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Wed, 02 Oct 2024 22:17:10 -0700 (PDT) Received: from dw-tp ([171.76.83.199]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-71dd9d7e54csm444461b3a.67.2024.10.02.22.17.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Oct 2024 22:17:09 -0700 (PDT) From: Ritesh Harjani (IBM) To: linuxppc-dev@lists.ozlabs.org, kasan-dev@googlegroups.com Cc: Michael Ellerman , Nicholas Piggin , Madhavan Srinivasan , Christophe Leroy , Hari Bathini , "Aneesh Kumar K . V" , Donet Tom , Pavithra Prakash , Nirjhar Roy , LKML , Alexander Potapenko , linux-mm@kvack.org, Heiko Carstens Subject: Re: [RFC v2 01/13] mm/kfence: Add a new kunit test test_use_after_free_read_nofault() In-Reply-To: Date: Thu, 03 Oct 2024 10:36:08 +0530 Message-ID: <87cykhydvj.fsf@gmail.com> References: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 27F2B1A0008 X-Stat-Signature: s8e8tq9awzuyoqozb4zqb77p1o9gagqo X-Rspam-User: X-HE-Tag: 1727932631-912270 X-HE-Meta: U2FsdGVkX1/pcCLlT8y27+KM1yu0UCeXGvH37EEMYW7oMM+wGSwFm7eK9bcieZqhwuDF8gCvSHN5OSXLLI8HBV+JnDVTTJuorT+4Kx9tdLd7fRp4lrbIGiLf8JEigoAy1mhnl53W7YJzQp46ahwBREvPwM+vVUlxEK5mSXgKVUWQMiC+Wj/a9jMOe6OrtHl1rEUNi8EqU3AgtwYXgSzPpziudFXgIKaCPEcZR06zechR2+PwJvPk0oWCgjTl4Ogil3Mz6+MOA6IusuAfeHOzN2/Ycbm2HClSM4VO7rLfJmiFVJQMkc83oDtoSXCNG4BFNat/nN28QNI2pLroSZhoA0Vy4/O1RFwxtpxQk6KukA7GxAM712f8Eks5xLhwJKHqnAXIeU1GqFJRRyXymqnpBGHxu7XeQ5rHaljpmgT+aOY3V0ZzkqOWBsZTQVBYb0qEbPXFJgNbxPv19w8Y5pnXYSDie8sqiwDcJ0O98Fl6M6Z7a3rm0+rtRlKGSLEURmRlyg/+0BqGkzIr7y4t1P/TQiFQfx+U6ujSMJC6JOIjBbtxP9LGZq9+GQk/XUMlb5l+kHnRi2392MiHu72YOErdg5yQXwQX92nKxrw12drcoIH3UuvtQ2kS44aCJ/NV7FRgznCcNcPWSiM+mI/IEzM3iAaSr0w3zEbnlA1tKDKjZs10Mnp19Hzk/E9NMvfhYP89PEDJdSsUvBNj3DnHIBAA1MA7LlfHQ/7lTRb+GMePXweLQZSsQBdxWXc27qWdfMInGdcwtzRhQUlhCNUgdRLurPUlPYC4tPKFN5i5jkPra6gdEQuQ3NKolXRS0Q6g6Rhacv/8KgarDvr9s3bobcNYZaO9X6QSN4h2yuSIXvKRhbSlxv/FUE9d7ke/mr6Lzn/l+mwdwOswguBFnzIfnEAxZa9ebhvR1vQp6NJrc9wCWxTQ25f4U4vg5i+hM3I9HGIg/5x7lr+vI0THk2xBTmE Hh93Ea0v 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 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: List-Subscribe: List-Unsubscribe: Hello Kasan/kfence-devs, Wanted your inputs on this kfence kunit test [PATCH-1] and it's respective powerpc fix [Patch-2]. The commit msgs has a good description of it. I see that the same problem was noticed on s390 as well [1] a while ago. So that makes me believe that maybe we should have a kunit test for the same to make sure all architectures handles this properly. Thoughts? [1]: https://lore.kernel.org/all/20230213183858.1473681-1-hca@linux.ibm.com/ -ritesh "Ritesh Harjani (IBM)" writes: > From: Nirjhar Roy > > Faults from copy_from_kernel_nofault() needs to be handled by fixup > table and should not be handled by kfence. Otherwise while reading > /proc/kcore which uses copy_from_kernel_nofault(), kfence can generate > false negatives. This can happen when /proc/kcore ends up reading an > unmapped address from kfence pool. > > Let's add a testcase to cover this case. > > Co-developed-by: Ritesh Harjani (IBM) > Signed-off-by: Ritesh Harjani (IBM) > Signed-off-by: Nirjhar Roy > Cc: kasan-dev@googlegroups.com > Cc: Alexander Potapenko > Cc: linux-mm@kvack.org > --- > mm/kfence/kfence_test.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c > index 00fd17285285..f65fb182466d 100644 > --- a/mm/kfence/kfence_test.c > +++ b/mm/kfence/kfence_test.c > @@ -383,6 +383,22 @@ static void test_use_after_free_read(struct kunit *test) > KUNIT_EXPECT_TRUE(test, report_matches(&expect)); > } > > +static void test_use_after_free_read_nofault(struct kunit *test) > +{ > + const size_t size = 32; > + char *addr; > + char dst; > + int ret; > + > + setup_test_cache(test, size, 0, NULL); > + addr = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY); > + test_free(addr); > + /* Use after free with *_nofault() */ > + ret = copy_from_kernel_nofault(&dst, addr, 1); > + KUNIT_EXPECT_EQ(test, ret, -EFAULT); > + KUNIT_EXPECT_FALSE(test, report_available()); > +} > + > static void test_double_free(struct kunit *test) > { > const size_t size = 32; > @@ -780,6 +796,7 @@ static struct kunit_case kfence_test_cases[] = { > KFENCE_KUNIT_CASE(test_out_of_bounds_read), > KFENCE_KUNIT_CASE(test_out_of_bounds_write), > KFENCE_KUNIT_CASE(test_use_after_free_read), > + KFENCE_KUNIT_CASE(test_use_after_free_read_nofault), > KFENCE_KUNIT_CASE(test_double_free), > KFENCE_KUNIT_CASE(test_invalid_addr_free), > KFENCE_KUNIT_CASE(test_corruption), > -- > 2.46.0