Fix panic when calling dup2().

PiperOrigin-RevId: 329572337

10 files changed, 49 insertions, 45 deletions

diff --git a/pkg/sentry/kernel/fd_table.go b/pkg/sentry/kernel/fd_table.go
index 5773244ac..89223fa36 100644
--- a/pkg/sentry/kernel/fd_table.go
+++ b/pkg/sentry/kernel/fd_table.go
@@ -112,7 +112,7 @@ func (f *FDTable) loadDescriptorTable(m map[int32]descriptor) {
 	ctx := context.Background()
 	f.init() // Initialize table.
 	for fd, d := range m {
-		f.setAll(fd, d.file, d.fileVFS2, d.flags)
+		f.setAll(ctx, fd, d.file, d.fileVFS2, d.flags)
 
 		// Note that we do _not_ need to acquire a extra table reference here. The
 		// table reference will already be accounted for in the file, so we drop the
@@ -127,7 +127,7 @@ func (f *FDTable) loadDescriptorTable(m map[int32]descriptor) {
 }
 
 // drop drops the table reference.
-func (f *FDTable) drop(file *fs.File) {
+func (f *FDTable) drop(ctx context.Context, file *fs.File) {
 	// Release locks.
 	file.Dirent.Inode.LockCtx.Posix.UnlockRegion(f, lock.LockRange{0, lock.LockEOF})
 
@@ -145,14 +145,13 @@ func (f *FDTable) drop(file *fs.File) {
 	d.InotifyEvent(ev, 0)
 
 	// Drop the table reference.
-	file.DecRef(context.Background())
+	file.DecRef(ctx)
 }
 
 // dropVFS2 drops the table reference.
-func (f *FDTable) dropVFS2(file *vfs.FileDescription) {
+func (f *FDTable) dropVFS2(ctx context.Context, file *vfs.FileDescription) {
 	// Release any POSIX lock possibly held by the FDTable. Range {0, 0} means the
 	// entire file.
-	ctx := context.Background()
 	err := file.UnlockPOSIX(ctx, f, 0, 0, linux.SEEK_SET)
 	if err != nil && err != syserror.ENOLCK {
 		panic(fmt.Sprintf("UnlockPOSIX failed: %v", err))
@@ -289,15 +288,15 @@ func (f *FDTable) NewFDs(ctx context.Context, fd int32, files []*fs.File, flags
 	// Install all entries.
 	for i := fd; i < end && len(fds) < len(files); i++ {
 		if d, _, _ := f.get(i); d == nil {
-			f.set(i, files[len(fds)], flags) // Set the descriptor.
-			fds = append(fds, i)             // Record the file descriptor.
+			f.set(ctx, i, files[len(fds)], flags) // Set the descriptor.
+			fds = append(fds, i)                  // Record the file descriptor.
 		}
 	}
 
 	// Failure? Unwind existing FDs.
 	if len(fds) < len(files) {
 		for _, i := range fds {
-			f.set(i, nil, FDFlags{}) // Zap entry.
+			f.set(ctx, i, nil, FDFlags{}) // Zap entry.
 		}
 		return nil, syscall.EMFILE
 	}
@@ -344,15 +343,15 @@ func (f *FDTable) NewFDsVFS2(ctx context.Context, fd int32, files []*vfs.FileDes
 	// Install all entries.
 	for i := fd; i < end && len(fds) < len(files); i++ {
 		if d, _, _ := f.getVFS2(i); d == nil {
-			f.setVFS2(i, files[len(fds)], flags) // Set the descriptor.
-			fds = append(fds, i)                 // Record the file descriptor.
+			f.setVFS2(ctx, i, files[len(fds)], flags) // Set the descriptor.
+			fds = append(fds, i)                      // Record the file descriptor.
 		}
 	}
 
