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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id y198sm21516181pfg.116.2020.07.21.12.06.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2020 12:06:44 -0700 (PDT) Date: Tue, 21 Jul 2020 12:06:43 -0700 From: Kees Cook To: Vitor Massaru Iha Message-ID: <202007211203.6CFE2F19BE@keescook> References: <20200721174036.71072-1-vitor@massaru.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200721174036.71072-1-vitor@massaru.org> Cc: linux-kselftest@vger.kernel.org, brendanhiggins@google.com, linux-kernel@vger.kernel.org, davidgow@google.com, linux-kernel-mentees@lists.linuxfoundation.org, kunit-dev@googlegroups.com Subject: Re: [Linux-kernel-mentees] [PATCH v3] lib: kunit: Provides a userspace memory context when tests are compiled as module X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" On Tue, Jul 21, 2020 at 02:40:36PM -0300, Vitor Massaru Iha wrote: > KUnit test cases run on kthreads, and kthreads don't have an > adddress space (current->mm is NULL), but processes have mm. > > The purpose of this patch is to allow to borrow mm to KUnit kthread > after userspace is brought up, because we know that there are processes > running, at least the process that loaded the module to borrow mm. > > This allows, for example, tests such as user_copy_kunit, which uses > vm_mmap, which needs current->mm. Ah! In the case of kunit starting before there IS a userspace... interesting. > Signed-off-by: Vitor Massaru Iha > --- > v2: > * splitted patch in 3: > - Allows to install and load modules in root filesystem; > - Provides an userspace memory context when tests are compiled > as module; > - Convert test_user_copy to KUnit test; > * added documentation; > * added more explanation; > * added a missed test pointer; > * released mm with mmput(); > v3: > * rebased with last kunit branch > * Please apply this commit from kunit-fixes: > 3f37d14b8a3152441f36b6bc74000996679f0998 > > Documentation/dev-tools/kunit/usage.rst | 14 ++++++++++++++ > include/kunit/test.h | 12 ++++++++++++ > lib/kunit/try-catch.c | 15 ++++++++++++++- > 3 files changed, 40 insertions(+), 1 deletion(-) > --- > diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst > index 3c3fe8b5fecc..9f909157be34 100644 > --- a/Documentation/dev-tools/kunit/usage.rst > +++ b/Documentation/dev-tools/kunit/usage.rst > @@ -448,6 +448,20 @@ We can now use it to test ``struct eeprom_buffer``: > > .. _kunit-on-non-uml: > > +User-space context > +------------------ > + > +I case you need a user-space context, for now this is only possible through typo: In case ... > +tests compiled as a module. And it will be necessary to use a root filesystem > +and uml_utilities. > + > +Example: > + > +.. code-block:: bash > + > + ./tools/testing/kunit/kunit.py run --timeout=60 --uml_rootfs_dir=.uml_rootfs > + > + > KUnit on non-UML architectures > ============================== > > diff --git a/include/kunit/test.h b/include/kunit/test.h > index 59f3144f009a..ae3337139c65 100644 > --- a/include/kunit/test.h > +++ b/include/kunit/test.h > @@ -222,6 +222,18 @@ struct kunit { > * protect it with some type of lock. > */ > struct list_head resources; /* Protected by lock. */ > + /* > + * KUnit test cases run on kthreads, and kthreads don't have an > + * adddress space (current->mm is NULL), but processes have mm. > + * > + * The purpose of this mm_struct is to allow to borrow mm to KUnit kthread > + * after userspace is brought up, because we know that there are processes > + * running, at least the process that loaded the module to borrow mm. > + * > + * This allows, for example, tests such as user_copy_kunit, which uses > + * vm_mmap, which needs current->mm. > + */ > + struct mm_struct *mm; I have a general concern that this will need more careful solving in the future as there are likely to be many tests that need a userspace context to operate sanely. But that's just a note; this solves the specific case now. > }; > > void kunit_init_test(struct kunit *test, const char *name, char *log); > diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c > index 0dd434e40487..d03e2093985b 100644 > --- a/lib/kunit/try-catch.c > +++ b/lib/kunit/try-catch.c > @@ -11,7 +11,8 @@ > #include > #include > #include > - > +#include > +#include > #include "try-catch-impl.h" > > void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch) > @@ -24,8 +25,17 @@ EXPORT_SYMBOL_GPL(kunit_try_catch_throw); > static int kunit_generic_run_threadfn_adapter(void *data) > { > struct kunit_try_catch *try_catch = data; > + struct kunit *test = try_catch->test; > + > + if (test != NULL && test->mm != NULL) > + kthread_use_mm(test->mm); > > try_catch->try(try_catch->context); > + if (test != NULL && test->mm != NULL) { > + kthread_unuse_mm(test->mm); > + mmput(test->mm); > + test->mm = NULL; This mmput() seems unbalanced... see below. > + } > > complete_and_exit(try_catch->try_completion, 0); > } > @@ -65,6 +75,9 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context) > try_catch->context = context; > try_catch->try_completion = &try_completion; > try_catch->try_result = 0; > + > + test->mm = get_task_mm(current); > + > task_struct = kthread_run(kunit_generic_run_threadfn_adapter, > try_catch, > "kunit_try_catch_thread"); Isn't there something that destroys a "struct kunit"? I would expect that to perform the mmput(). Why is it up in the threadfn? > > base-commit: d43c7fb05765152d4d4a39a8ef957c4ea14d8847 > -- > 2.26.2 > -- Kees Cook _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees