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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id n89sm30709882pjc.0.2019.06.22.17.12.37 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 22 Jun 2019 17:12:37 -0700 (PDT) Date: Sat, 22 Jun 2019 17:12:36 -0700 From: Kees Cook To: Matthew Garrett Cc: jmorris@namei.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, David Howells , Matthew Garrett , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo Subject: Re: [PATCH V34 24/29] Lock down perf when in confidentiality mode Message-ID: <201906221710.EB0540F@keescook> References: <20190622000358.19895-1-matthewgarrett@google.com> <20190622000358.19895-25-matthewgarrett@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190622000358.19895-25-matthewgarrett@google.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Jun 21, 2019 at 05:03:53PM -0700, Matthew Garrett wrote: > From: David Howells > > Disallow the use of certain perf facilities that might allow userspace to > access kernel data. > > Signed-off-by: David Howells > Signed-off-by: Matthew Garrett > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > --- > include/linux/security.h | 1 + > kernel/events/core.c | 7 +++++++ > security/lockdown/lockdown.c | 1 + > 3 files changed, 9 insertions(+) > > diff --git a/include/linux/security.h b/include/linux/security.h > index de0d37b1fe79..53ea85889a48 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -98,6 +98,7 @@ enum lockdown_reason { > LOCKDOWN_KCORE, > LOCKDOWN_KPROBES, > LOCKDOWN_BPF_READ, > + LOCKDOWN_PERF, > LOCKDOWN_CONFIDENTIALITY_MAX, > }; > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 72d06e302e99..77f36551756e 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -10731,6 +10731,13 @@ SYSCALL_DEFINE5(perf_event_open, > return -EINVAL; > } > > + err = security_locked_down(LOCKDOWN_PERF); > + if (err && (attr.sample_type & PERF_SAMPLE_REGS_INTR)) > + /* REGS_INTR can leak data, lockdown must prevent this */ > + return err; > + else > + err = 0; > + > /* Only privileged users can get physical addresses */ > if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) && > perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN)) With moar capable() ordering fixed... Reviewed-by: Kees Cook -Kees > diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c > index 2eea2cc13117..a7e75c614416 100644 > --- a/security/lockdown/lockdown.c > +++ b/security/lockdown/lockdown.c > @@ -34,6 +34,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { > [LOCKDOWN_KCORE] = "/proc/kcore access", > [LOCKDOWN_KPROBES] = "use of kprobes", > [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM", > + [LOCKDOWN_PERF] = "unsafe use of perf", > [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", > }; > > -- > 2.22.0.410.gd8fdbe21b5-goog > -- Kees Cook