Hi,
On 26.06.2018 18:36, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <[email protected]>
>
> To enable per-PMU access controls in a following patch first move all call
> sites of perf_paranoid_kernel() to after the event has been created.
>
> Signed-off-by: Tvrtko Ursulin <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Arnaldo Carvalho de Melo <[email protected]>
> Cc: Alexander Shishkin <[email protected]>
> Cc: Jiri Olsa <[email protected]>
> Cc: Namhyung Kim <[email protected]>
> Cc: Madhavan Srinivasan <[email protected]>
> Cc: Andi Kleen <[email protected]>
> Cc: Alexey Budankov <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> ---
> kernel/events/core.c | 36 ++++++++++++++++++++++--------------
> 1 file changed, 22 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index f490caca9aa4..12de95b0472e 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -10189,10 +10189,6 @@ static int perf_copy_attr(struct perf_event_attr
> __user *uattr,
> */
> attr->branch_sample_type = mask;
> }
> - /* privileged levels capture (kernel, hv): check permissions */
> - if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
> - && perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> - return -EACCES;
> }
>
> if (attr->sample_type & PERF_SAMPLE_REGS_USER) {
> @@ -10409,11 +10405,6 @@ SYSCALL_DEFINE5(perf_event_open,
> if (err)
> return err;
>
> - if (!attr.exclude_kernel) {
> - if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> - return -EACCES;
> - }
> -
> if (attr.namespaces) {
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
> @@ -10427,11 +10418,6 @@ SYSCALL_DEFINE5(perf_event_open,
> return -EINVAL;
> }
>
> - /* Only privileged users can get physical addresses */
> - if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
> - perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> - return -EACCES;
> -
> /*
> * In cgroup mode, the pid argument is used to pass the fd
> * opened to the cgroup directory in cgroupfs. The cpu argument
> @@ -10501,6 +10487,28 @@ SYSCALL_DEFINE5(perf_event_open,
> goto err_cred;
> }
>
> + if (!attr.exclude_kernel) {
> + if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN)) {
> + err = -EACCES;
I would separate this combined permissions check into a function e.g.
static bool perf_test_pmu_paranoid(const struct pmu *pmu, int *err) to avoid
code duplication.
> + goto err_alloc;
> + }
> + }
> +
> + /* Only privileged users can get physical addresses */
> + if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
> + perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN)) {
> + err = -EACCES;
> + goto err_alloc;
> + }
> +
> + /* privileged levels capture (kernel, hv): check permissions */
> + if ((attr.sample_type & PERF_SAMPLE_BRANCH_STACK) &&
> + (attr.branch_sample_type & PERF_SAMPLE_BRANCH_PERM_PLM) &&
> + perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN)) {
> + err = -EACCES;
> + goto err_alloc;
> + }
> +
> if (is_sampling_event(event)) {
> if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
> err = -EOPNOTSUPP;
>
