linux-kernel - [PATCH] powerpc/perf: Fix ref-counting on the PMU 'vpa

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20250204153527.125491-1-vaibhav@linux.ibm.com>
Date: Tue,  4 Feb 2025 21:05:26 +0530
From: Vaibhav Jain <vaibhav@...ux.ibm.com>
To: linuxppc-dev@...ts.ozlabs.org, kvm-ppc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc: Vaibhav Jain <vaibhav@...ux.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>, atrajeev@...ux.vnet.ibm.com,
        kjain@...ux.ibm.com, disgoel@...ux.ibm.com, hbathini@...ux.ibm.com,
        adubey@...ux.ibm.com, gautam@...ux.ibm.com
Subject: [PATCH] powerpc/perf: Fix ref-counting on the PMU 'vpa_pmu'

Commit 176cda0619b6 ("powerpc/perf: Add perf interface to expose vpa
counters") introduced 'vpa_pmu' to expose Book3s-HV nested APIv2 provided
L1<->L2 context switch latency counters to L1 user-space via
perf-events. However the newly introduced PMU named 'vpa_pmu' doesn't
assign ownership of the PMU to the module 'vpa_pmu'. Consequently the
module 'vpa_pmu' can be unloaded while one of the perf-events are still
active, which can lead to kernel oops and panic of the form below on a
Pseries-LPAR:

BUG: Kernel NULL pointer dereference on read at 0x00000058
<snip>
 NIP [c000000000506cb8] event_sched_out+0x40/0x258
 LR [c00000000050e8a4] __perf_remove_from_context+0x7c/0x2b0
 Call Trace:
 [c00000025fc3fc30] [c00000025f8457a8] 0xc00000025f8457a8 (unreliable)
 [c00000025fc3fc80] [fffffffffffffee0] 0xfffffffffffffee0
 [c00000025fc3fcd0] [c000000000501e70] event_function+0xa8/0x120
<snip>
 Kernel panic - not syncing: Aiee, killing interrupt handler!

Fix this by adding the module ownership to 'vpa_pmu' so that the module
'vpa_pmu' is ref-counted and prevented from being unloaded when perf-events
are initialized.

Fixes: 176cda0619b6 ("powerpc/perf: Add perf interface to expose vpa counters")
Signed-off-by: Vaibhav Jain <vaibhav@...ux.ibm.com>
---
 arch/powerpc/perf/vpa-pmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/perf/vpa-pmu.c b/arch/powerpc/perf/vpa-pmu.c
index 6a5bfd2a13b5..840733468959 100644
--- a/arch/powerpc/perf/vpa-pmu.c
+++ b/arch/powerpc/perf/vpa-pmu.c
@@ -156,6 +156,7 @@ static void vpa_pmu_del(struct perf_event *event, int flags)
 }

 static struct pmu vpa_pmu = {
+	.module		= THIS_MODULE,
 	.task_ctx_nr	= perf_sw_context,
 	.name		= "vpa_pmu",
 	.event_init	= vpa_pmu_event_init,
-- 
2.48.1