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@linutronix.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1907021750100.1802@nanos.tec.linutronix.de

diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 36139de0a3c4bcb7ba7da936a8d43fba08aa5929..c8d0f05721a1100cd2e77020ae07f6d553c95501 100644 (file)
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -228,7 +228,7 @@ unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
        };
 
        /* 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));