summaryrefslogtreecommitdiffhomepage
path: root/pkg/sentry/kernel
diff options
context:
space:
mode:
Diffstat (limited to 'pkg/sentry/kernel')
-rw-r--r--pkg/sentry/kernel/rseq.go383
-rw-r--r--pkg/sentry/kernel/shm/shm.go85
-rw-r--r--pkg/sentry/kernel/task.go43
-rw-r--r--pkg/sentry/kernel/task_clone.go7
-rw-r--r--pkg/sentry/kernel/task_exec.go6
-rw-r--r--pkg/sentry/kernel/task_run.go16
-rw-r--r--pkg/sentry/kernel/task_start.go10
-rw-r--r--pkg/sentry/kernel/thread_group.go18
8 files changed, 471 insertions, 97 deletions
diff --git a/pkg/sentry/kernel/rseq.go b/pkg/sentry/kernel/rseq.go
index 24ea002ba..b14429854 100644
--- a/pkg/sentry/kernel/rseq.go
+++ b/pkg/sentry/kernel/rseq.go
@@ -15,17 +15,29 @@
package kernel
import (
+ "fmt"
+
+ "gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/hostcpu"
"gvisor.dev/gvisor/pkg/sentry/usermem"
"gvisor.dev/gvisor/pkg/syserror"
)
-// Restartable sequences, as described in https://lwn.net/Articles/650333/.
+// Restartable sequences.
+//
+// We support two different APIs for restartable sequences.
+//
+// 1. The upstream interface added in v4.18.
+// 2. The interface described in https://lwn.net/Articles/650333/.
+//
+// Throughout this file and other parts of the kernel, the latter is referred
+// to as "old rseq". This interface was never merged upstream, but is supported
+// for a limited set of applications that use it regardless.
-// RSEQCriticalRegion describes a restartable sequence critical region.
+// OldRSeqCriticalRegion describes an old rseq critical region.
//
// +stateify savable
-type RSEQCriticalRegion struct {
+type OldRSeqCriticalRegion struct {
// When a task in this thread group has its CPU preempted (as defined by
// platform.ErrContextCPUPreempted) or has a signal delivered to an
// application handler while its instruction pointer is in CriticalSection,
@@ -35,86 +47,359 @@ type RSEQCriticalRegion struct {
Restart usermem.Addr
}
-// RSEQAvailable returns true if t supports restartable sequences.
-func (t *Task) RSEQAvailable() bool {
+// RSeqAvailable returns true if t supports (old and new) restartable sequences.
+func (t *Task) RSeqAvailable() bool {
return t.k.useHostCores && t.k.Platform.DetectsCPUPreemption()
}
-// RSEQCriticalRegion returns a copy of t's thread group's current restartable
-// sequence.
-func (t *Task) RSEQCriticalRegion() RSEQCriticalRegion {
- return *t.tg.rscr.Load().(*RSEQCriticalRegion)
+// SetRSeq registers addr as this thread's rseq structure.
+//
+// Preconditions: The caller must be running on the task goroutine.
+func (t *Task) SetRSeq(addr usermem.Addr, length, signature uint32) error {
+ if t.rseqAddr != 0 {
+ if t.rseqAddr != addr {
+ return syserror.EINVAL
+ }
+ if t.rseqSignature != signature {
+ return syserror.EINVAL
+ }
+ return syserror.EBUSY
+ }
+
+ // rseq must be aligned and correctly sized.
+ if addr&(linux.AlignOfRSeq-1) != 0 {
+ return syserror.EINVAL
+ }
+ if length != linux.SizeOfRSeq {
+ return syserror.EINVAL
+ }
+ if _, ok := t.MemoryManager().CheckIORange(addr, linux.SizeOfRSeq); !ok {
+ return syserror.EFAULT
+ }
+
+ t.rseqAddr = addr
+ t.rseqSignature = signature
+
+ // Initialize the CPUID.
+ //
+ // Linux implicitly does this on return from userspace, where failure
+ // would cause SIGSEGV.
+ if err := t.rseqUpdateCPU(); err != nil {
+ t.rseqAddr = 0
+ t.rseqSignature = 0
+
+ t.Debugf("Failed to copy CPU to %#x for rseq: %v", t.rseqAddr, err)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return syserror.EFAULT
+ }
+
+ return nil
}
-// SetRSEQCriticalRegion replaces t's thread group's restartable sequence.
+// ClearRSeq unregisters addr as this thread's rseq structure.
