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AJvYcCVhjA4IWF/A+OgTm86em79WgiGWol6q/k/wX2WNTDqlfuoyGx+jLwJA4hcZi1fVr8HTTpWaMDOyYA==@kvack.org X-Gm-Message-State: AOJu0YwyAgmNFPqLGuujbTMQgEAvoYCIJnblP/V2ec73Sk20rGb2galB ZyFW26L7mNxvztr51IwYZmfol9t+6Iu1rEEpLePAZ23e9PB1+2bLDgye2ONI8oLpTqcT2lNuBJa UILa65k8/d3lBYG1cMP+sYvsal50= X-Google-Smtp-Source: AGHT+IHECShA4tATBXPqyYtooksdYzBqgSf3Db+mvaXbo971SiRyVKAus92Oc8d2TyY05X7ncNh4AVpr2Hikniy6Nxs= X-Received: by 2002:a05:651c:220e:b0:2fb:51f3:9212 with SMTP id 38308e7fff4ca-2fb51f39559mr31642441fa.6.1728990282008; Tue, 15 Oct 2024 04:04:42 -0700 (PDT) MIME-Version: 1.0 References: <20241011035310.2982017-1-snovitoll@gmail.com> In-Reply-To: From: Sabyrzhan Tasbolatov Date: Tue, 15 Oct 2024 16:05:37 +0500 Message-ID: Subject: Re: [PATCH v6] mm, kasan, kmsan: copy_from/to_kernel_nofault To: akpm@linux-foundation.org Cc: bpf@vger.kernel.org, Andrey Konovalov , dvyukov@google.com, elver@google.com, glider@google.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ryabinin.a.a@gmail.com, syzbot+61123a5daeb9f7454599@syzkaller.appspotmail.com, vincenzo.frascino@arm.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: DA470140004 X-Stat-Signature: 1t1chxm7969sd9qn6gjphmjyuid3ih6k X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1728990278-335141 X-HE-Meta: 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 ZrM9z9y/ ffMU9U9c6Zo6/U2nP8iUy+QSKmbzDJSkcGY9t1A2sbhMY499gSi3gp6ap6jeK5LKd1rBxfIBJXvFBAZyL3DxQQcGaDIvIVp3AKsWdYiFfmTkT5VjGO0IHavcoCpBV0cdY16s9mGfBD9uC2oxPC1N8ZLYn0xzAgmySLUSzwuolpWfkMxLtC7Ct6pppHkHt7+kD7cHKgCd3BLJrzWVtFRVtS1bCMJaQ6E88kKa43xUBWhTIA6pWfMp6MKTMknmZ09Xho7LLlUvKzMaTNlraoRCve6sOyzSBet9hyrpIuGKfIt6rL876lE7juxS/uRM2UwaHU66x3/4L6kco2IS8RGNb0TPVQAojGrg0rV5Yf3aMtvX9nskxztx6NiuuiK+PucshMFYsSvXuxmwzte1MyoMOP0qJFjyuaDAvGO+4J6ICgBPJotfLC8XbeOtQ+67OzRJFkCkRB106Qq0t3kCMfBDQb3ttBuBgvTDHociVE5mlg9f9eceXVft12rc+/B6+Xia/5a740jzb+DM5A9zWMMqBtGXXh5A4QIS32vggqjC1OYZG/9z5K/juoeuxWk0OPiOicnJVuIOobvXEAiBVx5q6ydLef90fpT3ltXGFhGRotOKcUSCCS86y6Xe0LbH0qCvnFEdJUqW+uhOXC4lyeVlgKo4fyw== 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: On Sun, Oct 13, 2024 at 3:45=E2=80=AFAM Andrey Konovalov wrote: > > On Fri, Oct 11, 2024 at 5:52=E2=80=AFAM Sabyrzhan Tasbolatov > wrote: > > > > Instrument copy_from_kernel_nofault() with KMSAN for uninitialized kern= el > > memory check and copy_to_kernel_nofault() with KASAN, KCSAN to detect > > the memory corruption. > > > > syzbot reported that bpf_probe_read_kernel() kernel helper triggered > > KASAN report via kasan_check_range() which is not the expected behaviou= r > > as copy_from_kernel_nofault() is meant to be a non-faulting helper. > > > > Solution is, suggested by Marco Elver, to replace KASAN, KCSAN check in > > copy_from_kernel_nofault() with KMSAN detection of copying uninitilaize= d > > kernel memory. In copy_to_kernel_nofault() we can retain > > instrument_write() explicitly for the memory corruption instrumentation= . > > For future reference: please write commit messages in a way that is > readable standalone. I.e. without obscured references to the > discussions or problems in the previous versions of the patch. It's > fine to give such references in itself, but you need to give enough > context