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-rw-r--r--pkg/sentry/fsimpl/tmpfs/filesystem.go8
-rw-r--r--pkg/sentry/fsimpl/tmpfs/regular_file.go233
-rw-r--r--pkg/sentry/fsimpl/tmpfs/tmpfs.go16
3 files changed, 213 insertions, 44 deletions
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 7f7b791c4..e1b551422 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -16,7 +16,6 @@ package tmpfs
import (
"fmt"
- "sync/atomic"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
@@ -347,10 +346,9 @@ func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, opts *vfs.Open
return nil, err
}
if opts.Flags&linux.O_TRUNC != 0 {
- impl.mu.Lock()
- impl.data.Truncate(0, impl.memFile)
- atomic.StoreUint64(&impl.size, 0)
- impl.mu.Unlock()
+ if _, err := impl.truncate(0); err != nil {
+ return nil, err
+ }
}
return &fd.vfsfd, nil
case *directory:
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file.go b/pkg/sentry/fsimpl/tmpfs/regular_file.go
index dab346a41..711442424 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file.go
@@ -15,6 +15,7 @@
package tmpfs
import (
+ "fmt"
"io"
"math"
"sync/atomic"
@@ -22,6 +23,7 @@ import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/safemem"
+ "gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
"gvisor.dev/gvisor/pkg/sentry/fs/lock"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
@@ -34,25 +36,53 @@ import (
"gvisor.dev/gvisor/pkg/usermem"
)
+// regularFile is a regular (=S_IFREG) tmpfs file.
type regularFile struct {
inode inode
// memFile is a platform.File used to allocate pages to this regularFile.
memFile *pgalloc.MemoryFile
- // mu protects the fields below.
- mu sync.RWMutex
+ // mapsMu protects mappings.
+ mapsMu sync.Mutex `state:"nosave"`
+
+ // mappings tracks mappings of the file into memmap.MappingSpaces.
+ //
+ // Protected by mapsMu.
+ mappings memmap.MappingSet
+
+ // writableMappingPages tracks how many pages of virtual memory are mapped
+ // as potentially writable from this file. If a page has multiple mappings,
+ // each mapping is counted separately.
+ //
+ // This counter is susceptible to overflow as we can potentially count
+ // mappings from many VMAs. We count pages rather than bytes to slightly
+ // mitigate this.
+ //
+ // Protected by mapsMu.
+ writableMappingPages uint64
+
+ // dataMu protects the fields below.
+ dataMu sync.RWMutex
// data maps offsets into the file to offsets into memFile that store
// the file's data.
+ //
+ // Protected by dataMu.
data fsutil.FileRangeSet
- // size is the size of data, but accessed using atomic memory
- // operations to avoid locking in inode.stat().
- size uint64
-
// seals represents file seals on this inode.
+ //
+ // Protected by dataMu.
seals uint32
+
+ // size is the size of data.
+ //
+ // Protected by both dataMu and inode.mu; reading it requires holding
+ // either mutex, while writing requires holding both AND using atomics.
+ // Readers that do not require consistency (like Stat) may read the
+ // value atomically without holding either lock.
+ size uint64
}
func (fs *filesystem) newRegularFile(creds *auth.Credentials, mode linux.FileMode) *inode {
@@ -66,39 +96,170 @@ func (fs *filesystem) newRegularFile(creds *auth.Credentials, mode linux.FileMod
// truncate grows or shrinks the file to the given size. It returns true if the
// file size was updated.
-func (rf *regularFile) truncate(size uint64) (bool, error) {
- rf.mu.Lock()
- defer rf.mu.Unlock()
+func (rf *regularFile) truncate(newSize uint64) (bool, error) {
+ rf.inode.mu.Lock()
+ defer rf.inode.mu.Unlock()
+ return rf.truncateLocked(newSize)
+}
- if size == rf.size {
+// Preconditions: rf.inode.mu must be held.
