On Wed, Dec 18, 2019 at 12:25:35PM +0300, Alexey Budankov wrote:
>
> Open access to perf_events monitoring for CAP_SYS_PERFMON privileged
> processes. For backward compatibility reasons access to perf_events
> subsystem remains open for CAP_SYS_ADMIN privileged processes but
> CAP_SYS_ADMIN usage for secure perf_events monitoring is discouraged
> with respect to CAP_SYS_PERFMON capability.
>
> Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
> ---
> include/linux/perf_event.h | 6 +++---
> kernel/events/core.c | 6 +++---
> 2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 34c7c6910026..f46acd69425f 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1285,7 +1285,7 @@ static inline int perf_is_paranoid(void)
>
> static inline int perf_allow_kernel(struct perf_event_attr *attr)
> {
> - if (sysctl_perf_event_paranoid > 1 && !capable(CAP_SYS_ADMIN))
> + if (sysctl_perf_event_paranoid > 1 && !perfmon_capable())
> return -EACCES;
>
> return security_perf_event_open(attr, PERF_SECURITY_KERNEL);
> @@ -1293,7 +1293,7 @@ static inline int perf_allow_kernel(struct perf_event_attr *attr)
>
> static inline int perf_allow_cpu(struct perf_event_attr *attr)
> {
> - if (sysctl_perf_event_paranoid > 0 && !capable(CAP_SYS_ADMIN))
> + if (sysctl_perf_event_paranoid > 0 && !perfmon_capable())
> return -EACCES;
>
> return security_perf_event_open(attr, PERF_SECURITY_CPU);
> @@ -1301,7 +1301,7 @@ static inline int perf_allow_cpu(struct perf_event_attr *attr)
>
> static inline int perf_allow_tracepoint(struct perf_event_attr *attr)
> {
> - if (sysctl_perf_event_paranoid > -1 && !capable(CAP_SYS_ADMIN))
> + if (sysctl_perf_event_paranoid > -1 && !perfmon_capable())
> return -EPERM;
>
> return security_perf_event_open(attr, PERF_SECURITY_TRACEPOINT);
These are OK I suppose.
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 059ee7116008..d9db414f2197 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -9056,7 +9056,7 @@ static int perf_kprobe_event_init(struct perf_event *event)
> if (event->attr.type != perf_kprobe.type)
> return -ENOENT;
>
> - if (!capable(CAP_SYS_ADMIN))
> + if (!perfmon_capable())
> return -EACCES;
>
> /*
This one only allows attaching to already extant kprobes, right? It does
not allow creation of kprobes.
> @@ -9116,7 +9116,7 @@ static int perf_uprobe_event_init(struct perf_event *event)
> if (event->attr.type != perf_uprobe.type)
> return -ENOENT;
>
> - if (!capable(CAP_SYS_ADMIN))
> + if (!perfmon_capable())
> return -EACCES;
>
> /*
Idem, I presume.
> @@ -11157,7 +11157,7 @@ SYSCALL_DEFINE5(perf_event_open,
> }
>
> if (attr.namespaces) {
> - if (!capable(CAP_SYS_ADMIN))
> + if (!perfmon_capable())
> return -EACCES;
> }
And given we basically make the entire kernel observable with this CAP,
busting namespaces shoulnd't be a problem either.
So yeah, I suppose that works.
