s390/cpum_cf: Fix uninitialized warning after backport of ce971233242b

Upstream commit ce971233242b ("s390/cpum_cf: Deny all sampling events by
counter PMU"), backported to 6.6 as commit d660c8d8142e ("s390/cpum_cf:
Deny all sampling events by counter PMU"), implicitly depends on the
unconditional initialization of err to -ENOENT added by upstream
commit aa1ac98268cd ("s390/cpumf: Fix double free on error in
cpumf_pmu_event_init()"). The latter change is missing from 6.6,
resulting in an instance of -Wuninitialized, which is fairly obvious
from looking at the actual diff.

  arch/s390/kernel/perf_cpum_cf.c:858:10: warning: variable 'err' is uninitialized when used here [-Wuninitialized]
    858 |                 return err;
        |                        ^~~

Commit aa1ac98268cd ("s390/cpumf: Fix double free on error in
cpumf_pmu_event_init()") depends on commit c70ca298036c ("perf/core:
Simplify the perf_event_alloc() error path"), which is a part of a much
larger series unsuitable for stable.

Extract the unconditional initialization of err to -ENOENT from
commit aa1ac98268cd ("s390/cpumf: Fix double free on error in
cpumf_pmu_event_init()") and apply it to 6.6 as a standalone change to
resolve the warning.

Fixes: d660c8d8142e ("s390/cpum_cf: Deny all sampling events by counter PMU")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c
index 771e1cb17540dbd0a4c6ca3301210f5578937b9b..e590b4c096253e91a3a65af5a6726bdebbe394ca 100644 (file)
--- a/arch/s390/kernel/perf_cpum_cf.c
+++ b/arch/s390/kernel/perf_cpum_cf.c
@@ -852,7 +852,7 @@ static int cpumf_pmu_event_type(struct perf_event *event)
 static int cpumf_pmu_event_init(struct perf_event *event)
 {
        unsigned int type = event->attr.type;
-       int err;
+       int err = -ENOENT;
 
        if (is_sampling_event(event))   /* No sampling support */
                return err;
@@ -861,8 +861,6 @@ static int cpumf_pmu_event_init(struct perf_event *event)
        else if (event->pmu->type == type)
                /* Registered as unknown PMU */
                err = __hw_perf_event_init(event, cpumf_pmu_event_type(event));
-       else
-               return -ENOENT;
 
        if (unlikely(err) && event->destroy)
                event->destroy(event);