in the commit message to make it understandable without > looking up those discussions. > > > copy_to_kernel_nofault() is tested on x86_64 and arm64 with > > CONFIG_KASAN_SW_TAGS. On arm64 with CONFIG_KASAN_HW_TAGS, > > kunit test currently fails. Need more clarification on it. > > > > Link: https://lore.kernel.org/linux-mm/CANpmjNMAVFzqnCZhEity9cjiqQ9CVN1= X7qeeeAp_6yKjwKo8iw@mail.gmail.com/ > > Reviewed-by: Marco Elver > > Reported-by: syzbot+61123a5daeb9f7454599@syzkaller.appspotmail.com > > Closes: https://syzkaller.appspot.com/bug?extid=3D61123a5daeb9f7454599 > > Reported-by: Andrey Konovalov > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=3D210505 > > Signed-off-by: Sabyrzhan Tasbolatov > > --- > > v2: > > - squashed previous submitted in -mm tree 2 patches based on Linus tree > > v3: > > - moved checks to *_nofault_loop macros per Marco's comments > > - edited the commit message > > v4: > > - replaced Suggested-by with Reviewed-by > > v5: > > - addressed Andrey's comment on deleting CONFIG_KASAN_HW_TAGS check in > > mm/kasan/kasan_test_c.c > > - added explanatory comment in kasan_test_c.c > > - added Suggested-by: Marco Elver back per Andrew's comment. > > v6: > > - deleted checks KASAN_TAG_MIN, KASAN_TAG_KERNEL per Andrey's comment. > > - added empty line before kfree. > > --- > > mm/kasan/kasan_test_c.c | 34 ++++++++++++++++++++++++++++++++++ > > mm/kmsan/kmsan_test.c | 17 +++++++++++++++++ > > mm/maccess.c | 10 ++++++++-- > > 3 files changed, 59 insertions(+), 2 deletions(-) > > > > diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c > > index a181e4780d9d..716f2cac9708 100644 > > --- a/mm/kasan/kasan_test_c.c > > +++ b/mm/kasan/kasan_test_c.c > > @@ -1954,6 +1954,39 @@ static void rust_uaf(struct kunit *test) > > KUNIT_EXPECT_KASAN_FAIL(test, kasan_test_rust_uaf()); > > } > > > > +static void copy_to_kernel_nofault_oob(struct kunit *test) > > +{ > > + char *ptr; > > + char buf[128]; > > + size_t size =3D sizeof(buf); > > + > > + /* This test currently fails with the HW_TAGS mode. > > + * The reason is unknown and needs to be investigated. */ > > + KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_HW_TAGS); > > + > > + ptr =3D kmalloc(size - KASAN_GRANULE_SIZE, GFP_KERNEL); > > + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > > + OPTIMIZER_HIDE_VAR(ptr); > > + > > + /* > > + * We test copy_to_kernel_nofault() to detect corrupted memory t= hat is > > + * being written into the kernel. In contrast, copy_from_kernel_= nofault() > > + * is primarily used in kernel helper functions where the source= address > > + * might be random or uninitialized. Applying KASAN instrumentat= ion to > > + * copy_from_kernel_nofault() could lead to false positives. > > + * By focusing KASAN checks only on copy_to_kernel_nofault(), > > + * we ensure that only valid memory is written to the kernel, > > + * minimizing the risk of kernel corruption while avoiding > > + * false positives in the reverse case. > > + */ > > + KUNIT_EXPECT_KASAN_FAIL(test, > > + copy_to_kernel_nofault(&buf[0], ptr, size)); > > + KUNIT_EXPECT_KASAN_FAIL(test, > > + copy_to_kernel_nofault(ptr, &buf[0], size)); > > + > > + kfree(ptr); > > +} > > + > > static struct kunit_case kasan_kunit_test_cases[] =3D { > > KUNIT_CASE(kmalloc_oob_right), > > KUNIT_CASE(kmalloc_oob_left), > > @@ -2027,6 +2060,7 @@ static struct kunit_case kasan_kunit_test_cases[]= =3D { > > KUNIT_CASE(match_all_not_assigned), > > KUNIT_CASE(match_all_ptr_tag), > > KUNIT_CASE(match_all_mem_tag), > > + KUNIT_CASE(copy_to_kernel_nofault_oob), > > KUNIT_CASE(rust_uaf), > > {} > > }; > > diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c > > index 13236d579eba..9733a22c46c1 100644 > > --- a/mm/kmsan/kmsan_test.c > > +++ b/mm/kmsan/kmsan_test.c > > @@ -640,6 +640,22 @@ static void test_unpoison_memory(struct kunit *tes= t) > > KUNIT_EXPECT_TRUE(test, report_matches(&expect)); > > } > > > > +static void test_copy_from_kernel_nofault(struct kunit *test) > > +{ > > + long ret; > > + char buf[4], src[4]; > > + size_t size =3D sizeof(buf); > > + > > + EXPECTATION_UNINIT_VALUE_FN(expect, "copy_from_kernel_nofault")= ; > > + kunit_info( > > + test, > > + "testing copy_from_kernel_nofault with uninitialized me= mory\n"); > > + > > + ret =3D copy_from_kernel_nofault((char *)&buf[0], (char *)&src[= 0], size); > > + USE(ret); > > + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); > > +} > > + > > static struct kunit_case kmsan_test_cases[] =3D { > > KUNIT_CASE(test_uninit_kmalloc), > > KUNIT_CASE(test_init_kmalloc), > > @@ -664,6 +680,7 @@ static struct kunit_case kmsan_test_cases[] =3D { > > KUNIT_CASE(test_long_origin_chain), > > KUNIT_CASE(test_stackdepot_roundtrip), > > KUNIT_CASE(test_unpoison_memory), > > + KUNIT_CASE(test_copy_from_kernel_nofault), > > {}, > > }; > > > > diff --git a/mm/maccess.c b/mm/maccess.c > > index 518a25667323..3ca55ec63a6a 100644 > > --- a/mm/maccess.c > > +++ b/mm/maccess.c > > @@ -13,9 +13,14 @@ bool __weak copy_from_kernel_nofault_allowed(const v= oid *unsafe_src, > > return true; > > } > > > > +/* > > + * The below only uses kmsan_check_memory() to ensure uninitialized ke= rnel > > + * memory isn't leaked. > > + */ > > #define copy_from_kernel_nofault_loop(dst, src, len, type, err_label) = \ > > while (len >=3D sizeof(type)) { = \ > > - __get_kernel_nofault(dst, src, type, err_label); = \ > > + __get_kernel_nofault(dst, src, type, err_label); = \ > > + kmsan_check_memory(src, sizeof(type)); = \ > > dst +=3D sizeof(type); = \ > > src +=3D sizeof(type); = \ > > len -=3D sizeof(type); = \ > > @@ -49,7 +54,8 @@ EXPORT_SYMBOL_GPL(copy_from_kernel_nofault); > > > > #define copy_to_kernel_nofault_loop(dst, src, len, type, err_label) = \ > > while (len >=3D sizeof(type)) { = \ > > - __put_kernel_nofault(dst, src, type, err_label); = \ > > + __put_kernel_nofault(dst, src, type, err_label); = \ > > + instrument_write(dst, sizeof(type)); = \ > > dst +=3D sizeof(type); = \ > > src +=3D sizeof(type); = \ > > len -=3D sizeof(type); = \ > > -- > > 2.34.1 > > > > Reviewed-by: Andrey Konovalov > Tested-by: Andrey Konovalov > > For KASAN parts. Andrew, Please let me know if the last v6 is ready for -mm tree. Previous version was removed here: https://lore.kernel.org/mm-commits/20241010214955.DBEB7C4CEC5@smtp.kernel.o= rg/ Hopefully, they won't conflict in mm/kasan/kasan_test_c.c per another patch= : https://lore.kernel.org/linux-mm/20241014025701.3096253-3-snovitoll@gmail.c= om/ Thanks > > Thank you!