[PATCH 4.13 050/110] s390/perf: fix bug when creating per-thread event

[Greg Kroah-Hartman]

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pu Hou <bjhoupu@xxxxxxxxxxxxxxxxxx>

commit fc3100d64f0ae383ae8d845989103da06d62763b upstream.

A per-thread event could not be created correctly like below:

    perf record --per-thread -e rB0000 -- sleep 1
    Error:
    The sys_perf_event_open() syscall returned with 19 (No such device) for event (rB0000).
    /bin/dmesg may provide additional information.
    No CONFIG_PERF_EVENTS=y kernel support configured?

This bug was introduced by:

    commit c311c797998c1e70eade463dd60b843da4f1a203
    Author: Alexey Dobriyan <adobriyan@xxxxxxxxx>
    Date:   Mon May 8 15:56:15 2017 -0700

    cpumask: make "nr_cpumask_bits" unsigned

If a per-thread event is not attached to any CPU, the cpu field
in struct perf_event is -1. The above commit converts the CPU number
to unsigned int, which result in an illegal CPU number.

Fixes: c311c797998c ("cpumask: make "nr_cpumask_bits" unsigned")
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Acked-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Signed-off-by: Pu Hou <bjhoupu@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/s390/kernel/perf_cpum_sf.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -823,9 +823,12 @@ static int cpumsf_pmu_event_init(struct
 	}
 
 	/* Check online status of the CPU to which the event is pinned */
-	if ((unsigned int)event->cpu >= nr_cpumask_bits ||
-	    (event->cpu >= 0 && !cpu_online(event->cpu)))
-		return -ENODEV;
+	if (event->cpu >= 0) {
+		if ((unsigned int)event->cpu >= nr_cpumask_bits)
+			return -ENODEV;
+		if (!cpu_online(event->cpu))
+			return -ENODEV;
+	}
 
 	/* Force reset of idle/hv excludes regardless of what the
 	 * user requested.