[syserror] Add conversions to linuxerr with temporary Equals method.

Add Equals method to compare syserror and unix.Errno errors to linuxerr errors.
This will facilitate removal of syserror definitions in a followup, and
finding needed conversions from unix.Errno to linuxerr.

PiperOrigin-RevId: 380909667

3 files changed, 13 insertions, 7 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/BUILD b/pkg/sentry/fsimpl/kernfs/BUILD
index b7d13cced..d53937db6 100644
--- a/pkg/sentry/fsimpl/kernfs/BUILD
+++ b/pkg/sentry/fsimpl/kernfs/BUILD
@@ -104,6 +104,7 @@ go_library(
     deps = [
         "//pkg/abi/linux",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/fspath",
         "//pkg/hostarch",
         "//pkg/log",
@@ -135,6 +136,7 @@ go_test(
         ":kernfs",
         "//pkg/abi/linux",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/log",
         "//pkg/refs",
         "//pkg/refsvfs2",
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index 8fac53c60..20319ab76 100644
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -21,6 +21,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
@@ -411,7 +412,7 @@ func (fs *Filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
 	defer rp.Mount().EndWrite()
 	childI, err := parent.inode.NewDir(ctx, pc, opts)
 	if err != nil {
-		if !opts.ForSyntheticMountpoint || err == syserror.EEXIST {
+		if !opts.ForSyntheticMountpoint || linuxerr.Equals(linuxerr.EEXIST, err) {
 			return err
 		}
 		childI = newSyntheticDirectory(ctx, rp.Credentials(), opts.Mode)
@@ -546,7 +547,7 @@ afterTrailingSymlink:
 	}
 	// Determine whether or not we need to create a file.
 	child, err := fs.stepExistingLocked(ctx, rp, parent, false /* mayFollowSymlinks */)
-	if err == syserror.ENOENT {
+	if linuxerr.Equals(linuxerr.ENOENT, err) {
 		// Already checked for searchability above; now check for writability.
 		if err := parent.inode.CheckPermissions(ctx, rp.Credentials(), vfs.MayWrite); err != nil {
 			return nil, err
@@ -684,10 +685,12 @@ func (fs *Filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 		}
 		return syserror.EBUSY
 	}
-	switch err := checkCreateLocked(ctx, rp.Credentials(), newName, dstDir); err {
-	case nil:
+
+	err = checkCreateLocked(ctx, rp.Credentials(), newName, dstDir)
+	switch {
+	case err == nil:
 		// Ok, continue with rename as replacement.
-	case syserror.EEXIST:
+	case linuxerr.Equals(linuxerr.EEXIST, err):
 		if noReplace {
 			// Won't overwrite existing node since RENAME_NOREPLACE was requested.
 			return syserror.EEXIST
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs_test.go b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
index 1cd3137e6..de046ce1f 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs_test.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
@@ -22,6 +22,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/sentry/contexttest"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/testutil"
@@ -318,10 +319,10 @@ func TestDirFDReadWrite(t *testing.T) {
 	defer fd.DecRef(sys.Ctx)
 
 	// Read/Write should fail for directory FDs.
-	if _, err := fd.Read(sys.Ctx, usermem.BytesIOSequence([]byte{}), vfs.ReadOptions{}); err != syserror.EISDIR {
+	if _, err := fd.Read(sys.Ctx, usermem.BytesIOSequence([]byte{}), vfs.ReadOptions{}); !linuxerr.Equals(linuxerr.EISDIR, err) {
 		t.Fatalf("Read for directory FD failed with unexpected error: %v", err)
 	}
-	if _, err := fd.Write(sys.Ctx, usermem.BytesIOSequence([]byte{}), vfs.WriteOptions{}); err != syserror.EBADF {
+	if _, err := fd.Write(sys.Ctx, usermem.BytesIOSequence([]byte{}), vfs.WriteOptions{}); !linuxerr.Equals(linuxerr.EBADF, err) {
 		t.Fatalf("Write for directory FD failed with unexpected error: %v", err)
 	}
 }