Messages in this thread | | | Subject | Re: [RFC 1/4] perf: Move some access checks later in perf_event_open | From | Tvrtko Ursulin <> | Date | Wed, 27 Jun 2018 10:00:42 +0100 |
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On 26/06/18 18:24, Alexey Budankov wrote: > Hi, > > On 26.06.2018 18:36, Tvrtko Ursulin wrote: >> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com> >> >> 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 <tvrtko.ursulin@intel.com> >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Peter Zijlstra <peterz@infradead.org> >> Cc: Ingo Molnar <mingo@redhat.com> >> Cc: "H. Peter Anvin" <hpa@zytor.com> >> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> >> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> >> Cc: Jiri Olsa <jolsa@redhat.com> >> Cc: Namhyung Kim <namhyung@kernel.org> >> Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com> >> Cc: Andi Kleen <ak@linux.intel.com> >> Cc: Alexey Budankov <alexey.budankov@linux.intel.com> >> Cc: linux-kernel@vger.kernel.org >> Cc: x86@kernel.org >> --- >> 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.
My thinking was for this to be as mechanical (code movement) as possible, but I can consider it.
Regards,
Tvrtko
>> + 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; >> >
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