+func (rf *regularFile) truncateLocked(newSize uint64) (bool, error) {
+ oldSize := rf.size
+ if newSize == oldSize {
// Nothing to do.
return false, nil
}
- if size > rf.size {
- // Growing the file.
+ // Need to hold inode.mu and dataMu while modifying size.
+ rf.dataMu.Lock()
+ if newSize > oldSize {
+ // Can we grow the file?
if rf.seals&linux.F_SEAL_GROW != 0 {
- // Seal does not allow growth.
+ rf.dataMu.Unlock()
return false, syserror.EPERM
}
- rf.size = size
+ // We only need to update the file size.
+ atomic.StoreUint64(&rf.size, newSize)
+ rf.dataMu.Unlock()
return true, nil
}
- // Shrinking the file
+ // We are shrinking the file. First check if this is allowed.
if rf.seals&linux.F_SEAL_SHRINK != 0 {
- // Seal does not allow shrink.
+ rf.dataMu.Unlock()
return false, syserror.EPERM
}
- // TODO(gvisor.dev/issues/1197): Invalidate mappings once we have
- // mappings.
+ // Update the file size.
+ atomic.StoreUint64(&rf.size, newSize)
+ rf.dataMu.Unlock()
+
+ // Invalidate past translations of truncated pages.
+ oldpgend := fs.OffsetPageEnd(int64(oldSize))
+ newpgend := fs.OffsetPageEnd(int64(newSize))
+ if newpgend < oldpgend {
+ rf.mapsMu.Lock()
+ rf.mappings.Invalidate(memmap.MappableRange{newpgend, oldpgend}, memmap.InvalidateOpts{
+ // Compare Linux's mm/shmem.c:shmem_setattr() =>
+ // mm/memory.c:unmap_mapping_range(evencows=1).
+ InvalidatePrivate: true,
+ })
+ rf.mapsMu.Unlock()
+ }
- rf.data.Truncate(size, rf.memFile)
- rf.size = size
+ // We are now guaranteed that there are no translations of truncated pages,
+ // and can remove them.
+ rf.dataMu.Lock()
+ rf.data.Truncate(newSize, rf.memFile)
+ rf.dataMu.Unlock()
return true, nil
}
+// AddMapping implements memmap.Mappable.AddMapping.
+func (rf *regularFile) AddMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) error {
+ rf.mapsMu.Lock()
+ defer rf.mapsMu.Unlock()
+ rf.dataMu.RLock()
+ defer rf.dataMu.RUnlock()
+
+ // Reject writable mapping if F_SEAL_WRITE is set.
+ if rf.seals&linux.F_SEAL_WRITE != 0 && writable {
+ return syserror.EPERM
+ }
+
+ rf.mappings.AddMapping(ms, ar, offset, writable)
+ if writable {
+ pagesBefore := rf.writableMappingPages
+
+ // ar is guaranteed to be page aligned per memmap.Mappable.
+ rf.writableMappingPages += uint64(ar.Length() / usermem.PageSize)
+
+ if rf.writableMappingPages < pagesBefore {
+ panic(fmt.Sprintf("Overflow while mapping potentially writable pages pointing to a tmpfs file. Before %v, after %v", pagesBefore, rf.writableMappingPages))
+ }
+ }
+
+ return nil
+}
+
+// RemoveMapping implements memmap.Mappable.RemoveMapping.
+func (rf *regularFile) RemoveMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) {
+ rf.mapsMu.Lock()
+ defer rf.mapsMu.Unlock()
+
+ rf.mappings.RemoveMapping(ms, ar, offset, writable)
+
+ if writable {
+ pagesBefore := rf.writableMappingPages
+
+ // ar is guaranteed to be page aligned per memmap.Mappable.
+ rf.writableMappingPages -= uint64(ar.Length() / usermem.PageSize)
+
+ if rf.writableMappingPages > pagesBefore {
+ panic(fmt.Sprintf("Underflow while unmapping potentially writable pages pointing to a tmpfs file. Before %v, after %v", pagesBefore, rf.writableMappingPages))
+ }
+ }
+}
+
+// CopyMapping implements memmap.Mappable.CopyMapping.
