[d-kernel] [PATCH] UBUNTU: SAUCE: security, perf: Allow further restriction of perf_event_open
Andrey Savchenko
bircoph на altlinux.org
Чт Июн 2 18:58:41 MSK 2022
On Thu, 2 Jun 2022 15:40:38 +0300 Vitaly Chikunov wrote:
> Dmitry,
>
> On Thu, Jun 02, 2022 at 10:14:38AM +0300, Dmitry V. Levin wrote:
> > On Thu, Jun 02, 2022 at 03:31:00AM +0300, Vitaly Chikunov wrote:
> > > From: Ben Hutchings <ben на decadent.org.uk>
> > >
> > > https://lkml.org/lkml/2016/1/11/587
> > >
> > > The GRKERNSEC_PERF_HARDEN feature extracted from grsecurity. Adds the
> > > option to disable perf_event_open() entirely for unprivileged users.
> > > This standalone version doesn't include making the variable read-only
> > > (or renaming it).
> > >
> > > When kernel.perf_event_open is set to 3 (or greater), disallow all
> > ----------------------------------------^
> >
> > > access to performance events by users without CAP_SYS_ADMIN.
> > > Add a Kconfig symbol CONFIG_SECURITY_PERF_EVENTS_RESTRICT that
> > > makes this value the default.
> > >
> > > This is based on a similar feature in grsecurity
> > > (CONFIG_GRKERNSEC_PERF_HARDEN). This version doesn't include making
> > > the variable read-only. It also allows enabling further restriction
> > > at run-time regardless of whether the default is changed.
> > >
> > > Signed-off-by: Ben Hutchings <ben на decadent.org.uk>
> > > Signed-off-by: Tim Gardner <tim.gardner на canonical.com>
> > > [ saf: resolve conflicts with v5.8-rc1 ]
> > > Signed-off-by: Seth Forshee <seth.forshee на canonical.com>
> > > [ vt: Make it default y. ]
> > > Signed-off-by: Vitaly Chikunov <vt на altlinux.org>
> > > ---
> > > include/linux/perf_event.h | 6 ++++++
> > > kernel/events/core.c | 8 ++++++++
> > > security/Kconfig | 10 ++++++++++
> > > 3 files changed, 24 insertions(+)
> > >
> > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > > index 733649184b27..b00607abbcdf 100644
> > > --- a/include/linux/perf_event.h
> > > +++ b/include/linux/perf_event.h
> > > @@ -1342,6 +1342,12 @@ int perf_event_max_stack_handler(struct ctl_table *table, int write,
> > > #define PERF_SECURITY_CPU 1
> > > #define PERF_SECURITY_KERNEL 2
> > > #define PERF_SECURITY_TRACEPOINT 3
> > > +#define PERF_SECURITY_MAX 4
> > ----------------------------------------^
> >
> > > +
> > > +static inline bool perf_paranoid_any(void)
> > > +{
> > > + return sysctl_perf_event_paranoid >= PERF_SECURITY_MAX;
> > > +}
> > >
> > > static inline int perf_is_paranoid(void)
> > > {
> > > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > > index 2d7a23a7507b..15a3b37ae213 100644
> > > --- a/kernel/events/core.c
> > > +++ b/kernel/events/core.c
> > > @@ -414,8 +414,13 @@ static struct kmem_cache *perf_event_cache;
> > > * 0 - disallow raw tracepoint access for unpriv
> > > * 1 - disallow cpu events for unpriv
> > > * 2 - disallow kernel profiling for unpriv
> > > + * 4 - disallow all unpriv perf event use
> > --------^
> >
> > > */
> > > +#ifdef CONFIG_SECURITY_PERF_EVENTS_RESTRICT
> > > +int sysctl_perf_event_paranoid __read_mostly = PERF_SECURITY_MAX;
> > > +#else
> > > int sysctl_perf_event_paranoid __read_mostly = 2;
> > > +#endif
> > >
> > > /* Minimum for 512 kiB + 1 user control page */
> > > int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
> > > @@ -12148,6 +12153,9 @@ SYSCALL_DEFINE5(perf_event_open,
> > > if (err)
> > > return err;
> > >
> > > + if (perf_paranoid_any() && !capable(CAP_SYS_ADMIN))
> > > + return -EACCES;
> > > +
> > > err = perf_copy_attr(attr_uptr, &attr);
> > > if (err)
> > > return err;
> > > diff --git a/security/Kconfig b/security/Kconfig
> > > index 6c7b35c941c7..4861085a2d49 100644
> > > --- a/security/Kconfig
> > > +++ b/security/Kconfig
> > > @@ -19,6 +19,16 @@ config SECURITY_DMESG_RESTRICT
> > >
> > > If you are unsure how to answer this question, answer N.
> > >
> > > +config SECURITY_PERF_EVENTS_RESTRICT
> > > + bool "Restrict unprivileged use of performance events"
> > > + depends on PERF_EVENTS
> > > + default y
> > > + help
> > > + If you say Y here, the kernel.perf_event_paranoid sysctl
> > > + will be set to 3 by default, and no unprivileged use of the
> > -------------------------^
>
> Я это заметил, но, думаю, так надо и оставить.
Можно пояснить зачем? Какие задачи планируется этим решить?
Считается ли нормальным, что профилировать нужно будет под рутом?
Всё же хотелось бы, чтоб пользователь мог полноценно заниматься
разработкой и отладкой приложений.
Best regards,
Andrew Savchenko
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