On Tue, Sep 10, 2013 at 10:58:12AM +0100, Will Deacon wrote:
> Vince's perf fuzzer uncovered the following issue on Alpha:
>
> Unable to handle kernel paging request at virtual address fffffbfe4e46a0e8
> CPU 0 perf_fuzzer(1278): Oops 0
> pc = [<fffffc000031fbc0>] ra = [<fffffc000031ff54>] ps = 0007 Not tainted
> pc is at alpha_perf_event_set_period+0x60/0xf0
> ra is at alpha_pmu_enable+0x1a4/0x1c0
> v0 = 0000000000000000 t0 = 00000000000fffff t1 = fffffc007b3f5800
> t2 = fffffbff275faa94 t3 = ffffffffc9b9bd89 t4 = fffffbfe4e46a098
> t5 = 0000000000000020 t6 = fffffbfe4e46a0b8 t7 = fffffc007f4c8000
> s0 = 0000000000000000 s1 = fffffc0001b0c018 s2 = fffffc0001b0c020
> s3 = fffffc007b3f5800 s4 = 0000000000000001 s5 = ffffffffc9b9bd85
> s6 = 0000000000000001
> a0 = 0000000000000006 a1 = fffffc007b3f5908 a2 = fffffbfe4e46a098
> a3 = 00000005000108c0 a4 = 0000000000000000 a5 = 0000000000000000
> t8 = 0000000000000001 t9 = 0000000000000001 t10= 0000000027829f6f
> t11= 0000000000000020 pv = fffffc000031fb60 at = fffffc0000950900
> gp = fffffc0000940900 sp = fffffc007f4cbca8
> Disabling lock debugging due to kernel taint
> Trace:
> [<fffffc000031ff54>] alpha_pmu_enable+0x1a4/0x1c0
> [<fffffc000039f4e8>] perf_pmu_enable+0x48/0x60
> [<fffffc00003a0d6c>] __perf_install_in_context+0x15c/0x230
> [<fffffc000039d1f0>] remote_function+0x80/0xa0
> [<fffffc00003a0c10>] __perf_install_in_context+0x0/0x230
> [<fffffc000037b7e4>] smp_call_function_single+0x1b4/0x1d0
> [<fffffc000039bb70>] task_function_call+0x60/0x80
> [<fffffc00003a0c10>] __perf_install_in_context+0x0/0x230
> [<fffffc000039bb44>] task_function_call+0x34/0x80
> [<fffffc000039d3fc>] perf_install_in_context+0x9c/0x150
> [<fffffc00003a0c10>] __perf_install_in_context+0x0/0x230
> [<fffffc00003a5100>] SYSC_perf_event_open+0x360/0xac0
> [<fffffc00003110c4>] entSys+0xa4/0xc0
>
> This is due to the raw event encoding being used as an index directly
> into the ev67_mapping array, rather than being validated against the
> ev67_pmc_event_type enumeration instead. Unlike other architectures,
> which allow raw events to propagate into the hardware counters with
> little interference, the limited number of events on Alpha and the
> strict event <-> counter relationships mean that raw events actually
> correspond to the Linux-specific Alpha events, rather than anything
> defined by the architecture.
>
> This patch adds a new callback to alpha_pmu_t for validating the raw
> event encoding with the Linux event types for the PMU, preventing the
> out-of-bounds array access.
>
> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Cc: Michael Cree <mcree@xxxxxxxxxxxx>
> Cc: Matt Turner <mattst88@xxxxxxxxx>
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Acked-by: Michael Cree <mcree@xxxxxxxxxxxx>
Cheers
Michael.
> ---
> arch/alpha/kernel/perf_event.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/arch/alpha/kernel/perf_event.c b/arch/alpha/kernel/perf_event.c
> index d821b17..c52e7f0 100644
> --- a/arch/alpha/kernel/perf_event.c
> +++ b/arch/alpha/kernel/perf_event.c
> @@ -83,6 +83,8 @@ struct alpha_pmu_t {
> long pmc_left[3];
> /* Subroutine for allocation of PMCs. Enforces constraints. */
> int (*check_constraints)(struct perf_event **, unsigned long *, int);
> + /* Subroutine for checking validity of a raw event for this PMU. */
> + int (*raw_event_valid)(u64 config);
> };
>
> /*
> @@ -203,6 +205,12 @@ success:
> }
>
>
> +static int ev67_raw_event_valid(u64 config)
> +{
> + return config >= EV67_CYCLES && config < EV67_LAST_ET;
> +};
> +
> +
> static const struct alpha_pmu_t ev67_pmu = {
> .event_map = ev67_perfmon_event_map,
> .max_events = ARRAY_SIZE(ev67_perfmon_event_map),
> @@ -211,7 +219,8 @@ static const struct alpha_pmu_t ev67_pmu = {
> .pmc_count_mask = {EV67_PCTR_0_COUNT_MASK, EV67_PCTR_1_COUNT_MASK, 0},
> .pmc_max_period = {(1UL<<20) - 1, (1UL<<20) - 1, 0},
> .pmc_left = {16, 4, 0},
> - .check_constraints = ev67_check_constraints
> + .check_constraints = ev67_check_constraints,
> + .raw_event_valid = ev67_raw_event_valid,
> };
>
>
> @@ -609,7 +618,9 @@ static int __hw_perf_event_init(struct perf_event *event)
> } else if (attr->type == PERF_TYPE_HW_CACHE) {
> return -EOPNOTSUPP;
> } else if (attr->type == PERF_TYPE_RAW) {
> - ev = attr->config & 0xff;
> + if (!alpha_pmu->raw_event_valid(attr->config))
> + return -EINVAL;
> + ev = attr->config;
> } else {
> return -EOPNOTSUPP;
> }
> --
> 1.8.3.2
>
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