Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Catalin Marinas:

 - arm64 stacktrace: address some fallout from the recent changes to
   unwinding across exception boundaries

 - Ensure the arm64 signal delivery failure is recoverable - only
   override the return registers after all the user accesses took place

 - Fix the arm64 kselftest access to SVCR - only when SME is detected

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  kselftest/arm64: abi: fix SVCR detection
  arm64: signal: Ensure signal delivery failure is recoverable
  arm64: stacktrace: Don't WARN when unwinding other tasks
  arm64: stacktrace: Skip reporting LR at exception boundaries

2 files changed, 40 insertions, 40 deletions

diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 14ac6fdb872b..37e24f1bd227 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -1462,10 +1462,33 @@ static int setup_return(struct pt_regs *regs, struct ksignal *ksig,
 			 struct rt_sigframe_user_layout *user, int usig)
 {
 	__sigrestore_t sigtramp;
+	int err;
+
+	if (ksig->ka.sa.sa_flags & SA_RESTORER)
+		sigtramp = ksig->ka.sa.sa_restorer;
+	else
+		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
+
+	err = gcs_signal_entry(sigtramp, ksig);
+	if (err)
+		return err;
+
+	/*
+	 * We must not fail from this point onwards. We are going to update
+	 * registers, including SP, in order to invoke the signal handler. If
+	 * we failed and attempted to deliver a nested SIGSEGV to a handler
+	 * after that point, the subsequent sigreturn would end up restoring
+	 * the (partial) state for the original signal handler.
+	 */
 
 	regs->regs[0] = usig;
+	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
+		regs->regs[1] = (unsigned long)&user->sigframe->info;
+		regs->regs[2] = (unsigned long)&user->sigframe->uc;
+	}
 	regs->sp = (unsigned long)user->sigframe;
 	regs->regs[29] = (unsigned long)&user->next_frame->fp;
+	regs->regs[30] = (unsigned long)sigtramp;
 	regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
 
 	/*
@@ -1506,14 +1529,7 @@ static int setup_return(struct pt_regs *regs, struct ksignal *ksig,
 		sme_smstop();
 	}
 
-	if (ksig->ka.sa.sa_flags & SA_RESTORER)
-		sigtramp = ksig->ka.sa.sa_restorer;
-	else
-		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
-
-	regs->regs[30] = (unsigned long)sigtramp;
-
-	return gcs_signal_entry(sigtramp, ksig);
+	return 0;
 }
 
 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
@@ -1537,14 +1553,16 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 
 	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 	err |= setup_sigframe(&user, regs, set, &ua_state);
-	if (err == 0) {
+	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
+		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
+
+	if (err == 0)
 		err = setup_return(regs, ksig, &user, usig);
-		if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
-			err |= copy_siginfo_to_user(&frame->info, &ksig->info);
-			regs->regs[1] = (unsigned long)&frame->info;
-			regs->regs[2] = (unsigned long)&frame->uc;
-		}
-	}
+
+	/*
+	 * We must not fail if setup_return() succeeded - see comment at the
+	 * beginning of setup_return().
+	 */
 
 	if (err == 0)
 		set_handler_user_access_state();
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index caef85462acb..1d9d51d7627f 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -26,7 +26,6 @@ enum kunwind_source {
 	KUNWIND_SOURCE_CALLER,
 	KUNWIND_SOURCE_TASK,
 	KUNWIND_SOURCE_REGS_PC,
-	KUNWIND_SOURCE_REGS_LR,
 };
 
 union unwind_flags {
@@ -138,8 +137,10 @@ kunwind_recover_return_address(struct kunwind_state *state)
 		orig_pc = ftrace_graph_ret_addr(state->task, &state->graph_idx,
 						state->common.pc,
 						(void *)state->common.fp);
-		if (WARN_ON_ONCE(state->common.pc == orig_pc))
+		if (state->common.pc == orig_pc) {
+			WARN_ON_ONCE(state->task == current);
 			return -EINVAL;
+		}
 		state->common.pc = orig_pc;
 		state->flags.fgraph = 1;
 	}
@@ -178,23 +179,8 @@ int kunwind_next_regs_pc(struct kunwind_state *state)
 	state->regs = regs;
 	state->common.pc = regs->pc;
 	state->common.fp = regs->regs[29];
-	state->source = KUNWIND_SOURCE_REGS_PC;
-	return 0;
-}
-
-static __always_inline int
-kunwind_next_regs_lr(struct kunwind_state *state)
-{
-	/*
-	 * The stack for the regs was consumed by kunwind_next_regs_pc(), so we
-	 * cannot consume that again here, but we know the regs are safe to
-	 * access.
-	 */
-	state->common.pc = state->regs->regs[30];
-	state->common.fp = state->regs->regs[29];
 	state->regs = NULL;
-	state->source = KUNWIND_SOURCE_REGS_LR;
-
+	state->source = KUNWIND_SOURCE_REGS_PC;
 	return 0;
 }
 
@@ -215,12 +201,12 @@ kunwind_next_frame_record_meta(struct kunwind_state *state)
 	case FRAME_META_TYPE_FINAL:
 		if (meta == &task_pt_regs(tsk)->stackframe)
 			return -ENOENT;
-		WARN_ON_ONCE(1);
+		WARN_ON_ONCE(tsk == current);
 		return -EINVAL;
 	case FRAME_META_TYPE_PT_REGS:
 		return kunwind_next_regs_pc(state);
 	default:
-		WARN_ON_ONCE(1);
+		WARN_ON_ONCE(tsk == current);
 		return -EINVAL;
 	}
 }
@@ -274,11 +260,8 @@ kunwind_next(struct kunwind_state *state)
 	case KUNWIND_SOURCE_FRAME:
 	case KUNWIND_SOURCE_CALLER:
 	case KUNWIND_SOURCE_TASK:
-	case KUNWIND_SOURCE_REGS_LR:
-		err = kunwind_next_frame_record(state);
-		break;
 	case KUNWIND_SOURCE_REGS_PC:
-		err = kunwind_next_regs_lr(state);
+		err = kunwind_next_frame_record(state);
 		break;
 	default:
 		err = -EINVAL;
@@ -436,7 +419,6 @@ static const char *state_source_string(const struct kunwind_state *state)
 	case KUNWIND_SOURCE_CALLER:	return "C";
 	case KUNWIND_SOURCE_TASK:	return "T";
 	case KUNWIND_SOURCE_REGS_PC:	return "P";
-	case KUNWIND_SOURCE_REGS_LR:	return "L";
 	default:			return "U";
 	}
 }