//
-// Preconditions: t.RSEQAvailable() == true.
-func (t *Task) SetRSEQCriticalRegion(rscr RSEQCriticalRegion) error {
+// Preconditions: The caller must be running on the task goroutine.
+func (t *Task) ClearRSeq(addr usermem.Addr, length, signature uint32) error {
+ if t.rseqAddr == 0 {
+ return syserror.EINVAL
+ }
+ if t.rseqAddr != addr {
+ return syserror.EINVAL
+ }
+ if length != linux.SizeOfRSeq {
+ return syserror.EINVAL
+ }
+ if t.rseqSignature != signature {
+ return syserror.EPERM
+ }
+
+ if err := t.rseqClearCPU(); err != nil {
+ return err
+ }
+
+ t.rseqAddr = 0
+ t.rseqSignature = 0
+
+ if t.oldRSeqCPUAddr == 0 {
+ // rseqCPU no longer needed.
+ t.rseqCPU = -1
+ }
+
+ return nil
+}
+
+// OldRSeqCriticalRegion returns a copy of t's thread group's current
+// old restartable sequence.
+func (t *Task) OldRSeqCriticalRegion() OldRSeqCriticalRegion {
+ return *t.tg.oldRSeqCritical.Load().(*OldRSeqCriticalRegion)
+}
+
+// SetOldRSeqCriticalRegion replaces t's thread group's old restartable
+// sequence.
+//
+// Preconditions: t.RSeqAvailable() == true.
+func (t *Task) SetOldRSeqCriticalRegion(r OldRSeqCriticalRegion) error {
// These checks are somewhat more lenient than in Linux, which (bizarrely)
- // requires rscr.CriticalSection to be non-empty and rscr.Restart to be
- // outside of rscr.CriticalSection, even if rscr.CriticalSection.Start == 0
+ // requires r.CriticalSection to be non-empty and r.Restart to be
+ // outside of r.CriticalSection, even if r.CriticalSection.Start == 0
// (which disables the critical region).
- if rscr.CriticalSection.Start == 0 {
- rscr.CriticalSection.End = 0
- rscr.Restart = 0
- t.tg.rscr.Store(&rscr)
+ if r.CriticalSection.Start == 0 {
+ r.CriticalSection.End = 0
+ r.Restart = 0
+ t.tg.oldRSeqCritical.Store(&r)
return nil
}
- if rscr.CriticalSection.Start >= rscr.CriticalSection.End {
+ if r.CriticalSection.Start >= r.CriticalSection.End {
return syserror.EINVAL
}
- if rscr.CriticalSection.Contains(rscr.Restart) {
+ if r.CriticalSection.Contains(r.Restart) {
return syserror.EINVAL
}
- // TODO(jamieliu): check that rscr.CriticalSection and rscr.Restart are in
- // the application address range, for consistency with Linux
- t.tg.rscr.Store(&rscr)
+ // TODO(jamieliu): check that r.CriticalSection and r.Restart are in
+ // the application address range, for consistency with Linux.
+ t.tg.oldRSeqCritical.Store(&r)
return nil
}
-// RSEQCPUAddr returns the address that RSEQ will keep updated with t's CPU
-// number.
+// OldRSeqCPUAddr returns the address that old rseq will keep updated with t's
+// CPU number.
//
// Preconditions: The caller must be running on the task goroutine.
-func (t *Task) RSEQCPUAddr() usermem.Addr {
- return t.rseqCPUAddr
+func (t *Task) OldRSeqCPUAddr() usermem.Addr {
+ return t.oldRSeqCPUAddr
}
-// SetRSEQCPUAddr replaces the address that RSEQ will keep updated with t's CPU
-// number.
+// SetOldRSeqCPUAddr replaces the address that old rseq will keep updated with
+// t's CPU number.
//
-// Preconditions: t.RSEQAvailable() == true. The caller must be running on the
+// Preconditions: t.RSeqAvailable() == true. The caller must be running on the
// task goroutine. t's AddressSpace must be active.
-func (t *Task) SetRSEQCPUAddr(addr usermem.Addr) error {
- t.rseqCPUAddr = addr
- if addr != 0 {
- t.rseqCPU = int32(hostcpu.GetCPU())
- if err := t.rseqCopyOutCPU(); err != nil {
- t.rseqCPUAddr = 0
- t.rseqCPU = -1
- return syserror.EINVAL // yes, EINVAL, not err or EFAULT
- }
- } else {
- t.rseqCPU = -1
+func (t *Task) SetOldRSeqCPUAddr(addr usermem.Addr) error {
+ t.oldRSeqCPUAddr = addr
+
+ // Check that addr is writable.
