Add syscalls for lgetxattr, fgetxattr, lsetxattr, and fsetxattr.

Note that these simply will use the same logic as getxattr and setxattr, which
is not yet implemented for most filesystems.

PiperOrigin-RevId: 290800960

pkg/sentry/syscalls/linux/linux64_amd64.go

@@ -229,11 +229,11 @@ var AMD64 = &kernel.SyscallTable{
 		186: syscalls.Supported("gettid", Gettid),
 		187: syscalls.Supported("readahead", Readahead),
 		188: syscalls.PartiallySupported("setxattr", SetXattr, "Only supported for tmpfs.", nil),
-		189: syscalls.Error("lsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
-		190: syscalls.Error("fsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		189: syscalls.PartiallySupported("lsetxattr", LSetXattr, "Only supported for tmpfs.", nil),
+		190: syscalls.PartiallySupported("fsetxattr", FSetXattr, "Only supported for tmpfs.", nil),
 		191: syscalls.PartiallySupported("getxattr", GetXattr, "Only supported for tmpfs.", nil),
-		192: syscalls.ErrorWithEvent("lgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
-		193: syscalls.ErrorWithEvent("fgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		192: syscalls.PartiallySupported("lgetxattr", LGetXattr, "Only supported for tmpfs.", nil),
+		193: syscalls.PartiallySupported("fgetxattr", FGetXattr, "Only supported for tmpfs.", nil),
 		194: syscalls.ErrorWithEvent("listxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
 		195: syscalls.ErrorWithEvent("llistxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
 		196: syscalls.ErrorWithEvent("flistxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),

pkg/sentry/syscalls/linux/linux64_arm64.go

@@ -42,11 +42,11 @@ var ARM64 = &kernel.SyscallTable{
 		3:   syscalls.PartiallySupported("io_cancel", IoCancel, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}),
 		4:   syscalls.PartiallySupported("io_getevents", IoGetevents, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}),
 		5:   syscalls.PartiallySupported("setxattr", SetXattr, "Only supported for tmpfs.", nil),
-		6:   syscalls.Error("lsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
-		7:   syscalls.Error("fsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		6:   syscalls.PartiallySupported("lsetxattr", LSetXattr, "Only supported for tmpfs.", nil),
+		7:   syscalls.PartiallySupported("fsetxattr", FSetXattr, "Only supported for tmpfs.", nil),
 		8:   syscalls.PartiallySupported("getxattr", GetXattr, "Only supported for tmpfs.", nil),
-		9:   syscalls.ErrorWithEvent("lgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
-		10:  syscalls.ErrorWithEvent("fgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		9:   syscalls.PartiallySupported("lgetxattr", LGetXattr, "Only supported for tmpfs.", nil),
+		10:  syscalls.PartiallySupported("fgetxattr", FGetXattr, "Only supported for tmpfs.", nil),
 		11:  syscalls.ErrorWithEvent("listxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
 		12:  syscalls.ErrorWithEvent("llistxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
 		13:  syscalls.ErrorWithEvent("flistxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),

pkg/sentry/syscalls/linux/sys_xattr.go

@@ -27,6 +27,40 @@ import (
 
 // GetXattr implements linux syscall getxattr(2).
 func GetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return getXattrFromPath(t, args, true)
+}
+
+// LGetXattr implements linux syscall lgetxattr(2).
+func LGetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return getXattrFromPath(t, args, false)
+}
+
+// FGetXattr implements linux syscall fgetxattr(2).
+func FGetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := uint64(args[3].SizeT())
+
+	// TODO(b/113957122): Return EBADF if the fd was opened with O_PATH.
+	f := t.GetFile(fd)
+	if f == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer f.DecRef()
+
+	n, value, err := getXattr(t, f.Dirent, nameAddr, size)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	if _, err := t.CopyOutBytes(valueAddr, []byte(value)); err != nil {
+		return 0, nil, err
+	}
+	return uintptr(n), nil, nil
+}
+
+func getXattrFromPath(t *kernel.Task, args arch.SyscallArguments, resolveSymlink bool) (uintptr, *kernel.SyscallControl, error) {
 	pathAddr := args[0].Pointer()
 	nameAddr := args[1].Pointer()
 	valueAddr := args[2].Pointer()
@@ -38,29 +72,17 @@ func GetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	}
 
