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Resolve issue with file mode for host fds.

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Instead of plumbing error through kernfs.Inode.Mode, panic if err != nil.
The errors that can result from an fstat syscall all indicate that something
is fundamentally wrong, and panicking should be acceptable.

PiperOrigin-RevId: 307406847
This commit is contained in:
Dean Deng
2020-04-20 08:51:47 -07:00
committed by gVisor bot
parent db2a60be67
commit 1a940f2b6c
1 changed files with 3 additions and 31 deletions
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pkg/sentry/fsimpl/host/host.go
+3 -31
View File
@@ -94,7 +94,6 @@ func ImportFD(mnt *vfs.Mount, hostFD int, isTTY bool) (*vfs.FileDescription, err
isTTY: isTTY,
canMap: canMap(uint32(fileType)),
ino: fs.NextIno(),
mode: fileMode,
// For simplicity, set offset to 0. Technically, we should use the existing
// offset on the host if the file is seekable.
offset: 0,
@@ -149,20 +148,6 @@ type inode struct {
// This field is initialized at creation time and is immutable.
ino uint64
// modeMu protects mode.
modeMu sync.Mutex
// mode is a cached version of the file mode on the host. Note that it may
// become out of date if the mode is changed on the host, e.g. with chmod.
//
// Generally, it is better to retrieve the mode from the host through an
// fstat syscall. We only use this value in inode.Mode(), which cannot
// return an error, if the syscall to host fails.
//
// FIXME(b/152294168): Plumb error into Inode.Mode() return value so we
// can get rid of this.
mode linux.FileMode
// offsetMu protects offset.
offsetMu sync.Mutex
@@ -195,10 +180,11 @@ func (i *inode) CheckPermissions(ctx context.Context, creds *auth.Credentials, a
// Mode implements kernfs.Inode.
func (i *inode) Mode() linux.FileMode {
mode, _, _, err := i.getPermissions()
// Retrieving the mode from the host fd using fstat(2) should not fail.
// If the syscall does not succeed, something is fundamentally wrong.
if err != nil {
return i.mode
panic(fmt.Sprintf("failed to retrieve mode from host fd %d: %v", i.hostFD, err))
}
return linux.FileMode(mode)
}
@@ -208,11 +194,6 @@ func (i *inode) getPermissions() (linux.FileMode, auth.KUID, auth.KGID, error) {
if err := syscall.Fstat(i.hostFD, &s); err != nil {
return 0, 0, 0, err
}
// Update cached mode.
i.modeMu.Lock()
i.mode = linux.FileMode(s.Mode)
i.modeMu.Unlock()
return linux.FileMode(s.Mode), auth.KUID(s.Uid), auth.KGID(s.Gid), nil
}
@@ -292,12 +273,6 @@ func (i *inode) Stat(_ *vfs.Filesystem, opts vfs.StatOptions) (linux.Statx, erro
ls.Ino = i.ino
}
// Update cached mode.
if (mask&linux.STATX_TYPE != 0) && (mask&linux.STATX_MODE != 0) {
i.modeMu.Lock()
i.mode = linux.FileMode(s.Mode)
i.modeMu.Unlock()
}
return ls, nil
}
@@ -364,9 +339,6 @@ func (i *inode) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Cre
if err := syscall.Fchmod(i.hostFD, uint32(s.Mode)); err != nil {
return err
}
i.modeMu.Lock()
i.mode = linux.FileMode(s.Mode)
i.modeMu.Unlock()
}
if m&linux.STATX_SIZE != 0 {
if err := syscall.Ftruncate(i.hostFD, int64(s.Size)); err != nil {