermissions(creds, fs.PermsFromMode(mode)) {
// "The user does not have permission to access the shared
// memory segment, and does not have the CAP_IPC_OWNER
// capability in the user namespace that governs its IPC
@@ -227,7 +223,7 @@ func (r *Registry) FindOrCreate(ctx context.Context, pid int32, key Key, size ui
// newShm creates a new segment in the registry.
//
// Precondition: Caller must hold r.mu.
-func (r *Registry) newShm(ctx context.Context, pid int32, key Key, creator fs.FileOwner, perms fs.FilePermissions, size uint64) (*Shm, error) {
+func (r *Registry) newShm(ctx context.Context, pid int32, key ipc.Key, creator fs.FileOwner, perms fs.FilePermissions, size uint64) (*Shm, error) {
mfp := pgalloc.MemoryFileProviderFromContext(ctx)
if mfp == nil {
panic(fmt.Sprintf("context.Context %T lacks non-nil value for key %T", ctx, pgalloc.CtxMemoryFileProvider))
@@ -239,21 +235,6 @@ func (r *Registry) newShm(ctx context.Context, pid int32, key Key, creator fs.Fi
return nil, err
}
- shm := &Shm{
- mfp: mfp,
- registry: r,
- creator: creator,
- size: size,
- effectiveSize: effectiveSize,
- fr: fr,
- key: key,
- perms: perms,
- owner: creator,
- creatorPID: pid,
- changeTime: ktime.NowFromContext(ctx),
- }
- shm.InitRefs()
-
// Find the next available ID.
for id := r.lastIDUsed + 1; id != r.lastIDUsed; id++ {
// Handle wrap around.
@@ -264,7 +245,18 @@ func (r *Registry) newShm(ctx context.Context, pid int32, key Key, creator fs.Fi
if r.shms[id] == nil {
r.lastIDUsed = id
- shm.ID = id
+ shm := &Shm{
+ mfp: mfp,
+ registry: r,
+ size: size,
+ effectiveSize: effectiveSize,
+ obj: ipc.NewObject(r.userNS, ipc.ID(id), ipc.Key(key), creator, creator, perms),
+ fr: fr,
+ creatorPID: pid,
+ changeTime: ktime.NowFromContext(ctx),
+ }
+ shm.InitRefs()
+
r.shms[id] = shm
r.keysToShms[key] = shm
@@ -314,11 +306,11 @@ func (r *Registry) remove(s *Shm) {
s.mu.Lock()
defer s.mu.Unlock()
- if s.key != linux.IPC_PRIVATE {
+ if s.obj.Key != linux.IPC_PRIVATE {
panic(fmt.Sprintf("Attempted to remove %s from the registry whose key is still associated", s.debugLocked()))
}
- delete(r.shms, s.ID)
+ delete(r.shms, s.obj.ID)
r.totalPages -= s.effectiveSize / hostarch.PageSize
}
@@ -374,12 +366,6 @@ type Shm struct {
// registry points to the shm registry containing this segment. Immutable.
registry *Registry
- // ID is the kernel identifier for this segment. Immutable.
- ID ID
-
- // creator is the user that created the segment. Immutable.
- creator fs.FileOwner
-
// size is the requested size of the segment at creation, in
// bytes. Immutable.
size uint64
@@ -397,14 +383,9 @@ type Shm struct {
// mu protects all fields below.
mu sync.Mutex `state:"nosave"`
- // key is the public identifier for this segment.
- key Key
+ // obj defines basic fields that should be included in all SysV IPC objects.
+ obj *ipc.Object
- // perms is the access permissions for the segment.
- perms fs.FilePermissions
-
- // owner of this segment.
- owner fs.FileOwner
// attachTime is updated on every successful shmat.
attachTime ktime.Time
// detachTime is updated on every successful shmdt.
@@ -426,17 +407,22 @@ type Shm struct {
pendingDestruction bool
}
+// ID returns object's ID.
+func (s *Shm) ID() ipc.ID {
+ return s.obj.ID
+}
+
// Precondition: Caller must hold s.mu.
func (s *Shm) debugLocked() string {
return fmt.Sprintf("Shm{id: %d, key: %d, size: %d bytes, refs: %d, destroyed: %v}",
- s.ID, s.key, s.size, s.ReadRefs(), s.pendingDestruction)
+ s.obj.ID, s.obj.Key, s.size, s.ReadRefs(), s.pendingDestruction)
}
// MappedName implements memmap.MappingIdentity.MappedName.
func (s *Shm) MappedName(ctx context.Context) string {
s.mu.Lock()
defer s.mu.Unlock()
- return fmt.Sprintf("SYSV%08d", s.key)
+ return fmt.Sprintf("SYSV%08d", s.obj.Key)
}
// DeviceID implements memmap.MappingIdentity.DeviceID.
@@ -448,7 +434,7 @@ func (s *Shm) DeviceID() uint64 {
func (s *Shm) InodeID() uint64 {
// "shmid gets reported as "inode#" in /proc/pid/maps. proc-ps tools use
// this. Changing this will break them." -- Linux, ipc/shm.c:newseg()
- return uint64(s.ID)
+ return uint64(s.obj.ID)
}
// DecRef drops a reference on s.
@@ -551,7 +537,8 @@ func (s *Shm) ConfigureAttach(ctx context.Context, addr hostarch.Addr, opts Atta
return memmap.MMapOpts{}, syserror.EIDRM
}
- if !s.checkPermissions(ctx, fs.PermMask{
+ creds := auth.CredentialsFromContext(ctx)
+ if !s.obj.CheckPermissions(creds, fs.PermMask{
Read: true,
Write: !opts.Readonly,
Execute: opts.Execute,
@@ -591,7 +578,8 @@ func (s *Shm) IPCStat(ctx context.Context) (*linux.ShmidDS, error) {
// "The caller must have read permission on the shared memory segment."