 	valueLen := 0
-	err = fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
-		// If getxattr(2) is called with size 0, the size of the value will be
-		// returned successfully even if it is nonzero. In that case, we need to
-		// retrieve the entire attribute value so we can return the correct size.
-		requestedSize := size
-		if size == 0 || size > linux.XATTR_SIZE_MAX {
-			requestedSize = linux.XATTR_SIZE_MAX
+	err = fileOpOn(t, linux.AT_FDCWD, path, resolveSymlink, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
+		if dirPath && !fs.IsDir(d.Inode.StableAttr) {
+			return syserror.ENOTDIR
 		}
 
-		value, err := getXattr(t, d, dirPath, nameAddr, uint64(requestedSize))
+		n, value, err := getXattr(t, d, nameAddr, size)
+		valueLen = n
 		if err != nil {
 			return err
 		}
 
-		valueLen = len(value)
-		if uint64(valueLen) > requestedSize {
-			return syserror.ERANGE
-		}
-
-		// Skip copying out the attribute value if size is 0.
-		if size == 0 {
-			return nil
-		}
 		_, err = t.CopyOutBytes(valueAddr, []byte(value))
 		return err
 	})
@@ -71,29 +93,73 @@ func GetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 }
 
 // getXattr implements getxattr(2) from the given *fs.Dirent.
-func getXattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr usermem.Addr, size uint64) (string, error) {
-	if dirPath && !fs.IsDir(d.Inode.StableAttr) {
-		return "", syserror.ENOTDIR
-	}
-
+func getXattr(t *kernel.Task, d *fs.Dirent, nameAddr usermem.Addr, size uint64) (int, string, error) {
 	if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Read: true}); err != nil {
-		return "", err
+		return 0, "", err
 	}
 
 	name, err := copyInXattrName(t, nameAddr)
 	if err != nil {
-		return "", err
+		return 0, "", err
 	}
 
 	if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
-		return "", syserror.EOPNOTSUPP
+		return 0, "", syserror.EOPNOTSUPP
 	}
 
-	return d.Inode.GetXattr(t, name, size)
+	// If getxattr(2) is called with size 0, the size of the value will be
+	// returned successfully even if it is nonzero. In that case, we need to
+	// retrieve the entire attribute value so we can return the correct size.
+	requestedSize := size
+	if size == 0 || size > linux.XATTR_SIZE_MAX {
+		requestedSize = linux.XATTR_SIZE_MAX
+	}
+
+	value, err := d.Inode.GetXattr(t, name, requestedSize)
+	if err != nil {
+		return 0, "", err
+	}
+	n := len(value)
+	if uint64(n) > requestedSize {
+		return 0, "", syserror.ERANGE
+	}
+
+	// Don't copy out the attribute value if size is 0.
+	if size == 0 {
+		return n, "", nil
+	}
+	return n, value, nil
 }
 
 // SetXattr implements linux syscall setxattr(2).
 func SetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return setXattrFromPath(t, args, true)
+}
+
+// LSetXattr implements linux syscall lsetxattr(2).
+func LSetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return setXattrFromPath(t, args, false)
+}
+
+// FSetXattr implements linux syscall fsetxattr(2).
+func FSetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := uint64(args[3].SizeT())
+	flags := args[4].Uint()
+
+	// TODO(b/113957122): Return EBADF if the fd was opened with O_PATH.
+	f := t.GetFile(fd)
+	if f == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer f.DecRef()
+
+	return 0, nil, setXattr(t, f.Dirent, nameAddr, valueAddr, uint64(size), flags)
+}
+
+func setXattrFromPath(t *kernel.Task, args arch.SyscallArguments, resolveSymlink bool) (uintptr, *kernel.SyscallControl, error) {
 	pathAddr := args[0].Pointer()
 	nameAddr := args[1].Pointer()
 	valueAddr := args[2].Pointer()
@@ -105,19 +171,19 @@ func SetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 		return 0, nil, err
 	}
 
