[PATCH 5.4 176/214] powerpc/perf: Fix crashes with generic_compat_pmu & BHRB

Greg Kroah-Hartman
2020-09-01T16:17:12Z

From: Alexey Kardashevskiy <aik@ozlabs.ru>

commit b460b512417ae9c8b51a3bdcc09020cd6c60ff69 upstream.

The bhrb_filter_map ("The Branch History Rolling Buffer") callback is
only defined in raw CPUs' power_pmu structs. The "architected" CPUs
use generic_compat_pmu, which does not have this callback, and crashes
occur if a user tries to enable branch stack for an event.

This add a NULL pointer check for bhrb_filter_map() which behaves as
if the callback returned an error.

This does not add the same check for config_bhrb() as the only caller
checks for cpuhw->bhrb_users which remains zero if bhrb_filter_map==0.

Fixes: be80e758d0c2 ("powerpc/perf: Add generic compat mode pmu driver")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200602025612.62707-1-aik@ozlabs.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/perf/core-book3s.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)

--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1522,9 +1522,16 @@ nocheck:
ret = 0;
out:
if (has_branch_stack(event)) {
- power_pmu_bhrb_enable(event);
- cpuhw->bhrb_filter = ppmu->bhrb_filter_map(
- event->attr.branch_sample_type);
+ u64 bhrb_filter = -1;
+
+ if (ppmu->bhrb_filter_map)
+ bhrb_filter = ppmu->bhrb_filter_map(
+ event->attr.branch_sample_type);
+
+ if (bhrb_filter != -1) {
+ cpuhw->bhrb_filter = bhrb_filter;
+ power_pmu_bhrb_enable(event);
+ }
}

perf_pmu_enable(event->pmu);
@@ -1846,7 +1853,6 @@ static int power_pmu_event_init(struct p
int n;
int err;
struct cpu_hw_events *cpuhw;
- u64 bhrb_filter;

if (!ppmu)
return -ENOENT;
@@ -1952,7 +1958,10 @@ static int power_pmu_event_init(struct p
err = power_check_constraints(cpuhw, events, cflags, n + 1);

if (has_branch_stack(event)) {
- bhrb_filter = ppmu->bhrb_filter_map(
+ u64 bhrb_filter = -1;
+
+ if (ppmu->bhrb_filter_map)
+ bhrb_filter = ppmu->bhrb_filter_map(
event->attr.branch_sample_type);

if (bhrb_filter == -1) {