+ //
+ // N.B. rseqUpdateCPU may fail on a bad t.rseqAddr as well. That's
+ // unfortunate, but unlikely in a correct program.
+ if err := t.rseqUpdateCPU(); err != nil {
+ t.oldRSeqCPUAddr = 0
+ return syserror.EINVAL // yes, EINVAL, not err or EFAULT
}
return nil
}
// Preconditions: The caller must be running on the task goroutine. t's
// AddressSpace must be active.
-func (t *Task) rseqCopyOutCPU() error {
+func (t *Task) rseqUpdateCPU() error {
+ if t.rseqAddr == 0 && t.oldRSeqCPUAddr == 0 {
+ t.rseqCPU = -1
+ return nil
+ }
+
+ t.rseqCPU = int32(hostcpu.GetCPU())
+
+ // Update both CPUs, even if one fails.
+ rerr := t.rseqCopyOutCPU()
+ oerr := t.oldRSeqCopyOutCPU()
+
+ if rerr != nil {
+ return rerr
+ }
+ return oerr
+}
+
+// Preconditions: The caller must be running on the task goroutine. t's
+// AddressSpace must be active.
+func (t *Task) oldRSeqCopyOutCPU() error {
+ if t.oldRSeqCPUAddr == 0 {
+ return nil
+ }
+
buf := t.CopyScratchBuffer(4)
usermem.ByteOrder.PutUint32(buf, uint32(t.rseqCPU))
- _, err := t.CopyOutBytes(t.rseqCPUAddr, buf)
+ _, err := t.CopyOutBytes(t.oldRSeqCPUAddr, buf)
+ return err
+}
+
+// Preconditions: The caller must be running on the task goroutine. t's
+// AddressSpace must be active.
+func (t *Task) rseqCopyOutCPU() error {
+ if t.rseqAddr == 0 {
+ return nil
+ }
+
+ buf := t.CopyScratchBuffer(8)
+ // CPUIDStart and CPUID are the first two fields in linux.RSeq.
+ usermem.ByteOrder.PutUint32(buf, uint32(t.rseqCPU)) // CPUIDStart
+ usermem.ByteOrder.PutUint32(buf[4:], uint32(t.rseqCPU)) // CPUID
+ // N.B. This write is not atomic, but since this occurs on the task
+ // goroutine then as long as userspace uses a single-instruction read
+ // it can't see an invalid value.
+ _, err := t.CopyOutBytes(t.rseqAddr, buf)
+ return err
+}
+
+// Preconditions: The caller must be running on the task goroutine. t's
+// AddressSpace must be active.
+func (t *Task) rseqClearCPU() error {
+ buf := t.CopyScratchBuffer(8)
+ // CPUIDStart and CPUID are the first two fields in linux.RSeq.
+ usermem.ByteOrder.PutUint32(buf, 0) // CPUIDStart
+ usermem.ByteOrder.PutUint32(buf[4:], linux.RSEQ_CPU_ID_UNINITIALIZED) // CPUID
+ // N.B. This write is not atomic, but since this occurs on the task
+ // goroutine then as long as userspace uses a single-instruction read
+ // it can't see an invalid value.
+ _, err := t.CopyOutBytes(t.rseqAddr, buf)
return err
}
+// rseqAddrInterrupt checks if IP is in a critical section, and aborts if so.
+//
+// This is a bit complex since both the RSeq and RSeqCriticalSection structs
+// are stored in userspace. So we must:
+//
+// 1. Copy in the address of RSeqCriticalSection from RSeq.
+// 2. Copy in RSeqCriticalSection itself.
+// 3. Validate critical section struct version, address range, abort address.
+// 4. Validate the abort signature (4 bytes preceding abort IP match expected
+// signature).
+// 5. Clear address of RSeqCriticalSection from RSeq.
+// 6. Finally, conditionally abort.
+//
+// See kernel/rseq.c:rseq_ip_fixup for reference.
+//
+// Preconditions: The caller must be running on the task goroutine. t's
+// AddressSpace must be active.
+func (t *Task) rseqAddrInterrupt() {
+ if t.rseqAddr == 0 {
+ return
+ }
+
+ critAddrAddr, ok := t.rseqAddr.AddLength(linux.OffsetOfRSeqCriticalSection)
+ if !ok {
+ // SetRSeq should validate this.
