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arm64: perf: reject groups spanning multiple HW PMUs
The perf core implicitly rejects events spanning multiple HW PMUs, as in these cases the event->ctx will differ. However this validation is performed after pmu::event_init() is called in perf_init_event(), and thus pmu::event_init() may be called with a group leader from a different HW PMU. The ARM64 PMU driver does not take this fact into account, and when validating groups assumes that it can call to_arm_pmu(event->pmu) for any HW event. When the event in question is from another HW PMU this is wrong, and results in dereferencing garbage. This patch updates the ARM64 PMU driver to first test for and reject events from other PMUs, moving the to_arm_pmu and related logic after this test. Fixes a crash triggered by perf_fuzzer on Linux-4.0-rc2, with a CCI PMU present: Bad mode in Synchronous Abort handler detected, code 0x86000006 -- IABT (current EL) CPU: 0 PID: 1371 Comm: perf_fuzzer Not tainted 3.19.0+ #249 Hardware name: V2F-1XV7 Cortex-A53x2 SMM (DT) task: ffffffc07c73a280 ti: ffffffc07b0a0000 task.ti: ffffffc07b0a0000 PC is at 0x0 LR is at validate_event+0x90/0xa8 pc : [<0000000000000000>] lr : [<ffffffc000090228>] pstate: 00000145 sp : ffffffc07b0a3ba0 [< (null)>] (null) [<ffffffc0000907d8>] armpmu_event_init+0x174/0x3cc [<ffffffc00015d870>] perf_try_init_event+0x34/0x70 [<ffffffc000164094>] perf_init_event+0xe0/0x10c [<ffffffc000164348>] perf_event_alloc+0x288/0x358 [<ffffffc000164c5c>] SyS_perf_event_open+0x464/0x98c Code: bad PC value Also cleans up the code to use the arm_pmu only when we know that we are dealing with an arm pmu event. Cc: Will Deacon <firstname.lastname@example.org> Acked-by: Mark Rutland <email@example.com> Acked-by: Peter Ziljstra (Intel) <firstname.lastname@example.org> Signed-off-by: Suzuki K. Poulose <email@example.com> Signed-off-by: Will Deacon <firstname.lastname@example.org>
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