-	if flags&^(linux.XATTR_CREATE|linux.XATTR_REPLACE) != 0 {
-		return 0, nil, syserror.EINVAL
-	}
+	return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, resolveSymlink, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
+		if dirPath && !fs.IsDir(d.Inode.StableAttr) {
+			return syserror.ENOTDIR
+		}
 
-	return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
-		return setXattr(t, d, dirPath, nameAddr, valueAddr, uint64(size), flags)
+		return setXattr(t, d, nameAddr, valueAddr, uint64(size), flags)
 	})
 }
 
 // setXattr implements setxattr(2) from the given *fs.Dirent.
-func setXattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr usermem.Addr, size uint64, flags uint32) error {
-	if dirPath && !fs.IsDir(d.Inode.StableAttr) {
-		return syserror.ENOTDIR
+func setXattr(t *kernel.Task, d *fs.Dirent, nameAddr, valueAddr usermem.Addr, size uint64, flags uint32) error {
+	if flags&^(linux.XATTR_CREATE|linux.XATTR_REPLACE) != 0 {
+		return syserror.EINVAL
 	}
 
 	if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Write: true}); err != nil {
@@ -133,7 +199,7 @@ func setXattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr us
 		return syserror.E2BIG
 	}
 	buf := make([]byte, size)
-	if _, err = t.CopyInBytes(valueAddr, buf); err != nil {
+	if _, err := t.CopyInBytes(valueAddr, buf); err != nil {
 		return err
 	}
 	value := string(buf)

test/syscalls/linux/xattr.cc

@@ -26,6 +26,7 @@
 #include "gtest/gtest.h"
 #include "test/syscalls/linux/file_base.h"
 #include "test/util/capability_util.h"
+#include "test/util/file_descriptor.h"
 #include "test/util/posix_error.h"
 #include "test/util/temp_path.h"
 #include "test/util/test_util.h"
@@ -414,6 +415,46 @@ TEST_F(XattrTest, GetxattrNonexistentName) {
   EXPECT_THAT(getxattr(path, name, nullptr, 0), SyscallFailsWithErrno(ENODATA));
 }
 
+TEST_F(XattrTest, LGetSetxattrOnSymlink) {
+  TempPath dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  TempPath link = ASSERT_NO_ERRNO_AND_VALUE(
+      TempPath::CreateSymlinkTo(dir.path(), test_file_name_));
+
+  EXPECT_THAT(lsetxattr(link.path().c_str(), nullptr, nullptr, 0, 0),
+              SyscallFailsWithErrno(EPERM));
+  EXPECT_THAT(lgetxattr(link.path().c_str(), nullptr, nullptr, 0),
+              SyscallFailsWithErrno(ENODATA));
+}
+
+TEST_F(XattrTest, LGetSetxattrOnNonsymlink) {
+  const char* path = test_file_name_.c_str();
+  const char name[] = "user.test";
+  int val = 1234;
+  size_t size = sizeof(val);
+  EXPECT_THAT(lsetxattr(path, name, &val, size, /*flags=*/0),
+              SyscallSucceeds());
+
+  int buf = 0;
+  EXPECT_THAT(lgetxattr(path, name, &buf, size),
+              SyscallSucceedsWithValue(size));
+  EXPECT_EQ(buf, val);
+}
+
+TEST_F(XattrTest, FGetSetxattr) {
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(test_file_name_.c_str(), 0));
+  const char name[] = "user.test";
+  int val = 1234;
+  size_t size = sizeof(val);
+  EXPECT_THAT(fsetxattr(fd.get(), name, &val, size, /*flags=*/0),
+              SyscallSucceeds());
+
+  int buf = 0;
+  EXPECT_THAT(fgetxattr(fd.get(), name, &buf, size),
+              SyscallSucceedsWithValue(size));
+  EXPECT_EQ(buf, val);
+}
+
 }  // namespace
 
 }  // namespace testing