+ panic(fmt.Sprintf("t.rseqAddr (%#x) not large enough", t.rseqAddr))
+ }
+
+ if t.Arch().Width() != 8 {
+ // We only handle 64-bit for now.
+ t.Debugf("Only 64-bit rseq supported.")
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ buf := t.CopyScratchBuffer(8)
+ if _, err := t.CopyInBytes(critAddrAddr, buf); err != nil {
+ t.Debugf("Failed to copy critical section address from %#x for rseq: %v", critAddrAddr, err)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ critAddr := usermem.Addr(usermem.ByteOrder.Uint64(buf))
+ if critAddr == 0 {
+ return
+ }
+
+ buf = t.CopyScratchBuffer(linux.SizeOfRSeqCriticalSection)
+ if _, err := t.CopyInBytes(critAddr, buf); err != nil {
+ t.Debugf("Failed to copy critical section from %#x for rseq: %v", critAddr, err)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ // Manually marshal RSeqCriticalSection as this is in the hot path when
+ // rseq is enabled. It must be as fast as possible.
+ //
+ // TODO(b/130243041): Replace with go_marshal.
+ cs := linux.RSeqCriticalSection{
+ Version: usermem.ByteOrder.Uint32(buf[0:4]),
+ Flags: usermem.ByteOrder.Uint32(buf[4:8]),
+ Start: usermem.ByteOrder.Uint64(buf[8:16]),
+ PostCommitOffset: usermem.ByteOrder.Uint64(buf[16:24]),
+ Abort: usermem.ByteOrder.Uint64(buf[24:32]),
+ }
+
+ if cs.Version != 0 {
+ t.Debugf("Unknown version in %+v", cs)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ start := usermem.Addr(cs.Start)
+ critRange, ok := start.ToRange(cs.PostCommitOffset)
+ if !ok {
+ t.Debugf("Invalid start and offset in %+v", cs)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ abort := usermem.Addr(cs.Abort)
+ if critRange.Contains(abort) {
+ t.Debugf("Abort in critical section in %+v", cs)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ // Verify signature.
+ sigAddr := abort - linux.SizeOfRSeqSignature
+
+ buf = t.CopyScratchBuffer(linux.SizeOfRSeqSignature)
+ if _, err := t.CopyInBytes(sigAddr, buf); err != nil {
+ t.Debugf("Failed to copy critical section signature from %#x for rseq: %v", sigAddr, err)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ sig := usermem.ByteOrder.Uint32(buf)
+ if sig != t.rseqSignature {
+ t.Debugf("Mismatched rseq signature %d != %d", sig, t.rseqSignature)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ // Clear the critical section address.
+ //
+ // NOTE(b/143949567): We don't support any rseq flags, so we always
+ // restart if we are in the critical section, and thus *always* clear
+ // critAddrAddr.
+ if _, err := t.MemoryManager().ZeroOut(t, critAddrAddr, int64(t.Arch().Width()), usermem.IOOpts{
+ AddressSpaceActive: true,
+ }); err != nil {
+ t.Debugf("Failed to clear critical section address from %#x for rseq: %v", critAddrAddr, err)
+ t.forceSignal(linux.SIGSEGV, false /* unconditional */)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ return
+ }
+
+ // Finally we can actually decide whether or not to restart.
+ if !critRange.Contains(usermem.Addr(t.Arch().IP())) {
+ return
+ }
+
+ t.Arch().SetIP(uintptr(cs.Abort))
+}
+
// Preconditions: The caller must be running on the task goroutine.
-func (t *Task) rseqInterrupt() {
- rscr := t.tg.rscr.Load().(*RSEQCriticalRegion)
- if ip := t.Arch().IP(); rscr.CriticalSection.Contains(usermem.Addr(ip)) {
- t.Debugf("Interrupted RSEQ critical section at %#x; restarting at %#x", ip, rscr.Restart)
- t.Arch().SetIP(uintptr(rscr.Restart))
- t.Arch().SetRSEQInterruptedIP(ip)
+func (t *Task) oldRSeqInterrupt() {
+ r := t.tg.oldRSeqCritical.Load().(*OldRSeqCriticalRegion)
+ if ip := t.Arch().IP(); r.CriticalSection.Contains(usermem.Addr(ip)) {
+ t.Debugf("Interrupted rseq critical section at %#x; restarting at %#x", ip, r.Restart)
+ t.Arch().SetIP(uintptr(r.Restart))
+ t.Arch().SetOldRSeqInterruptedIP(ip)
}
}
+
+// Preconditions: The caller must be running on the task goroutine.
