linux-kernel - [PATCH] stacktrace: Use PF_KTHREAD to check for kernel threads

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Message-ID: <alpine.DEB.2.21.1907021750100.1802@nanos.tec.linutronix.de>
Date:   Tue, 2 Jul 2019 17:53:35 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH] stacktrace: Use PF_KTHREAD to check for kernel threads

!current->mm is not a reliable indicator for kernel threads as they might
temporarily use a user mm. Check for PF_KTHREAD instead.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -228,7 +228,7 @@ unsigned int stack_trace_save_user(unsig
 	};
 
 	/* Trace user stack if not a kernel thread */
-	if (!current->mm)
+	if (current->flags & PF_KTHREAD)
 		return 0;
 
 	arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));