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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id g9-20020a633749000000b0053051d50a48sm2177361pgn.79.2023.08.25.15.45.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Aug 2023 15:45:58 -0700 (PDT) Date: Fri, 25 Aug 2023 15:45:57 -0700 From: Kees Cook To: Florent Revest Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, catalin.marinas@arm.com, anshuman.khandual@arm.com, joey.gouly@arm.com, mhocko@suse.com, david@redhat.com, peterx@redhat.com, izbyshev@ispras.ru, broonie@kernel.org, szabolcs.nagy@arm.com, kpsingh@kernel.org, gthelen@google.com, toiwoton@gmail.com Subject: Re: [PATCH v3 5/5] kselftest: vm: Add tests for no-inherit memory-deny-write-execute Message-ID: <202308251538.F716651@keescook> References: <20230704153630.1591122-1-revest@chromium.org> <20230704153630.1591122-6-revest@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230704153630.1591122-6-revest@chromium.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 04, 2023 at 05:36:29PM +0200, Florent Revest wrote: > Add some tests to cover the new PR_MDWE_NO_INHERIT flag of the > PR_SET_MDWE prctl. > > Check that: > - it can't be set without PR_SET_MDWE > - MDWE flags can't be unset > - when set, PR_SET_MDWE doesn't propagate to children I love more self tests! :) > > Signed-off-by: Florent Revest > --- > tools/testing/selftests/mm/mdwe_test.c | 98 ++++++++++++++++++++++++-- > 1 file changed, 92 insertions(+), 6 deletions(-) > > diff --git a/tools/testing/selftests/mm/mdwe_test.c b/tools/testing/selftests/mm/mdwe_test.c > index 91aa9c3099e7..7bfc98bf9baa 100644 > --- a/tools/testing/selftests/mm/mdwe_test.c > +++ b/tools/testing/selftests/mm/mdwe_test.c > @@ -22,6 +22,8 @@ > > TEST(prctl_flags) > { > + EXPECT_LT(prctl(PR_SET_MDWE, PR_MDWE_NO_INHERIT, 0L, 0L, 7L), 0); > + An existing issue, but I think the errno should be checked for each of these... > EXPECT_LT(prctl(PR_SET_MDWE, 7L, 0L, 0L, 0L), 0); > EXPECT_LT(prctl(PR_SET_MDWE, 0L, 7L, 0L, 0L), 0); > EXPECT_LT(prctl(PR_SET_MDWE, 0L, 0L, 7L, 0L), 0); > @@ -33,6 +35,69 @@ TEST(prctl_flags) > EXPECT_LT(prctl(PR_GET_MDWE, 0L, 0L, 0L, 7L), 0); > } > > +FIXTURE(consecutive_prctl_flags) {}; > +FIXTURE_SETUP(consecutive_prctl_flags) {} > +FIXTURE_TEARDOWN(consecutive_prctl_flags) {} > + > +FIXTURE_VARIANT(consecutive_prctl_flags) > +{ > + unsigned long first_flags; > + unsigned long second_flags; > + bool should_work; > +}; > + > +FIXTURE_VARIANT_ADD(consecutive_prctl_flags, same) > +{ > + .first_flags = PR_MDWE_REFUSE_EXEC_GAIN, > + .second_flags = PR_MDWE_REFUSE_EXEC_GAIN, > + .should_work = true, > +}; I think two more variants should be added to get all the combinations: FIXTURE_VARIANT_ADD(consecutive_prctl_no_flags, same) { .first_flags = 0, .second_flags = 0, .should_work = true, }; FIXTURE_VARIANT_ADD(consecutive_prctl_both_flags, same) { .first_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT, .second_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT, .should_work = true, }; > + > +FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_disable_mdwe) > +{ > + .first_flags = PR_MDWE_REFUSE_EXEC_GAIN, > + .second_flags = 0, > + .should_work = false, > +}; > + > +FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_disable_mdwe_no_inherit) > +{ > + .first_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT, > + .second_flags = 0, > + .should_work = false, > +}; > + > +FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_disable_no_inherit) > +{ > + .first_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT, > + .second_flags = PR_MDWE_REFUSE_EXEC_GAIN, > + .should_work = false, > +}; > + > +FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_enable_no_inherit) > +{ > + .first_flags = PR_MDWE_REFUSE_EXEC_GAIN, > + .second_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT, > + .should_work = false, > +}; > + > +TEST_F(consecutive_prctl_flags, two_prctls) > +{ > + int ret; > + > + EXPECT_EQ(prctl(PR_SET_MDWE, variant->first_flags, 0L, 0L, 0L), 0); > + > + ret = prctl(PR_SET_MDWE, variant->second_flags, 0L, 0L, 0L); > + if (variant->should_work) { > + EXPECT_EQ(ret, 0); > + > + ret = prctl(PR_GET_MDWE, 0L, 0L, 0L, 0L); > + ASSERT_EQ(ret, variant->second_flags); > + } else { > + EXPECT_NE(ret, 0); Please test the expected errno value here. > + } > +} > + > FIXTURE(mdwe) > { > void *p; > @@ -45,28 +110,45 @@ FIXTURE_VARIANT(mdwe) > { > bool enabled; > bool forked; > + bool inherit; > }; > > FIXTURE_VARIANT_ADD(mdwe, stock) > { > .enabled = false, > .forked = false, > + .inherit = false, > }; > > FIXTURE_VARIANT_ADD(mdwe, enabled) > { > .enabled = true, > .forked = false, > + .inherit = true, > }; > > -FIXTURE_VARIANT_ADD(mdwe, forked) > +FIXTURE_VARIANT_ADD(mdwe, inherited) > { > .enabled = true, > .forked = true, > + .inherit = true, > }; > > +FIXTURE_VARIANT_ADD(mdwe, not_inherited) > +{ > + .enabled = true, > + .forked = true, > + .inherit = false, > +}; > + > +static bool executable_map_should_fail(const FIXTURE_VARIANT(mdwe) *variant) > +{ > + return variant->enabled && (!variant->forked || variant->inherit); > +} > + > FIXTURE_SETUP(mdwe) > { > + unsigned long mdwe_flags; > int ret, status; > > self->p = NULL; > @@ -76,13 +158,17 @@ FIXTURE_SETUP(mdwe) > if (!variant->enabled) > return; > > - ret = prctl(PR_SET_MDWE, PR_MDWE_REFUSE_EXEC_GAIN, 0L, 0L, 0L); > + mdwe_flags = PR_MDWE_REFUSE_EXEC_GAIN; > + if (!variant->inherit) > + mdwe_flags |= PR_MDWE_NO_INHERIT; > + > + ret = prctl(PR_SET_MDWE, mdwe_flags, 0L, 0L, 0L); > ASSERT_EQ(ret, 0) { > TH_LOG("PR_SET_MDWE failed or unsupported"); > } > > ret = prctl(PR_GET_MDWE, 0L, 0L, 0L, 0L); > - ASSERT_EQ(ret, 1); > + ASSERT_EQ(ret, mdwe_flags); > > if (variant->forked) { > self->pid = fork(); > @@ -113,7 +199,7 @@ TEST_F(mdwe, mmap_READ_EXEC) > TEST_F(mdwe, mmap_WRITE_EXEC) > { > self->p = mmap(NULL, self->size, PROT_WRITE | PROT_EXEC, self->flags, 0, 0); > - if (variant->enabled) { > + if (executable_map_should_fail(variant)) { > EXPECT_EQ(self->p, MAP_FAILED); > } else { > EXPECT_NE(self->p, MAP_FAILED); > @@ -139,7 +225,7 @@ TEST_F(mdwe, mprotect_add_EXEC) > ASSERT_NE(self->p, MAP_FAILED); > > ret = mprotect(self->p, self->size, PROT_READ | PROT_EXEC); > - if (variant->enabled) { > + if (executable_map_should_fail(variant)) { > EXPECT_LT(ret, 0); > } else { > EXPECT_EQ(ret, 0); > @@ -154,7 +240,7 @@ TEST_F(mdwe, mprotect_WRITE_EXEC) > ASSERT_NE(self->p, MAP_FAILED); > > ret = mprotect(self->p, self->size, PROT_WRITE | PROT_EXEC); > - if (variant->enabled) { > + if (executable_map_should_fail(variant)) { > EXPECT_LT(ret, 0); > } else { > EXPECT_EQ(ret, 0); > -- > 2.41.0.255.g8b1d071c50-goog > Otherwise looks good to me! -- Kees Cook