+func (rf *regularFile) CopyMapping(ctx context.Context, ms memmap.MappingSpace, srcAR, dstAR usermem.AddrRange, offset uint64, writable bool) error {
+ return rf.AddMapping(ctx, ms, dstAR, offset, writable)
+}
+
+// Translate implements memmap.Mappable.Translate.
+func (rf *regularFile) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
+ rf.dataMu.Lock()
+ defer rf.dataMu.Unlock()
+
+ // Constrain translations to f.attr.Size (rounded up) to prevent
+ // translation to pages that may be concurrently truncated.
+ pgend := fs.OffsetPageEnd(int64(rf.size))
+ var beyondEOF bool
+ if required.End > pgend {
+ if required.Start >= pgend {
+ return nil, &memmap.BusError{io.EOF}
+ }
+ beyondEOF = true
+ required.End = pgend
+ }
+ if optional.End > pgend {
+ optional.End = pgend
+ }
+
+ cerr := rf.data.Fill(ctx, required, optional, rf.memFile, usage.Tmpfs, func(_ context.Context, dsts safemem.BlockSeq, _ uint64) (uint64, error) {
+ // Newly-allocated pages are zeroed, so we don't need to do anything.
+ return dsts.NumBytes(), nil
+ })
+
+ var ts []memmap.Translation
+ var translatedEnd uint64
+ for seg := rf.data.FindSegment(required.Start); seg.Ok() && seg.Start() < required.End; seg, _ = seg.NextNonEmpty() {
+ segMR := seg.Range().Intersect(optional)
+ ts = append(ts, memmap.Translation{
+ Source: segMR,
+ File: rf.memFile,
+ Offset: seg.FileRangeOf(segMR).Start,
+ Perms: usermem.AnyAccess,
+ })
+ translatedEnd = segMR.End
+ }
+
+ // Don't return the error returned by f.data.Fill if it occurred outside of
+ // required.
+ if translatedEnd < required.End && cerr != nil {
+ return ts, &memmap.BusError{cerr}
+ }
+ if beyondEOF {
+ return ts, &memmap.BusError{io.EOF}
+ }
+ return ts, nil
+}
+
+// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
+func (*regularFile) InvalidateUnsavable(context.Context) error {
+ return nil
+}
+
type regularFileFD struct {
fileDescription
@@ -152,8 +313,10 @@ func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, off
// Overflow.
return 0, syserror.EFBIG
}
+ f.inode.mu.Lock()
rw := getRegularFileReadWriter(f, offset)
n, err := src.CopyInTo(ctx, rw)
+ f.inode.mu.Unlock()
putRegularFileReadWriter(rw)
return n, err
}
@@ -215,6 +378,12 @@ func (fd *regularFileFD) UnlockPOSIX(ctx context.Context, uid lock.UniqueID, rng
return nil
}
+// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
+func (fd *regularFileFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
+ file := fd.inode().impl.(*regularFile)
+ return vfs.GenericConfigureMMap(&fd.vfsfd, file, opts)
+}
+
// regularFileReadWriter implements safemem.Reader and Safemem.Writer.
type regularFileReadWriter struct {
file *regularFile
@@ -244,14 +413,15 @@ func putRegularFileReadWriter(rw *regularFileReadWriter) {
// ReadToBlocks implements safemem.Reader.ReadToBlocks.
func (rw *regularFileReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
- rw.file.mu.RLock()
+ rw.file.dataMu.RLock()
+ defer rw.file.dataMu.RUnlock()
+ size := rw.file.size
// Compute the range to read (limited by file size and overflow-checked).
