From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 2 Jun 2022 10:14:38 +0300 From: "Dmitry V. Levin" To: devel-kernel@lists.altlinux.org Message-ID: <20220602071438.GA5852@altlinux.org> References: <20220602003100.524482-1-vt@altlinux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220602003100.524482-1-vt@altlinux.org> Subject: Re: [d-kernel] [PATCH] UBUNTU: SAUCE: security, perf: Allow further restriction of perf_event_open X-BeenThere: devel-kernel@lists.altlinux.org X-Mailman-Version: 2.1.12 Precedence: list Reply-To: ALT Linux kernel packages development List-Id: ALT Linux kernel packages development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Jun 2022 07:14:39 -0000 Archived-At: List-Archive: List-Post: On Thu, Jun 02, 2022 at 03:31:00AM +0300, Vitaly Chikunov wrote: > From: Ben Hutchings > > 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 > Signed-off-by: Tim Gardner > [ saf: resolve conflicts with v5.8-rc1 ] > Signed-off-by: Seth Forshee > [ vt: Make it default y. ] > Signed-off-by: Vitaly Chikunov > --- > 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 -------------------------^ -- ldv