Change sizeofInt32 to string size

This constant is used to represent int32 stored in file xattrs. The
integers are stored as strings there, so the real size should be the
string size (number of digits) instead of an int size (4 bytes).

PiperOrigin-RevId: 332353217

pkg/sentry/fsimpl/verity/filesystem.go

@@ -185,8 +185,7 @@ func (fs *filesystem) verifyChild(ctx context.Context, parent *dentry, child *de
 		Start: child.lowerMerkleVD,
 	}, &vfs.GetXattrOptions{
 		Name: merkleOffsetInParentXattr,
-		// Offset is a 32 bit integer.
-		Size: sizeOfInt32,
+		Size: sizeOfStringInt32,
 	})
 
 	// The Merkle tree file for the child should have been created and
@@ -227,7 +226,7 @@ func (fs *filesystem) verifyChild(ctx context.Context, parent *dentry, child *de
 	// the size of all its children's root hashes.
 	dataSize, err := parentMerkleFD.GetXattr(ctx, &vfs.GetXattrOptions{
 		Name: merkleSizeXattr,
-		Size: sizeOfInt32,
+		Size: sizeOfStringInt32,
 	})
 
 	// The Merkle tree file for the child should have been created and

pkg/sentry/fsimpl/verity/verity.go

@@ -57,8 +57,9 @@ const merkleOffsetInParentXattr = "user.merkle.offset"
 // whole file. For a directory, it's the size of all its children's root hashes.
 const merkleSizeXattr = "user.merkle.size"
 
-// sizeOfInt32 is the size in bytes for a 32 bit integer in extended attributes.
-const sizeOfInt32 = 4
+// sizeOfStringInt32 is the size for a 32 bit integer stored as string in
+// extended attributes. The maximum value of a 32 bit integer is 10 digits.
+const sizeOfStringInt32 = 10
 
 // noCrashOnVerificationFailure indicates whether the sandbox should panic
 // whenever verification fails. If true, an error is returned instead of
@@ -636,7 +637,7 @@ func (fd *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, of
 	// dataSize is the size of the whole file.
 	dataSize, err := fd.merkleReader.GetXattr(ctx, &vfs.GetXattrOptions{
 		Name: merkleSizeXattr,
-		Size: sizeOfInt32,
+		Size: sizeOfStringInt32,
 	})
 
 	// The Merkle tree file for the child should have been created and