+func (t *Task) rseqInterrupt() {
+ t.rseqAddrInterrupt()
+ t.oldRSeqInterrupt()
+}
diff --git a/pkg/sentry/kernel/shm/shm.go b/pkg/sentry/kernel/shm/shm.go
index 5bd610f68..19034a21e 100644
--- a/pkg/sentry/kernel/shm/shm.go
+++ b/pkg/sentry/kernel/shm/shm.go
@@ -71,9 +71,20 @@ type Registry struct {
mu sync.Mutex `state:"nosave"`
// shms maps segment ids to segments.
+ //
+ // shms holds all referenced segments, which are removed on the last
+ // DecRef. Thus, it cannot itself hold a reference on the Shm.
+ //
+ // Since removal only occurs after the last (unlocked) DecRef, there
+ // 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
// 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
// Sum of the sizes of all existing segments rounded up to page size, in
@@ -95,10 +106,18 @@ func NewRegistry(userNS *auth.UserNamespace) *Registry {
}
// FindByID looks up a segment given an ID.
+//
+// FindByID returns a reference on Shm.
func (r *Registry) FindByID(id ID) *Shm {
r.mu.Lock()
defer r.mu.Unlock()
- return r.shms[id]
+ s := r.shms[id]
+ // Take a reference on s. If TryIncRef fails, s has reached the last
+ // DecRef, but hasn't quite been removed from r.shms yet.
+ if s != nil && s.TryIncRef() {
+ return s
+ }
+ return nil
}
// dissociateKey removes the association between a segment and its key,
@@ -119,6 +138,8 @@ func (r *Registry) dissociateKey(s *Shm) {
// FindOrCreate looks up or creates a segment in the registry. It's functionally
// 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) {
if (create || private) && (size < linux.SHMMIN || size > linux.SHMMAX) {
// "A new segment was to be created and size is less than SHMMIN or
@@ -166,6 +187,7 @@ func (r *Registry) FindOrCreate(ctx context.Context, pid int32, key Key, size ui
return nil, syserror.EEXIST
}
+ shm.IncRef()
return shm, nil
}
@@ -193,7 +215,14 @@ func (r *Registry) FindOrCreate(ctx context.Context, pid int32, key Key, size ui
// Need to create a new segment.
creator := fs.FileOwnerFromContext(ctx)
perms := fs.FilePermsFromMode(mode)
- return r.newShm(ctx, pid, key, creator, perms, size)
+ s, err := r.newShm(ctx, pid, key, creator, perms, size)
+ if err != nil {
+ return nil, err
+ }
+ // The initial reference is held by s itself. Take another to return to
+ // the caller.
+ s.IncRef()
+ return s, nil
}
// newShm creates a new segment in the registry.
@@ -296,22 +325,26 @@ func (r *Registry) remove(s *Shm) {
// Shm represents a single shared memory segment.
//
-// Shm segment are backed directly by an allocation from platform
-// memory. Segments are always mapped as a whole, greatly simplifying how
-// mappings are tracked. However note that mremap and munmap calls may cause the
-// vma for a segment to become fragmented; which requires special care when
-// unmapping a segment. See mm/shm.go.
+// Shm segment are backed directly by an allocation from platform memory.
+// Segments are always mapped as a whole, greatly simplifying how mappings are
+// tracked. However note that mremap and munmap calls may cause the vma for a
+// segment to become fragmented; which requires special care when unmapping a
+// segment. See mm/shm.go.
//
// Segments persist until they are explicitly marked for destruction via
-// shmctl(SHM_RMID).
+// MarkDestroyed().
//
// Shm implements memmap.Mappable and memmap.MappingIdentity.
//
// +stateify savable
type Shm struct {
- // AtomicRefCount tracks the number of references to this segment from
- // maps. A segment always holds a reference to itself, until it's marked for
+ // AtomicRefCount tracks the number of references to this segment.
+ //
+ // A segment holds a reference to itself until it is marked for
// destruction.
+ //
+ // In addition to direct users, the MemoryManager will hold references
+ // via MappingIdentity.
refs.AtomicRefCount
mfp pgalloc.MemoryFileProvider
@@ -484,9 +517,8 @@ type AttachOpts struct {
// ConfigureAttach creates an mmap configuration for the segment with the
// requested attach options.
