Index: src/sys/kern/vfs_syscalls.c
@@ -69,6 +69,7 @@ __FBSDID("$FreeBSD: src/sys/kern/vfs_sys
 #include <sys/jail.h>
 #include <sys/syscallsubr.h>
 #include <sys/sysctl.h>
+#include <sys/disk.h>
 #ifdef KTRACE
 #include <sys/ktrace.h>
 #endif
@@ -1940,19 +1941,26 @@ lseek(td, uap)
 		offset += fp->f_offset;
 		break;
 	case L_XTND:
+	{
+		off_t size;
+
 		vn_lock(vp, LK_SHARED | LK_RETRY);
 		error = VOP_GETATTR(vp, &vattr, cred);
 		VOP_UNLOCK(vp, 0);
 		if (error)
 			break;
+		size = vattr.va_size;
+		if (!size && vp->v_type == VCHR && vn_isdisk(vp, NULL))
+		    fo_ioctl(fp, DIOCGMEDIASIZE, &size, cred, td);
 		if (noneg &&
-		    (vattr.va_size > OFF_MAX ||
-		    (offset > 0 && vattr.va_size > OFF_MAX - offset))) {
+		    (size > OFF_MAX ||
+		    (offset > 0 && size > OFF_MAX - offset))) {
 			error = EOVERFLOW;
 			break;
 		}
-		offset += vattr.va_size;
+		offset += size;
 		break;
+	}
 	case L_SET:
 		break;
 	case SEEK_DATA: