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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> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 495511C002B X-Stat-Signature: 6ym3agu51rdzfdpkuiu1f4fb9rjq6jw6 X-HE-Tag: 1693003560-979348 X-HE-Meta: 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 D+aKkfik 5Y7X1hGi5CuKLyzd686rQOb518e+VjLwJn2ERbywKscRGJEw23cwsU2rseCJCT6EwwZMg+ZEd04cya46Z56mfsVVrUUjvjuE5kpQn4SwfggNE/DMRf6Jo4Iri+LuoFlAa3PpTgajXASe/dkQYMplUELue97OWd7eeF3PtboIuWFNYgCF7LunwjERbugrF0WtZnVIGbAim1niRk7eiIVmLQJT6eN3+lU/Cv7Ecc8Sq9/iyE9lB+cv386P96LKL/ed9NyJlIVP7dDOtGmg+rhEYTFd0D1N4j3phqDnqkui220Eu5AICeaiwuFb9l/pwrHtkR3+FBGu1XgriYPbX8hGRmFmmHbdXKNnNHe2msBE7QW8CHmmlDg6BnTh2gpEep7b2OM2K8SzVEuVkDpibsjk4NgUrLAq7dZo5ee4n X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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