//
-// ConfigureAttach returns with a ref on s on success. The caller should drop
-// this once the map is installed. This reference prevents s from being
-// destroyed before the returned configuration is used.
+// Postconditions: The returned MMapOpts are valid only as long as a reference
+// continues to be held on s.
func (s *Shm) ConfigureAttach(ctx context.Context, addr usermem.Addr, opts AttachOpts) (memmap.MMapOpts, error) {
s.mu.Lock()
defer s.mu.Unlock()
@@ -504,7 +536,6 @@ func (s *Shm) ConfigureAttach(ctx context.Context, addr usermem.Addr, opts Attac
// in the user namespace that governs its IPC namespace." - man shmat(2)
return memmap.MMapOpts{}, syserror.EACCES
}
- s.IncRef()
return memmap.MMapOpts{
Length: s.size,
Offset: 0,
@@ -549,10 +580,15 @@ func (s *Shm) IPCStat(ctx context.Context) (*linux.ShmidDS, error) {
}
creds := auth.CredentialsFromContext(ctx)
- nattach := uint64(s.ReadRefs())
- // Don't report the self-reference we keep prior to being marked for
- // destruction. However, also don't report a count of -1 for segments marked
- // as destroyed, with no mappings.
+ // Use the reference count as a rudimentary count of the number of
+ // attaches. We exclude:
+ //
+ // 1. The reference the caller holds.
+ // 2. The self-reference held by s prior to destruction.
+ //
+ // Note that this may still overcount by including transient references
+ // used in concurrent calls.
+ nattach := uint64(s.ReadRefs()) - 1
if !s.pendingDestruction {
nattach--
}
@@ -620,18 +656,17 @@ func (s *Shm) MarkDestroyed() {
s.registry.dissociateKey(s)
s.mu.Lock()
- // Only drop the segment's self-reference once, when destruction is
- // requested. Otherwise, repeated calls to shmctl(IPC_RMID) would force a
- // segment to be destroyed prematurely, potentially with active maps to the
- // segment's address range. Remaining references are dropped when the
- // segment is detached or unmaped.
+ defer s.mu.Unlock()
if !s.pendingDestruction {
s.pendingDestruction = true
- s.mu.Unlock() // Must release s.mu before calling s.DecRef.
+ // Drop the self-reference so destruction occurs when all
+ // external references are gone.
+ //
+ // N.B. This cannot be the final DecRef, as the caller also
+ // holds a reference.
s.DecRef()
return
}
- s.mu.Unlock()
}
// checkOwnership verifies whether a segment may be accessed by ctx as an
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index ab0c6c4aa..d25a7903b 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -489,18 +489,43 @@ type Task struct {
// netns is protected by mu. netns is owned by the task goroutine.
netns bool
- // If rseqPreempted is true, before the next call to p.Switch(), interrupt
- // RSEQ critical regions as defined by tg.rseq and write the task
- // goroutine's CPU number to rseqCPUAddr. rseqCPU is the last CPU number
- // written to rseqCPUAddr.
+ // If rseqPreempted is true, before the next call to p.Switch(),
+ // interrupt rseq critical regions as defined by rseqAddr and
+ // tg.oldRSeqCritical and write the task goroutine's CPU number to
+ // rseqAddr/oldRSeqCPUAddr.
//
- // If rseqCPUAddr is 0, rseqCPU is -1.
+ // We support two ABIs for restartable sequences:
//
- // rseqCPUAddr, rseqCPU, and rseqPreempted are exclusive to the task
- // goroutine.
+ // 1. The upstream interface added in v4.18,
+ // 2. An "old" interface never merged upstream. In the implementation,
+ // this is referred to as "old rseq".
+ //
+ // rseqPreempted is exclusive to the task goroutine.
rseqPreempted bool `state:"nosave"`
- rseqCPUAddr usermem.Addr
- rseqCPU int32
+
+ // rseqCPU is the last CPU number written to rseqAddr/oldRSeqCPUAddr.
+ //
+ // If rseq is unused, rseqCPU is -1 for convenient use in
+ // platform.Context.Switch.
+ //
+ // rseqCPU is exclusive to the task goroutine.
+ rseqCPU int32
+
+ // oldRSeqCPUAddr is a pointer to the userspace old rseq CPU variable.
+ //
+ // oldRSeqCPUAddr is exclusive to the task goroutine.
