diff --git a/sys/fs/smbfs/smbfs_io.c b/sys/fs/smbfs/smbfs_io.c
index 505c90643d2..0f3f20e2614 100644
--- a/sys/fs/smbfs/smbfs_io.c
+++ b/sys/fs/smbfs/smbfs_io.c
@@ -273,7 +273,9 @@ smbfs_writevnode(struct vnode *vp, struct uio *uiop,
 	if (uiop->uio_resid == 0)
 		return 0;
 	if (p && uiop->uio_offset + uiop->uio_resid > p->p_rlimit[RLIMIT_FSIZE].rlim_cur) {
+		PROC_LOCK(p);
 		psignal(p, SIGXFSZ);
+		PROC_UNLOCK(p);
 		return EFBIG;
 	}
 	smb_makescred(&scred, p, cred);