 	// Failure? Unwind existing FDs.
 	if len(fds) < len(files) {
 		for _, i := range fds {
-			f.setVFS2(i, nil, FDFlags{}) // Zap entry.
+			f.setVFS2(ctx, i, nil, FDFlags{}) // Zap entry.
 		}
 		return nil, syscall.EMFILE
 	}
@@ -397,7 +396,7 @@ func (f *FDTable) NewFDVFS2(ctx context.Context, minfd int32, file *vfs.FileDesc
 	}
 	for fd < end {
 		if d, _, _ := f.getVFS2(fd); d == nil {
-			f.setVFS2(fd, file, flags)
+			f.setVFS2(ctx, fd, file, flags)
 			if fd == f.next {
 				// Update next search start position.
 				f.next = fd + 1
@@ -439,14 +438,14 @@ func (f *FDTable) newFDAt(ctx context.Context, fd int32, file *fs.File, fileVFS2
 	// Install the entry.
 	f.mu.Lock()
 	defer f.mu.Unlock()
-	f.setAll(fd, file, fileVFS2, flags)
+	f.setAll(ctx, fd, file, fileVFS2, flags)
 	return nil
 }
 
 // SetFlags sets the flags for the given file descriptor.
 //
 // True is returned iff flags were changed.
-func (f *FDTable) SetFlags(fd int32, flags FDFlags) error {
+func (f *FDTable) SetFlags(ctx context.Context, fd int32, flags FDFlags) error {
 	if fd < 0 {
 		// Don't accept negative FDs.
 		return syscall.EBADF
@@ -462,14 +461,14 @@ func (f *FDTable) SetFlags(fd int32, flags FDFlags) error {
 	}
 
 	// Update the flags.
-	f.set(fd, file, flags)
+	f.set(ctx, fd, file, flags)
 	return nil
 }
 
 // SetFlagsVFS2 sets the flags for the given file descriptor.
 //
 // True is returned iff flags were changed.
-func (f *FDTable) SetFlagsVFS2(fd int32, flags FDFlags) error {
+func (f *FDTable) SetFlagsVFS2(ctx context.Context, fd int32, flags FDFlags) error {
 	if fd < 0 {
 		// Don't accept negative FDs.
 		return syscall.EBADF
@@ -485,7 +484,7 @@ func (f *FDTable) SetFlagsVFS2(fd int32, flags FDFlags) error {
 	}
 
 	// Update the flags.
-	f.setVFS2(fd, file, flags)
+	f.setVFS2(ctx, fd, file, flags)
 	return nil
 }
 
@@ -584,9 +583,9 @@ func (f *FDTable) Fork(ctx context.Context) *FDTable {
 		// reference for the clone. We don't need anything else.
 		switch {
 		case file != nil:
-			clone.set(fd, file, flags)
+			clone.set(ctx, fd, file, flags)
 		case fileVFS2 != nil:
-			clone.setVFS2(fd, fileVFS2, flags)
+			clone.setVFS2(ctx, fd, fileVFS2, flags)
 		}
 	})
 	return clone
@@ -595,7 +594,7 @@ func (f *FDTable) Fork(ctx context.Context) *FDTable {
 // Remove removes an FD from and returns a non-file iff successful.
 //
 // N.B. Callers are required to use DecRef when they are done.
-func (f *FDTable) Remove(fd int32) (*fs.File, *vfs.FileDescription) {
+func (f *FDTable) Remove(ctx context.Context, fd int32) (*fs.File, *vfs.FileDescription) {
 	if fd < 0 {
 		return nil, nil
 	}
@@ -618,7 +617,7 @@ func (f *FDTable) Remove(fd int32) (*fs.File, *vfs.FileDescription) {
 		orig2.IncRef()
 	}
 	if orig != nil || orig2 != nil {
-		f.setAll(fd, nil, nil, FDFlags{}) // Zap entry.
+		f.setAll(ctx, fd, nil, nil, FDFlags{}) // Zap entry.
 	}
 	return orig, orig2
 }
@@ -630,7 +629,7 @@ func (f *FDTable) RemoveIf(ctx context.Context, cond func(*fs.File, *vfs.FileDes
 
