1 files changed, 25 insertions, 12 deletions

diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c
index 57fd4e902f1f..f515aa7cc9e5 100644
--- a/arch/s390/kernel/unwind_bc.c
+++ b/arch/s390/kernel/unwind_bc.c
@@ -46,18 +46,28 @@ bool unwind_next_frame(struct unwind_state *state)
 
 	regs = state->regs;
 	if (unlikely(regs)) {
-		sp = READ_ONCE_TASK_STACK(state->task, regs->gprs[15]);
-		if (unlikely(outside_of_stack(state, sp))) {
-			if (!update_stack_info(state, sp))
-				goto out_err;
+		if (state->reuse_sp) {
+			sp = state->sp;
+			state->reuse_sp = false;
+		} else {
+			sp = READ_ONCE_NOCHECK(regs->gprs[15]);
+			if (unlikely(outside_of_stack(state, sp))) {
+				if (!update_stack_info(state, sp))
+					goto out_err;
+			}
 		}
 		sf = (struct stack_frame *) sp;
-		ip = READ_ONCE_TASK_STACK(state->task, sf->gprs[8]);
+		ip = READ_ONCE_NOCHECK(sf->gprs[8]);
 		reliable = false;
 		regs = NULL;
+		if (!__kernel_text_address(ip)) {
+			/* skip bogus %r14 */
+			state->regs = NULL;
+			return unwind_next_frame(state);
+		}
 	} else {
 		sf = (struct stack_frame *) state->sp;
-		sp = READ_ONCE_TASK_STACK(state->task, sf->back_chain);
+		sp = READ_ONCE_NOCHECK(sf->back_chain);
 		if (likely(sp)) {
 			/* Non-zero back-chain points to the previous frame */
 			if (unlikely(outside_of_stack(state, sp))) {
@@ -65,7 +75,7 @@ bool unwind_next_frame(struct unwind_state *state)
 					goto out_err;
 			}
 			sf = (struct stack_frame *) sp;
-			ip = READ_ONCE_TASK_STACK(state->task, sf->gprs[8]);
+			ip = READ_ONCE_NOCHECK(sf->gprs[8]);
 			reliable = true;
 		} else {
 			/* No back-chain, look for a pt_regs structure */
@@ -73,9 +83,9 @@ bool unwind_next_frame(struct unwind_state *state)
 			if (!on_stack(info, sp, sizeof(struct pt_regs)))
 				goto out_stop;
 			regs = (struct pt_regs *) sp;
-			if (user_mode(regs))
+			if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE)
 				goto out_stop;
-			ip = READ_ONCE_TASK_STACK(state->task, regs->psw.addr);
+			ip = READ_ONCE_NOCHECK(regs->psw.addr);
 			reliable = true;
 		}
 	}
@@ -107,9 +117,9 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
 {
 	struct stack_info *info = &state->stack_info;
 	unsigned long *mask = &state->stack_mask;
+	bool reliable, reuse_sp;
 	struct stack_frame *sf;
 	unsigned long ip;
-	bool reliable;
 
 	memset(state, 0, sizeof(*state));
 	state->task = task;
@@ -132,12 +142,14 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
 
 	/* Get the instruction pointer from pt_regs or the stack frame */
 	if (regs) {
-		ip = READ_ONCE_TASK_STACK(state->task, regs->psw.addr);
+		ip = READ_ONCE_NOCHECK(regs->psw.addr);
 		reliable = true;
+		reuse_sp = true;
 	} else {
 		sf = (struct stack_frame *) sp;
-		ip = READ_ONCE_TASK_STACK(state->task, sf->gprs[8]);
+		ip = READ_ONCE_NOCHECK(sf->gprs[8]);
 		reliable = false;
+		reuse_sp = false;
 	}
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -151,5 +163,6 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
 	state->sp = sp;
 	state->ip = ip;
 	state->reliable = reliable;
+	state->reuse_sp = reuse_sp;
 }
 EXPORT_SYMBOL_GPL(__unwind_start);