+ oldRSeqCPUAddr usermem.Addr
+
+ // rseqAddr is a pointer to the userspace linux.RSeq structure.
+ //
+ // rseqAddr is exclusive to the task goroutine.
+ rseqAddr usermem.Addr
+
+ // rseqSignature is the signature that the rseq abort IP must be signed
+ // with.
+ //
+ // rseqSignature is exclusive to the task goroutine.
+ rseqSignature uint32
// copyScratchBuffer is a buffer available to CopyIn/CopyOut
// implementations that require an intermediate buffer to copy data
diff --git a/pkg/sentry/kernel/task_clone.go b/pkg/sentry/kernel/task_clone.go
index 5f3589493..247bd4aba 100644
--- a/pkg/sentry/kernel/task_clone.go
+++ b/pkg/sentry/kernel/task_clone.go
@@ -236,7 +236,10 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
} else if opts.NewPIDNamespace {
pidns = pidns.NewChild(userns)
}
+
tg := t.tg
+ rseqAddr := usermem.Addr(0)
+ rseqSignature := uint32(0)
if opts.NewThreadGroup {
tg.mounts.IncRef()
sh := t.tg.signalHandlers
@@ -244,6 +247,8 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
sh = sh.Fork()
}
tg = t.k.NewThreadGroup(tg.mounts, pidns, sh, opts.TerminationSignal, tg.limits.GetCopy())
+ rseqAddr = t.rseqAddr
+ rseqSignature = t.rseqSignature
}
cfg := &TaskConfig{
@@ -260,6 +265,8 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
UTSNamespace: utsns,
IPCNamespace: ipcns,
AbstractSocketNamespace: t.abstractSockets,
+ RSeqAddr: rseqAddr,
+ RSeqSignature: rseqSignature,
ContainerID: t.ContainerID(),
}
if opts.NewThreadGroup {
diff --git a/pkg/sentry/kernel/task_exec.go b/pkg/sentry/kernel/task_exec.go
index 90a6190f1..fa6528386 100644
--- a/pkg/sentry/kernel/task_exec.go
+++ b/pkg/sentry/kernel/task_exec.go
@@ -190,9 +190,11 @@ func (r *runSyscallAfterExecStop) execute(t *Task) taskRunState {
t.updateRSSLocked()
// Restartable sequence state is discarded.
t.rseqPreempted = false
- t.rseqCPUAddr = 0
t.rseqCPU = -1
- t.tg.rscr.Store(&RSEQCriticalRegion{})
+ t.rseqAddr = 0
+ t.rseqSignature = 0
+ t.oldRSeqCPUAddr = 0
+ t.tg.oldRSeqCritical.Store(&OldRSeqCriticalRegion{})
t.tg.pidns.owner.mu.Unlock()
// Remove FDs with the CloseOnExec flag set.
diff --git a/pkg/sentry/kernel/task_run.go b/pkg/sentry/kernel/task_run.go
index d97f8c189..6357273d3 100644
--- a/pkg/sentry/kernel/task_run.go
+++ b/pkg/sentry/kernel/task_run.go
@@ -169,12 +169,22 @@ func (*runApp) execute(t *Task) taskRunState {
// Apply restartable sequences.
if t.rseqPreempted {
t.rseqPreempted = false
- if t.rseqCPUAddr != 0 {
+ if t.rseqAddr != 0 || t.oldRSeqCPUAddr != 0 {
+ // Linux writes the CPU on every preemption. We only do
+ // so if it changed. Thus we may delay delivery of
+ // SIGSEGV if rseqAddr/oldRSeqCPUAddr is invalid.
cpu := int32(hostcpu.GetCPU())
if t.rseqCPU != cpu {
t.rseqCPU = cpu
if err := t.rseqCopyOutCPU(); err != nil {
- t.Warningf("Failed to copy CPU to %#x for RSEQ: %v", t.rseqCPUAddr, err)
+ t.Debugf("Failed to copy CPU to %#x for rseq: %v", t.rseqAddr, err)
+ t.forceSignal(linux.SIGSEGV, false)
+ t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
+ // Re-enter the task run loop for signal delivery.
+ return (*runApp)(nil)
+ }
+ if err := t.oldRSeqCopyOutCPU(); err != nil {
+ t.Debugf("Failed to copy CPU to %#x for old rseq: %v", t.oldRSeqCPUAddr, err)
t.forceSignal(linux.SIGSEGV, false)
t.SendSignal(SignalInfoPriv(linux.SIGSEGV))
// Re-enter the task run loop for signal delivery.
