rseq: Set rseq::cpu_id_start to 0 on unregistration

The RSEQ rework changed that to RSEQ_CPU_UNINITILIZED, which is obviously incompatible. Revert back to the original behavior.

Thomas Gleixner committed 6 months ago

Commit 2cb68e41 parent cb488281 file · +9 −11Browse files

Showing the changes to kernel (1 of 1 file). Show all

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 }
 __initcall(rseq_debugfs_init);
-static bool rseq_set_ids(struct task_struct *t, struct rseq_ids *ids, u32 node_id)
-{
-	return rseq_set_ids_get_csaddr(t, ids, node_id, NULL);
-}
 static bool rseq_handle_cs(struct task_struct *t, struct pt_regs *regs)
 {
 	struct rseq __user *urseq = t->rseq.usrptr;
 static bool rseq_reset_ids(void)
 {
-	struct rseq_ids ids = {
+	struct rseq __user *rseq = current->rseq.usrptr;
-		.cpu_id		= RSEQ_CPU_ID_UNINITIALIZED,
-		.mm_cid		= 0,
-	};
 	/*
 	 * If this fails, terminate it because this leaves the kernel in
 	 * stupid state as exit to user space will try to fixup the ids
 	 * again.
 	 */
-	if (rseq_set_ids(current, &ids, 0))
+	scoped_user_rw_access(rseq, efault) {
-		return true;
+		unsafe_put_user(0, &rseq->cpu_id_start, efault);
+		unsafe_put_user(RSEQ_CPU_ID_UNINITIALIZED, &rseq->cpu_id, efault);
+		unsafe_put_user(0, &rseq->node_id, efault);
+		unsafe_put_user(0, &rseq->mm_cid, efault);
+	}
+	return true;
+efault:
 	force_sig(SIGSEGV);
 	return false;
 }