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-rwxr-xr-xpkg/sentry/vfs/file_description.go141
1 files changed, 96 insertions, 45 deletions
diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index c5a9adca3..df03886c3 100755
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -20,6 +20,7 @@ import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/context"
+ "gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/sentry/usermem"
"gvisor.dev/gvisor/pkg/syserror"
@@ -39,49 +40,43 @@ type FileDescription struct {
// operations.
refs int64
+ // statusFlags contains status flags, "initialized by open(2) and possibly
+ // modified by fcntl()" - fcntl(2). statusFlags is accessed using atomic
+ // memory operations.
+ statusFlags uint32
+
// vd is the filesystem location at which this FileDescription was opened.
// A reference is held on vd. vd is immutable.
vd VirtualDentry
+ opts FileDescriptionOptions
+
// impl is the FileDescriptionImpl associated with this Filesystem. impl is
// immutable. This should be the last field in FileDescription.
impl FileDescriptionImpl
}
+// FileDescriptionOptions contains options to FileDescription.Init().
+type FileDescriptionOptions struct {
+ // If AllowDirectIO is true, allow O_DIRECT to be set on the file. This is
+ // usually only the case if O_DIRECT would actually have an effect.
+ AllowDirectIO bool
+}
+
// Init must be called before first use of fd. It takes ownership of references
-// on mnt and d held by the caller.
-func (fd *FileDescription) Init(impl FileDescriptionImpl, mnt *Mount, d *Dentry) {
+// on mnt and d held by the caller. statusFlags is the initial file description
+// status flags, which is usually the full set of flags passed to open(2).
+func (fd *FileDescription) Init(impl FileDescriptionImpl, statusFlags uint32, mnt *Mount, d *Dentry, opts *FileDescriptionOptions) {
fd.refs = 1
+ fd.statusFlags = statusFlags | linux.O_LARGEFILE
fd.vd = VirtualDentry{
mount: mnt,
dentry: d,
}
+ fd.opts = *opts
fd.impl = impl
}
-// Impl returns the FileDescriptionImpl associated with fd.
-func (fd *FileDescription) Impl() FileDescriptionImpl {
- return fd.impl
-}
-
-// Mount returns the mount on which fd was opened. It does not take a reference
-// on the returned Mount.
-func (fd *FileDescription) Mount() *Mount {
- return fd.vd.mount
-}
-
-// Dentry returns the dentry at which fd was opened. It does not take a
-// reference on the returned Dentry.
-func (fd *FileDescription) Dentry() *Dentry {
- return fd.vd.dentry
-}
-
-// VirtualDentry returns the location at which fd was opened. It does not take
-// a reference on the returned VirtualDentry.
-func (fd *FileDescription) VirtualDentry() VirtualDentry {
- return fd.vd
-}
-
// IncRef increments fd's reference count.
func (fd *FileDescription) IncRef() {
atomic.AddInt64(&fd.refs, 1)
@@ -113,6 +108,82 @@ func (fd *FileDescription) DecRef() {
}
}
+// Mount returns the mount on which fd was opened. It does not take a reference
+// on the returned Mount.
+func (fd *FileDescription) Mount() *Mount {
+ return fd.vd.mount
+}
+
+// Dentry returns the dentry at which fd was opened. It does not take a
+// reference on the returned Dentry.
+func (fd *FileDescription) Dentry() *Dentry {
+ return fd.vd.dentry
+}
+
+// VirtualDentry returns the location at which fd was opened. It does not take
+// a reference on the returned VirtualDentry.
+func (fd *FileDescription) VirtualDentry() VirtualDentry {
+ return fd.vd
+}
+
+// StatusFlags returns file description status flags, as for fcntl(F_GETFL).
+func (fd *FileDescription) StatusFlags() uint32 {
+ return atomic.LoadUint32(&fd.statusFlags)
+}
+
+// SetStatusFlags sets file description status flags, as for fcntl(F_SETFL).
+func (fd *FileDescription) SetStatusFlags(ctx context.Context, creds *auth.Credentials, flags uint32) error {
+ // Compare Linux's fs/fcntl.c:setfl().