@@ -320,7 +330,7 @@ func (*runApp) execute(t *Task) taskRunState {
return (*runApp)(nil)
case platform.ErrContextCPUPreempted:
- // Ensure that RSEQ critical sections are interrupted and per-thread
+ // Ensure that rseq critical sections are interrupted and per-thread
// CPU values are updated before the next platform.Context.Switch().
t.rseqPreempted = true
return (*runApp)(nil)
diff --git a/pkg/sentry/kernel/task_start.go b/pkg/sentry/kernel/task_start.go
index 3522a4ae5..58af16ee2 100644
--- a/pkg/sentry/kernel/task_start.go
+++ b/pkg/sentry/kernel/task_start.go
@@ -21,6 +21,7 @@ import (
"gvisor.dev/gvisor/pkg/sentry/kernel/futex"
"gvisor.dev/gvisor/pkg/sentry/kernel/sched"
"gvisor.dev/gvisor/pkg/sentry/usage"
+ "gvisor.dev/gvisor/pkg/sentry/usermem"
"gvisor.dev/gvisor/pkg/syserror"
)
@@ -79,6 +80,13 @@ type TaskConfig struct {
// AbstractSocketNamespace is the AbstractSocketNamespace of the new task.
AbstractSocketNamespace *AbstractSocketNamespace
+ // RSeqAddr is a pointer to the the userspace linux.RSeq structure.
+ RSeqAddr usermem.Addr
+
+ // RSeqSignature is the signature that the rseq abort IP must be signed
+ // with.
+ RSeqSignature uint32
+
// ContainerID is the container the new task belongs to.
ContainerID string
}
@@ -126,6 +134,8 @@ func (ts *TaskSet) newTask(cfg *TaskConfig) (*Task, error) {
ipcns: cfg.IPCNamespace,
abstractSockets: cfg.AbstractSocketNamespace,
rseqCPU: -1,
+ rseqAddr: cfg.RSeqAddr,
+ rseqSignature: cfg.RSeqSignature,
futexWaiter: futex.NewWaiter(),
containerID: cfg.ContainerID,
}
diff --git a/pkg/sentry/kernel/thread_group.go b/pkg/sentry/kernel/thread_group.go
index 0cded73f6..c0197a563 100644
--- a/pkg/sentry/kernel/thread_group.go
+++ b/pkg/sentry/kernel/thread_group.go
@@ -238,8 +238,8 @@ type ThreadGroup struct {
// execed is protected by the TaskSet mutex.
execed bool
- // rscr is the thread group's RSEQ critical region.
- rscr atomic.Value `state:".(*RSEQCriticalRegion)"`
+ // oldRSeqCritical is the thread group's old rseq critical region.
+ oldRSeqCritical atomic.Value `state:".(*OldRSeqCriticalRegion)"`
// mounts is the thread group's mount namespace. This does not really
// correspond to a "mount namespace" in Linux, but is more like a
@@ -273,18 +273,18 @@ func (k *Kernel) NewThreadGroup(mntns *fs.MountNamespace, pidns *PIDNamespace, s
}
tg.itimerRealTimer = ktime.NewTimer(k.monotonicClock, &itimerRealListener{tg: tg})
tg.timers = make(map[linux.TimerID]*IntervalTimer)
- tg.rscr.Store(&RSEQCriticalRegion{})
+ tg.oldRSeqCritical.Store(&OldRSeqCriticalRegion{})
return tg
}
-// saveRscr is invoked by stateify.
-func (tg *ThreadGroup) saveRscr() *RSEQCriticalRegion {
- return tg.rscr.Load().(*RSEQCriticalRegion)
+// saveOldRSeqCritical is invoked by stateify.
+func (tg *ThreadGroup) saveOldRSeqCritical() *OldRSeqCriticalRegion {
+ return tg.oldRSeqCritical.Load().(*OldRSeqCriticalRegion)
}
-// loadRscr is invoked by stateify.
-func (tg *ThreadGroup) loadRscr(rscr *RSEQCriticalRegion) {
- tg.rscr.Store(rscr)
+// loadOldRSeqCritical is invoked by stateify.
+func (tg *ThreadGroup) loadOldRSeqCritical(r *OldRSeqCriticalRegion) {
+ tg.oldRSeqCritical.Store(r)
}
// SignalHandlers returns the signal handlers used by tg.
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-29 09:43:02 +0000