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powercap: intel_rapl: Fix kernel panic during PMU unbind

PATCH RESEND Applied Sumeet Pawnikar 3 participants 3 messages Aug 22 – Aug 24 Power management core

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Sumeet Pawnikar

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#0 lore raw

PATCH RESEND 1/1 powercap: intel_rapl: Fix kernel panic during PMU unbind

From: Sumeet Pawnikar <[email protected]>

rapl_package_add_pmu() fails internally at perf_pmu_register(), and rapl_pmu_update() leaves the global rapl_pmu.pmu structure zero-initialized via memset and returns an error. But any previously probed packages retain has_pmu = true.

When the driver is subsequently unbound or removed, rapl_package_remove_pmu_locked() sees has_pmu == true and unconditionally calls perf_pmu_unregister(&rapl_pmu.pmu) on the zeroed-out structure. This attempts a list_del_rcu() on a NULL list head, immediately causing a kernel panic.

Fix this by checking if the PMU is actually registered before attempting to unregister it.

Signed-off-by Sumeet Pawnikar <[email protected]>
---
 drivers/powercap/intel_rapl_common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
drivers/powercap/intel_rapl_common.c +2 -1
index 1006d183d508..22100f1ca222 100644
@@ -1652,7 +1652,8 @@ void rapl_package_remove_pmu_locked(struct rapl_package *rp)
 			return;
 	}
 
-	perf_pmu_unregister(&rapl_pmu.pmu);
+	if (rapl_pmu.registered)
+		perf_pmu_unregister(&rapl_pmu.pmu);
 	memset(&rapl_pmu, 0, sizeof(struct rapl_pmu));
 }
 EXPORT_SYMBOL_NS_GPL(rapl_package_remove_pmu_locked, "INTEL_RAPL");
Signature · 1 line
2.43.0
Reviewed-by on v1 1/1
#1 lore raw
Quoted 13 lines · Sumeet Pawnikar

From: Sumeet Pawnikar <[email protected]>

rapl_package_add_pmu() fails internally at perf_pmu_register(), and rapl_pmu_update() leaves the global rapl_pmu.pmu structure zero-initialized via memset and returns an error. But any previously probed packages retain has_pmu = true.

When the driver is subsequently unbound or removed, rapl_package_remove_pmu_locked() sees has_pmu == true and unconditionally calls perf_pmu_unregister(&rapl_pmu.pmu) on the zeroed-out structure. This attempts a list_del_rcu() on a NULL list head, immediately causing a kernel panic.

Quoted 4 lines

Fix this by checking if the PMU is actually registered before attempting to unregister it.

Signed-off-by Sumeet Pawnikar <[email protected]>

Looks OK to me, so:

Reviewed-by Abel Vesa <[email protected]>
maintainer Applied
#2 lore raw
Quoted 15 lines · Abel Vesa
Quoted 13 lines · Sumeet Pawnikar

From: Sumeet Pawnikar <[email protected]>

rapl_package_add_pmu() fails internally at perf_pmu_register(), and rapl_pmu_update() leaves the global rapl_pmu.pmu structure zero-initialized via memset and returns an error. But any previously probed packages retain has_pmu = true.

When the driver is subsequently unbound or removed, rapl_package_remove_pmu_locked() sees has_pmu == true and unconditionally calls perf_pmu_unregister(&rapl_pmu.pmu) on the zeroed-out structure. This attempts a list_del_rcu() on a NULL list head, immediately causing a kernel panic.

Quoted 8 lines
Quoted 4 lines

Fix this by checking if the PMU is actually registered before attempting to unregister it.

Signed-off-by Sumeet Pawnikar <[email protected]>

Looks OK to me, so:

Reviewed-by Abel Vesa <[email protected]>

Applied as 7.3-rc material, thanks!