+ oldFlags := fd.StatusFlags()
+ // Linux documents this check as "O_APPEND cannot be cleared if the file is
+ // marked as append-only and the file is open for write", which would make
+ // sense. However, the check as actually implemented seems to be "O_APPEND
+ // cannot be changed if the file is marked as append-only".
+ if (flags^oldFlags)&linux.O_APPEND != 0 {
+ stat, err := fd.impl.Stat(ctx, StatOptions{
+ // There is no mask bit for stx_attributes.
+ Mask: 0,
+ // Linux just reads inode::i_flags directly.
+ Sync: linux.AT_STATX_DONT_SYNC,
+ })
+ if err != nil {
+ return err
+ }
+ if (stat.AttributesMask&linux.STATX_ATTR_APPEND != 0) && (stat.Attributes&linux.STATX_ATTR_APPEND != 0) {
+ return syserror.EPERM
+ }
+ }
+ if (flags&linux.O_NOATIME != 0) && (oldFlags&linux.O_NOATIME == 0) {
+ stat, err := fd.impl.Stat(ctx, StatOptions{
+ Mask: linux.STATX_UID,
+ // Linux's inode_owner_or_capable() just reads inode::i_uid
+ // directly.
+ Sync: linux.AT_STATX_DONT_SYNC,
+ })
+ if err != nil {
+ return err
+ }
+ if stat.Mask&linux.STATX_UID == 0 {
+ return syserror.EPERM
+ }
+ if !CanActAsOwner(creds, auth.KUID(stat.UID)) {
+ return syserror.EPERM
+ }
+ }
+ if flags&linux.O_DIRECT != 0 && !fd.opts.AllowDirectIO {
+ return syserror.EINVAL
+ }
+ // TODO(jamieliu): FileDescriptionImpl.SetOAsync()?
+ const settableFlags = linux.O_APPEND | linux.O_ASYNC | linux.O_DIRECT | linux.O_NOATIME | linux.O_NONBLOCK
+ atomic.StoreUint32(&fd.statusFlags, (oldFlags&^settableFlags)|(flags&settableFlags))
+ return nil
+}
+
+// Impl returns the FileDescriptionImpl associated with fd.
+func (fd *FileDescription) Impl() FileDescriptionImpl {
+ return fd.impl
+}
+
// FileDescriptionImpl contains implementation details for an FileDescription.
// Implementations of FileDescriptionImpl should contain their associated
// FileDescription by value as their first field.
@@ -132,14 +203,6 @@ type FileDescriptionImpl interface {
// prevent the file descriptor from being closed.
OnClose(ctx context.Context) error
- // StatusFlags returns file description status flags, as for
- // fcntl(F_GETFL).
- StatusFlags(ctx context.Context) (uint32, error)
-
- // SetStatusFlags sets file description status flags, as for
- // fcntl(F_SETFL).
- SetStatusFlags(ctx context.Context, flags uint32) error
-
// Stat returns metadata for the file represented by the FileDescription.
Stat(ctx context.Context, opts StatOptions) (linux.Statx, error)
@@ -264,18 +327,6 @@ func (fd *FileDescription) OnClose(ctx context.Context) error {
return fd.impl.OnClose(ctx)
}
-// StatusFlags returns file description status flags, as for fcntl(F_GETFL).
-func (fd *FileDescription) StatusFlags(ctx context.Context) (uint32, error) {
- flags, err := fd.impl.StatusFlags(ctx)
- flags |= linux.O_LARGEFILE
- return flags, err
-}
-
-// SetStatusFlags sets file description status flags, as for fcntl(F_SETFL).
-func (fd *FileDescription) SetStatusFlags(ctx context.Context, flags uint32) error {
- return fd.impl.SetStatusFlags(ctx, flags)
-}
-
// Stat returns metadata for the file represented by fd.
func (fd *FileDescription) Stat(ctx context.Context, opts StatOptions) (linux.Statx, error) {
return fd.impl.Stat(ctx, opts)