Affected: Alpaquita:stream: linux-lts

In the Linux kernel, the following vulnerability has been resolved:

perf/x86: Fix NULL event access and potential PEBS record loss

When intel_pmu_drain_pebs_icl() is called to drain PEBS records, the perf_event_overflow() could be called to process the last PEBS record.

While perf_event_overflow() could trigger the interrupt throttle and stop all events of the group, like what the below call-chain shows.

perf_event_overflow() -> __perf_event_overflow() ->__perf_event_account_interrupt() -> perf_event_throttle_group() -> perf_event_throttle() -> event->pmu->stop() -> x86_pmu_stop()

The side effect of stopping the events is that all corresponding event pointers in cpuc->events[] array are cleared to NULL.

Assume there are two PEBS events (event a and event b) in a group. When intel_pmu_drain_pebs_icl() calls perf_event_overflow() to process the last PEBS record of PEBS event a, interrupt throttle is triggered and all pointers of event a and event b are cleared to NULL. Then intel_pmu_drain_pebs_icl() tries to process the last PEBS record of event b and encounters NULL pointer access.

To avoid this issue, move cpuc->events[] clearing from x86_pmu_stop() to x86_pmu_del(). It's safe since cpuc->active_mask or cpuc->pebs_enabled is always checked before access the event pointer from cpuc->events[].

In the Linux kernel, the following vulnerability has been resolved:

perf/x86: Fix NULL event access and potential PEBS record loss

When intel_pmu_drain_pebs_icl() is called to drain PEBS records, the perf_event_overflow() could be called to process the last PEBS record.

While perf_event_overflow() could trigger the interrupt throttle and stop all events of the group, like what the below call-chain shows.

perf_event_overflow() -> __perf_event_overflow() ->__perf_event_account_interrupt() -> perf_event_throttle_group() -> perf_event_throttle() -> event->pmu->stop() -> x86_pmu_stop()

The side effect of stopping the events is that all corresponding event pointers in cpuc->events[] array are cleared to NULL.

Assume there are two PEBS events (event a and event b) in a group. When intel_pmu_drain_pebs_icl() calls perf_event_overflow() to process the last PEBS record of PEBS event a, interrupt throttle is triggered and all pointers of event a and event b are cleared to NULL. Then intel_pmu_drain_pebs_icl() tries to process the last PEBS record of event b and encounters NULL pointer access.

To avoid this issue, move cpuc->events[] clearing from x86_pmu_stop() to x86_pmu_del(). It's safe since cpuc->active_mask or cpuc->pebs_enabled is always checked before access the event pointer from cpuc->events[].

kernel-devel-6.18.5-1.1 on GA media

Affected: Ubuntu:16.04:LTS: linux-hwe-edge, Ubuntu:18.04:LTS: linux-aws-5.0, Ubuntu:18.04:LTS: linux-aws-5.3, Ubuntu:18.04:LTS: linux-azure, Ubuntu:18.04:LTS: linux-azure-5.3, Ubuntu:18.04:LTS: linux-azure-edge, Ubuntu:18.04:LTS: linux-gcp, Ubuntu:18.04:LTS: linux-gcp-5.3, Ubuntu:18.04:LTS: linux-gke-4.15, Ubuntu:18.04:LTS: linux-gke-5.4 and 97 more

In the Linux kernel, the following vulnerability has been resolved: perf/x86: Fix NULL event access and potential PEBS record loss When intel_pmu_drain_pebs_icl() is called to drain PEBS records, the perf_event_overflow() could be called to process the last PEBS record. While perf_event_overflow() could trigger the interrupt throttle and stop all events of the group, like what the below call-chain shows. perf_event_overflow() -> __perf_event_overflow() ->__perf_event_account_interrupt() -> perf_event_throttle_group() -> perf_event_throttle() -> event->pmu->stop() -> x86_pmu_stop() The side effect of stopping the events is that all corresponding event pointers in cpuc->events[] array are cleared to NULL. Assume there are two PEBS events (event a and event b) in a group. When intel_pmu_drain_pebs_icl() calls perf_event_overflow() to process the last PEBS record of PEBS event a, interrupt throttle is triggered and all pointers of event a and event b are cleared to NULL. Then intel_pmu_drain_pebs_icl() tries to process the last PEBS record of event b and encounters NULL pointer access. To avoid this issue, move cpuc->events[] clearing from x86_pmu_stop() to x86_pmu_del(). It's safe since cpuc->active_mask or cpuc->pebs_enabled is always checked before access the event pointer from cpuc->events[].

Ein Angreifer kann mehrere Schwachstellen im Linux-Kernel ausnutzen, um nicht näher spezifizierte Angriffe durchzuführen, die möglicherweise zu einer Denial-of-Service- Bedingung führen oder eine Speicherbeschädigung verursachen können.