 	f.forEach(ctx, func(fd int32, file *fs.File, fileVFS2 *vfs.FileDescription, flags FDFlags) {
 		if cond(file, fileVFS2, flags) {
-			f.set(fd, nil, FDFlags{}) // Clear from table.
+			f.set(ctx, fd, nil, FDFlags{}) // Clear from table.
 			// Update current available position.
 			if fd < f.next {
 				f.next = fd
diff --git a/pkg/sentry/kernel/fd_table_test.go b/pkg/sentry/kernel/fd_table_test.go
index e3f30ba2a..bf5460083 100644
--- a/pkg/sentry/kernel/fd_table_test.go
+++ b/pkg/sentry/kernel/fd_table_test.go
@@ -72,7 +72,7 @@ func TestFDTableMany(t *testing.T) {
 		}
 
 		i := int32(2)
-		fdTable.Remove(i)
+		fdTable.Remove(ctx, i)
 		if fds, err := fdTable.NewFDs(ctx, 0, []*fs.File{file}, FDFlags{}); err != nil || fds[0] != i {
 			t.Fatalf("Allocated %v FDs but wanted to allocate %v: %v", i, maxFD, err)
 		}
@@ -93,7 +93,7 @@ func TestFDTableOverLimit(t *testing.T) {
 			t.Fatalf("fdTable.NewFDs(maxFD-3, {f,f,f}): got %v, wanted nil", err)
 		} else {
 			for _, fd := range fds {
-				fdTable.Remove(fd)
+				fdTable.Remove(ctx, fd)
 			}
 		}
 
@@ -150,13 +150,13 @@ func TestFDTable(t *testing.T) {
 			t.Fatalf("fdTable.Get(2): got a %v, wanted nil", ref)
 		}
 
-		ref, _ := fdTable.Remove(1)
+		ref, _ := fdTable.Remove(ctx, 1)
 		if ref == nil {
 			t.Fatalf("fdTable.Remove(1) for an existing FD: failed, want success")
 		}
 		ref.DecRef(ctx)
 
-		if ref, _ := fdTable.Remove(1); ref != nil {
+		if ref, _ := fdTable.Remove(ctx, 1); ref != nil {
 			t.Fatalf("r.Remove(1) for a removed FD: got success, want failure")
 		}
 	})
diff --git a/pkg/sentry/kernel/fd_table_unsafe.go b/pkg/sentry/kernel/fd_table_unsafe.go
index 6b8feb107..555b14f8e 100644
--- a/pkg/sentry/kernel/fd_table_unsafe.go
+++ b/pkg/sentry/kernel/fd_table_unsafe.go
@@ -18,6 +18,7 @@ import (
 	"sync/atomic"
 	"unsafe"
 
+	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 )
@@ -84,8 +85,8 @@ func (f *FDTable) getAll(fd int32) (*fs.File, *vfs.FileDescription, FDFlags, boo
 // reference needed by the table iff the file is different.
 //
 // Precondition: mu must be held.
-func (f *FDTable) set(fd int32, file *fs.File, flags FDFlags) {
-	f.setAll(fd, file, nil, flags)
+func (f *FDTable) set(ctx context.Context, fd int32, file *fs.File, flags FDFlags) {
+	f.setAll(ctx, fd, file, nil, flags)
 }
 
 // setVFS2 sets an entry.
@@ -94,8 +95,8 @@ func (f *FDTable) set(fd int32, file *fs.File, flags FDFlags) {
 // reference needed by the table iff the file is different.
 //
 // Precondition: mu must be held.
-func (f *FDTable) setVFS2(fd int32, file *vfs.FileDescription, flags FDFlags) {
-	f.setAll(fd, nil, file, flags)
+func (f *FDTable) setVFS2(ctx context.Context, fd int32, file *vfs.FileDescription, flags FDFlags) {
+	f.setAll(ctx, fd, nil, file, flags)
 }
 
