linux-kernel - [PATCH 5.4 196/222] um: Dont trace irqflags during shutdown

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Date:   Wed, 22 Jan 2020 10:29:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johannes Berg <johannes.berg@...el.com>,
        Richard Weinberger <richard@....at>
Subject: [PATCH 5.4 196/222] um: Dont trace irqflags during shutdown

From: Johannes Berg <johannes.berg@...el.com>

commit 5c1f33e2a03c0b8710b5d910a46f1e1fb0607679 upstream.

In the main() code, we eventually enable signals just before
exec() or exit(), in order to to not have signals pending and
delivered *after* the exec().

I've observed SIGSEGV loops at this point, and the reason seems
to be the irqflags tracing; this makes sense as the kernel is
no longer really functional at this point. Since there's really
no reason to use unblock_signals_trace() here (I had just done
a global search & replace), use the plain unblock_signals() in
this case to avoid going into the no longer functional kernel.

Fixes: 0dafcbe128d2 ("um: Implement TRACE_IRQFLAGS_SUPPORT")
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Richard Weinberger <richard@....at>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/um/os-Linux/main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -170,7 +170,7 @@ int __init main(int argc, char **argv, c
 	 * that they won't be delivered after the exec, when
 	 * they are definitely not expected.
 	 */
-	unblock_signals_trace();
+	unblock_signals();

 	os_info("\n");
 	/* Reboot */