// - man shmctl(2)
- if !s.checkPermissions(ctx, fs.PermMask{Read: true}) {
+ creds := auth.CredentialsFromContext(ctx)
+ if !s.obj.CheckPermissions(creds, fs.PermMask{Read: true}) {
// "IPC_STAT or SHM_STAT is requested and shm_perm.mode does not allow
// read access for shmid, and the calling process does not have the
// CAP_IPC_OWNER capability in the user namespace that governs its IPC
@@ -603,7 +591,6 @@ func (s *Shm) IPCStat(ctx context.Context) (*linux.ShmidDS, error) {
if s.pendingDestruction {
mode |= linux.SHM_DEST
}
- creds := auth.CredentialsFromContext(ctx)
// Use the reference count as a rudimentary count of the number of
// attaches. We exclude:
@@ -620,12 +607,12 @@ func (s *Shm) IPCStat(ctx context.Context) (*linux.ShmidDS, error) {
ds := &linux.ShmidDS{
ShmPerm: linux.IPCPerm{
- Key: uint32(s.key),
- UID: uint32(creds.UserNamespace.MapFromKUID(s.owner.UID)),
- GID: uint32(creds.UserNamespace.MapFromKGID(s.owner.GID)),
- CUID: uint32(creds.UserNamespace.MapFromKUID(s.creator.UID)),
- CGID: uint32(creds.UserNamespace.MapFromKGID(s.creator.GID)),
- Mode: mode | uint16(s.perms.LinuxMode()),
+ Key: uint32(s.obj.Key),
+ UID: uint32(creds.UserNamespace.MapFromKUID(s.obj.Owner.UID)),
+ GID: uint32(creds.UserNamespace.MapFromKGID(s.obj.Owner.GID)),
+ CUID: uint32(creds.UserNamespace.MapFromKUID(s.obj.Creator.UID)),
+ CGID: uint32(creds.UserNamespace.MapFromKGID(s.obj.Creator.GID)),
+ Mode: mode | uint16(s.obj.Perms.LinuxMode()),
Seq: 0, // IPC sequences not supported.
},
ShmSegsz: s.size,
@@ -645,11 +632,11 @@ func (s *Shm) Set(ctx context.Context, ds *linux.ShmidDS) error {
s.mu.Lock()
defer s.mu.Unlock()
- if !s.checkOwnership(ctx) {
+ creds := auth.CredentialsFromContext(ctx)
+ if !s.obj.CheckOwnership(creds) {
return linuxerr.EPERM
}
- creds := auth.CredentialsFromContext(ctx)
uid := creds.UserNamespace.MapToKUID(auth.UID(ds.ShmPerm.UID))
gid := creds.UserNamespace.MapToKGID(auth.GID(ds.ShmPerm.GID))
if !uid.Ok() || !gid.Ok() {
@@ -659,10 +646,10 @@ func (s *Shm) Set(ctx context.Context, ds *linux.ShmidDS) error {
// User may only modify the lower 9 bits of the mode. All the other bits are
// always 0 for the underlying inode.
mode := linux.FileMode(ds.ShmPerm.Mode & 0x1ff)
- s.perms = fs.FilePermsFromMode(mode)
+ s.obj.Perms = fs.FilePermsFromMode(mode)
- s.owner.UID = uid
- s.owner.GID = gid
+ s.obj.Owner.UID = uid
+ s.obj.Owner.GID = gid
s.changeTime = ktime.NowFromContext(ctx)
return nil
@@ -691,40 +678,3 @@ func (s *Shm) MarkDestroyed(ctx context.Context) {
s.DecRef(ctx)
return
}
-
-// checkOwnership verifies whether a segment may be accessed by ctx as an
-// owner. See ipc/util.c:ipcctl_pre_down_nolock() in Linux.
-//
-// Precondition: Caller must hold s.mu.
-func (s *Shm) checkOwnership(ctx context.Context) bool {
- creds := auth.CredentialsFromContext(ctx)
- if s.owner.UID == creds.EffectiveKUID || s.creator.UID == creds.EffectiveKUID {
- return true
- }
-
- // Tasks with CAP_SYS_ADMIN may bypass ownership checks. Strangely, Linux
- // doesn't use CAP_IPC_OWNER for this despite CAP_IPC_OWNER being documented
- // for use to "override IPC ownership checks".
- return creds.HasCapabilityIn(linux.CAP_SYS_ADMIN, s.registry.userNS)
-}
-
-// checkPermissions verifies whether a segment is accessible by ctx for access
-// described by req. See ipc/util.c:ipcperms() in Linux.
-//
-// Precondition: Caller must hold s.mu.
-func (s *Shm) checkPermissions(ctx context.Context, req fs.PermMask) bool {
- creds := auth.CredentialsFromContext(ctx)
-
- p := s.perms.Other
- if s.owner.UID == creds.EffectiveKUID {
- p = s.perms.User
- } else if creds.InGroup(s.owner.GID) {
- p = s.perms.Group
- }
- if p.SupersetOf(req) {
- return true
- }
-
- // Tasks with CAP_IPC_OWNER may bypass permission checks.
- return creds.HasCapabilityIn(linux.CAP_IPC_OWNER, s.registry.userNS)
-}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-03 04:09:54 +0000