- if rw.off >= rw.file.size {
- rw.file.mu.RUnlock()
+ if rw.off >= size {
return 0, io.EOF
}
- end := rw.file.size
+ end := size
if rend := rw.off + dsts.NumBytes(); rend > rw.off && rend < end {
end = rend
}
@@ -265,7 +435,6 @@ func (rw *regularFileReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, er
// Get internal mappings.
ims, err := rw.file.memFile.MapInternal(seg.FileRangeOf(seg.Range().Intersect(mr)), usermem.Read)
if err != nil {
- rw.file.mu.RUnlock()
return done, err
}
@@ -275,7 +444,6 @@ func (rw *regularFileReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, er
rw.off += uint64(n)
dsts = dsts.DropFirst64(n)
if err != nil {
- rw.file.mu.RUnlock()
return done, err
}
@@ -291,7 +459,6 @@ func (rw *regularFileReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, er
rw.off += uint64(n)
dsts = dsts.DropFirst64(n)
if err != nil {
- rw.file.mu.RUnlock()
return done, err
}
@@ -299,13 +466,16 @@ func (rw *regularFileReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, er
seg, gap = gap.NextSegment(), fsutil.FileRangeGapIterator{}
}
}
- rw.file.mu.RUnlock()
return done, nil
}
// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
+//
+// Preconditions: inode.mu must be held.
func (rw *regularFileReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
- rw.file.mu.Lock()
+ // Hold dataMu so we can modify size.
+ rw.file.dataMu.Lock()
+ defer rw.file.dataMu.Unlock()
// Compute the range to write (overflow-checked).
end := rw.off + srcs.NumBytes()
@@ -316,7 +486,6 @@ func (rw *regularFileReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64,
// Check if seals prevent either file growth or all writes.
switch {
case rw.file.seals&linux.F_SEAL_WRITE != 0: // Write sealed
- rw.file.mu.Unlock()
return 0, syserror.EPERM
case end > rw.file.size && rw.file.seals&linux.F_SEAL_GROW != 0: // Grow sealed
// When growth is sealed, Linux effectively allows writes which would
@@ -338,7 +507,6 @@ func (rw *regularFileReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64,
}
if end <= rw.off {
// Truncation would result in no data being written.
- rw.file.mu.Unlock()
return 0, syserror.EPERM
}
}
@@ -395,9 +563,8 @@ exitLoop:
// If the write ends beyond the file's previous size, it causes the
// file to grow.
if rw.off > rw.file.size {
- atomic.StoreUint64(&rw.file.size, rw.off)
+ rw.file.size = rw.off
}
- rw.file.mu.Unlock()
return done, retErr
}
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index c5bb17562..521206305 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -18,9 +18,10 @@
// Lock order:
//
// filesystem.mu
-// regularFileFD.offMu
-// regularFile.mu
// inode.mu
+// regularFileFD.offMu
+// regularFile.mapsMu
+// regularFile.dataMu
package tmpfs
import (
@@ -226,12 +227,15 @@ func (i *inode) tryIncRef() bool {
func (i *inode) decRef() {
if refs := atomic.AddInt64(&i.refs, -1); refs == 0 {
- // This is unnecessary; it's mostly to simulate what tmpfs would do.
if regFile, ok := i.impl.(*regularFile); ok {
- regFile.mu.Lock()
+ // Hold inode.mu and regFile.dataMu while mutating
+ // size.
+ i.mu.Lock()
+ regFile.dataMu.Lock()
regFile.data.DropAll(regFile.memFile)
atomic.StoreUint64(&regFile.size, 0)
- regFile.mu.Unlock()
+ regFile.dataMu.Unlock()
+ i.mu.Unlock()
}
} else if refs < 0 {
panic("tmpfs.inode.decRef() called without holding a reference")
@@ -320,7 +324,7 @@ func (i *inode) setStat(stat linux.Statx) error {
if mask&linux.STATX_SIZE != 0 {
switch impl := i.impl.(type) {
case *regularFile:
- updated, err := impl.truncate(stat.Size)
+ updated, err := impl.truncateLocked(stat.Size)
if err != nil {
return err
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-02 03:26:13 +0000