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Message-ID: <CABRcYmLYHf28xNTCs_W2rMYH-78fiyOnhXWsgABUwjHOtvC7qw@mail.gmail.com>
Date: Mon, 28 Aug 2023 16:47:21 +0200
From: Florent Revest <revest@...omium.org>
To: Kees Cook <keescook@...omium.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
akpm@...ux-foundation.org, catalin.marinas@....com,
anshuman.khandual@....com, joey.gouly@....com, mhocko@...e.com,
david@...hat.com, peterx@...hat.com, izbyshev@...ras.ru,
broonie@...nel.org, szabolcs.nagy@....com, kpsingh@...nel.org,
gthelen@...gle.com, toiwoton@...il.com
Subject: Re: [PATCH v3 5/5] kselftest: vm: Add tests for no-inherit memory-deny-write-execute
On Sat, Aug 26, 2023 at 12:45 AM Kees Cook <keescook@...omium.org> wrote:
>
> 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! :)
*Insert here a ridiculously long series of party and dancing emojis* ... :)
> >
> > Signed-off-by: Florent Revest <revest@...omium.org>
> > ---
> > 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...
Makes sense! I'll add a bunch of
EXPECT_EQ(errno, EINVAL);
To every existing line here as part of a previous patch, and modify
this patch to cover errnos in the new test cases too.
> > 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,
> };
Agreed! :)
> > +
> > +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.
Alright!
> > + }
> > +}
> > +
> > 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!
*more happy emojis*
On Sat, Aug 26, 2023 at 12:45 AM Kees Cook <keescook@...omium.org> wrote:
>
> 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 <revest@...omium.org>
> > ---
> > 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
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