 // setAll sets an entry.
@@ -104,7 +105,7 @@ func (f *FDTable) setVFS2(fd int32, file *vfs.FileDescription, flags FDFlags) {
 // reference needed by the table iff the file is different.
 //
 // Precondition: mu must be held.
-func (f *FDTable) setAll(fd int32, file *fs.File, fileVFS2 *vfs.FileDescription, flags FDFlags) {
+func (f *FDTable) setAll(ctx context.Context, fd int32, file *fs.File, fileVFS2 *vfs.FileDescription, flags FDFlags) {
 	if file != nil && fileVFS2 != nil {
 		panic("VFS1 and VFS2 files set")
 	}
@@ -152,11 +153,11 @@ func (f *FDTable) setAll(fd int32, file *fs.File, fileVFS2 *vfs.FileDescription,
 		switch {
 		case orig.file != nil:
 			if desc == nil || desc.file != orig.file {
-				f.drop(orig.file)
+				f.drop(ctx, orig.file)
 			}
 		case orig.fileVFS2 != nil:
 			if desc == nil || desc.fileVFS2 != orig.fileVFS2 {
-				f.dropVFS2(orig.fileVFS2)
+				f.dropVFS2(ctx, orig.fileVFS2)
 			}
 		}
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_file.go b/pkg/sentry/syscalls/linux/sys_file.go
index 256422689..07c77e442 100644
--- a/pkg/sentry/syscalls/linux/sys_file.go
+++ b/pkg/sentry/syscalls/linux/sys_file.go
@@ -601,12 +601,12 @@ func Ioctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	// Shared flags between file and socket.
 	switch request {
 	case linux.FIONCLEX:
-		t.FDTable().SetFlags(fd, kernel.FDFlags{
+		t.FDTable().SetFlags(t, fd, kernel.FDFlags{
 			CloseOnExec: false,
 		})
 		return 0, nil, nil
 	case linux.FIOCLEX:
-		t.FDTable().SetFlags(fd, kernel.FDFlags{
+		t.FDTable().SetFlags(t, fd, kernel.FDFlags{
 			CloseOnExec: true,
 		})
 		return 0, nil, nil
@@ -787,7 +787,7 @@ func Close(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	// Note that Remove provides a reference on the file that we may use to
 	// flush. It is still active until we drop the final reference below
 	// (and other reference-holding operations complete).
-	file, _ := t.FDTable().Remove(fd)
+	file, _ := t.FDTable().Remove(t, fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -941,7 +941,7 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		return uintptr(flags.ToLinuxFDFlags()), nil, nil
 	case linux.F_SETFD:
 		flags := args[2].Uint()
-		err := t.FDTable().SetFlags(fd, kernel.FDFlags{
+		err := t.FDTable().SetFlags(t, fd, kernel.FDFlags{
 			CloseOnExec: flags&linux.FD_CLOEXEC != 0,
 		})
 		return 0, nil, err
@@ -1154,6 +1154,10 @@ func Fadvise64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 	return 0, nil, nil
 }
 
+// LINT.ThenChange(vfs2/fd.go)
+
+// LINT.IfChange
+
 func mkdirAt(t *kernel.Task, dirFD int32, addr usermem.Addr, mode linux.FileMode) error {
 	path, _, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
diff --git a/pkg/sentry/syscalls/linux/sys_pipe.go b/pkg/sentry/syscalls/linux/sys_pipe.go
index 3149e4aad..c55beb39b 100644
--- a/pkg/sentry/syscalls/linux/sys_pipe.go
+++ b/pkg/sentry/syscalls/linux/sys_pipe.go
@@ -48,7 +48,7 @@ func pipe2(t *kernel.Task, addr usermem.Addr, flags uint) (uintptr, error) {
 
