Patch "s390/ftrace: fix potential crashes when switching tracers" has been added to the 4.14-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    s390/ftrace: fix potential crashes when switching tracers

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-ftrace-fix-potential-crashes-when-switching-tra.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d96539f36aed3633a8629e99c73f13e1871759e3
Author: Philipp Rudo <prudo@xxxxxxxxxxxxx>
Date:   Mon Apr 6 14:47:48 2020 +0200

    s390/ftrace: fix potential crashes when switching tracers
    
    [ Upstream commit 8ebf6da9db1b2a20bb86cc1bee2552e894d03308 ]
    
    Switching tracers include instruction patching. To prevent that a
    instruction is patched while it's read the instruction patching is done
    in stop_machine 'context'. This also means that any function called
    during stop_machine must not be traced. Thus add 'notrace' to all
    functions called within stop_machine.
    
    Fixes: 1ec2772e0c3c ("s390/diag: add a statistic for diagnose calls")
    Fixes: 38f2c691a4b3 ("s390: improve wait logic of stop_machine")
    Fixes: 4ecf0a43e729 ("processor: get rid of cpu_relax_yield")
    Signed-off-by: Philipp Rudo <prudo@xxxxxxxxxxxxx>
    Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/s390/kernel/diag.c b/arch/s390/kernel/diag.c
index 35c842aa87058..4c7cf8787a848 100644
--- a/arch/s390/kernel/diag.c
+++ b/arch/s390/kernel/diag.c
@@ -128,7 +128,7 @@ void diag_stat_inc(enum diag_stat_enum nr)
 }
 EXPORT_SYMBOL(diag_stat_inc);
 
-void diag_stat_inc_norecursion(enum diag_stat_enum nr)
+void notrace diag_stat_inc_norecursion(enum diag_stat_enum nr)
 {
 	this_cpu_inc(diag_stat.counter[nr]);
 	trace_s390_diagnose_norecursion(diag_map[nr].code);
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index b649a6538350d..808f4fbe869e7 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -406,7 +406,7 @@ int smp_find_processor_id(u16 address)
 	return -1;
 }
 
-bool arch_vcpu_is_preempted(int cpu)
+bool notrace arch_vcpu_is_preempted(int cpu)
 {
 	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
 		return false;
@@ -416,7 +416,7 @@ bool arch_vcpu_is_preempted(int cpu)
 }
 EXPORT_SYMBOL(arch_vcpu_is_preempted);
 
-void smp_yield_cpu(int cpu)
+void notrace smp_yield_cpu(int cpu)
 {
 	if (MACHINE_HAS_DIAG9C) {
 		diag_stat_inc_norecursion(DIAG_STAT_X09C);
diff --git a/arch/s390/kernel/trace.c b/arch/s390/kernel/trace.c
index 490b52e850145..11a669f3cc93c 100644
--- a/arch/s390/kernel/trace.c
+++ b/arch/s390/kernel/trace.c
@@ -14,7 +14,7 @@ EXPORT_TRACEPOINT_SYMBOL(s390_diagnose);
 
 static DEFINE_PER_CPU(unsigned int, diagnose_trace_depth);
 
-void trace_s390_diagnose_norecursion(int diag_nr)
+void notrace trace_s390_diagnose_norecursion(int diag_nr)
 {
 	unsigned long flags;
 	unsigned int *depth;