 	if _, err := t.CopyOut(addr, fds); err != nil {
 		for _, fd := range fds {
-			if file, _ := t.FDTable().Remove(fd); file != nil {
+			if file, _ := t.FDTable().Remove(t, fd); file != nil {
 				file.DecRef(t)
 			}
 		}
diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index 38f573c14..e4528d095 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -249,7 +249,7 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 	// Copy the file descriptors out.
 	if _, err := t.CopyOut(socks, fds); err != nil {
 		for _, fd := range fds {
-			if file, _ := t.FDTable().Remove(fd); file != nil {
+			if file, _ := t.FDTable().Remove(t, fd); file != nil {
 				file.DecRef(t)
 			}
 		}
diff --git a/pkg/sentry/syscalls/linux/vfs2/fd.go b/pkg/sentry/syscalls/linux/vfs2/fd.go
index 4856554fe..fdd8f88c5 100644
--- a/pkg/sentry/syscalls/linux/vfs2/fd.go
+++ b/pkg/sentry/syscalls/linux/vfs2/fd.go
@@ -34,7 +34,7 @@ func Close(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	// Note that Remove provides a reference on the file that we may use to
 	// flush. It is still active until we drop the final reference below
 	// (and other reference-holding operations complete).
-	_, file := t.FDTable().Remove(fd)
+	_, file := t.FDTable().Remove(t, fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -137,7 +137,7 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		return uintptr(flags.ToLinuxFDFlags()), nil, nil
 	case linux.F_SETFD:
 		flags := args[2].Uint()
-		err := t.FDTable().SetFlagsVFS2(fd, kernel.FDFlags{
+		err := t.FDTable().SetFlagsVFS2(t, fd, kernel.FDFlags{
 			CloseOnExec: flags&linux.FD_CLOEXEC != 0,
 		})
 		return 0, nil, err
diff --git a/pkg/sentry/syscalls/linux/vfs2/ioctl.go b/pkg/sentry/syscalls/linux/vfs2/ioctl.go
index 38778a388..baa8a49af 100644
--- a/pkg/sentry/syscalls/linux/vfs2/ioctl.go
+++ b/pkg/sentry/syscalls/linux/vfs2/ioctl.go
@@ -34,13 +34,13 @@ func Ioctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	// Handle ioctls that apply to all FDs.
 	switch args[1].Int() {
 	case linux.FIONCLEX:
-		t.FDTable().SetFlagsVFS2(fd, kernel.FDFlags{
+		t.FDTable().SetFlagsVFS2(t, fd, kernel.FDFlags{
 			CloseOnExec: false,
 		})
 		return 0, nil, nil
 
 	case linux.FIOCLEX:
-		t.FDTable().SetFlagsVFS2(fd, kernel.FDFlags{
+		t.FDTable().SetFlagsVFS2(t, fd, kernel.FDFlags{
 			CloseOnExec: true,
 		})
 		return 0, nil, nil
diff --git a/pkg/sentry/syscalls/linux/vfs2/pipe.go b/pkg/sentry/syscalls/linux/vfs2/pipe.go
index 9b4848d9e..3aa6d939d 100644
--- a/pkg/sentry/syscalls/linux/vfs2/pipe.go
+++ b/pkg/sentry/syscalls/linux/vfs2/pipe.go
@@ -53,7 +53,7 @@ func pipe2(t *kernel.Task, addr usermem.Addr, flags int32) error {
 	}
 	if _, err := t.CopyOut(addr, fds); err != nil {
 		for _, fd := range fds {
-			if _, file := t.FDTable().Remove(fd); file != nil {
+			if _, file := t.FDTable().Remove(t, fd); file != nil {
 				file.DecRef(t)
 			}
 		}
diff --git a/pkg/sentry/syscalls/linux/vfs2/socket.go b/pkg/sentry/syscalls/linux/vfs2/socket.go
index a5032657a..a15dad29f 100644
--- a/pkg/sentry/syscalls/linux/vfs2/socket.go
+++ b/pkg/sentry/syscalls/linux/vfs2/socket.go
@@ -252,7 +252,7 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 	if _, err := t.CopyOut(addr, fds); err != nil {
 		for _, fd := range fds {
-			if _, file := t.FDTable().Remove(fd); file != nil {
+			if _, file := t.FDTable().Remove(t, fd); file != nil {
 				file.DecRef(t)
 			}
 		}