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Tue, 08 Oct 2024 12:38:36 -0700 (PDT) MIME-Version: 1.0 References: <20241008101526.2591147-1-snovitoll@gmail.com> In-Reply-To: From: Sabyrzhan Tasbolatov Date: Wed, 9 Oct 2024 00:39:24 +0500 Message-ID: Subject: Re: [PATCH v3] mm, kasan, kmsan: copy_from/to_kernel_nofault To: Marco Elver Cc: akpm@linux-foundation.org, andreyknvl@gmail.com, bpf@vger.kernel.org, dvyukov@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-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 45649C000A X-Stat-Signature: p76o8h58bsawmf8c5nowwx6myn1c5ncd X-HE-Tag: 1728416318-155490 X-HE-Meta: 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 aT/Oh4Qf Ks+vbblJzS+Hd/Te6juLwcqgu+BFLSNtiStWMeIpB8u1ttS6DUHEASdOs2EHkFJ7E4hHxcx/S11HxldNGzgUmTSgkk5S0H1Z805f5TCI3NsHH1OPzMplM29udV3XKjywb1mnwBs1F+oC/bUZQtvCNvBGjIjd0i//GriWNCEofP5sH5L6u/qkuh11FLv2/P1lsQuYyk6QvdldmynIgC8cfz29fL5BmsPlum0NwvABDY9MsPzzwE5Y6mhFYZQOsAyST60ANKJMsvPPELF9ebfQe3/Hrt/bTveqoFdpp7Xhdz+SQ5pUFauaNYlKDvc5/aGLbwy8vKRm4Cum0m1i2AwYW+VNKChSeX+SP1m/XMvcK6DxdO2E8grRZO4BVSBiyEQxFByHJ9Te1TwQDB3c5q83Dk+7lupbCqNMjo8EUFCHvHoagTmqkKkq39/uOQ4DK8w6xerlwC34gM9Esu26ofVcFpLAxjD+U+lwBBersWNAB3fmPOEtB25aj+ALAOx0XpL/fdYSWujh0C+vZxVaFiUEIgVcQoBLJfg+MqFRP8sVbnA8Rp1oi3nG0HoZJV4x/tArQ8JRsmcOhc6dCcydWQBmHfs5pfgsf2zFQIClXljMThFQ7/OJtfVXqC+l//SL/y00UcNV0jdTnsJJdKk8PvN1ckLINxYYwlxeX9u706H8rbPAIl5Q= 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 Tue, Oct 8, 2024 at 4:36=E2=80=AFPM Marco Elver wrote= : > > On Tue, 8 Oct 2024 at 12:14, Sabyrzhan Tasbolatov w= rote: > > > > 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= . > > > > 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 > > - currently, disabled in kunit test. > > I assume you retested. Did you also test the bpf_probe_read_kernel() > false positive no longer appears? I've tested on: - x86_64 with KMSAN - x86_64 with KASAN - arm64 with HW_TAGS -- still failing - arm64 with SW_TAGS Please see the testing result in the following link: https://gist.github.com/novitoll/e2ccb2162340f7f8a63b63ee3e0f9994 I've also tested bpf_probe_read_kernel() in x86_64 KMSAN build, it does trigger KMSAN, though I don't see explicitly copy_from_kernel* in stack frame. AFAIU, it's checked prior to it in text_poke_copy(). Attached the PoC in the comment of the link above: root@syzkaller:/tmp# uname -a Linux syzkaller 6.12.0-rc2-g441b500abd70 #10 SMP PREEMPT_DYNAMIC Wed Oct 9 00:17:59 +05 2024 x86_64 GNU/Linux root@syzkaller:/tmp# ./exploit [*] exploit start [+] program loaded! [ 139.778255] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D [ 139.778846] BUG: KMSAN: uninit-value in bcmp+0x155/0x290 [ 139.779311] bcmp+0x155/0x290 [ 139.779591] __text_poke+0xe2d/0x1120 [ 139.779950] text_poke_copy+0x1e7/0x2b0 [ 139.780297] bpf_arch_text_copy+0x41/0xa0 [ 139.780665] bpf_dispatcher_change_prog+0x12dd/0x16b0 [ 139.781324] bpf_prog_test_run_xdp+0xbf0/0x1d20 [ 139.781898] bpf_prog_test_run+0x5d6/0x9a0 [ 139.782372] __sys_bpf+0x758/0xf10 [ 139.782759] __x64_sys_bpf+0xdd/0x130 [ 139.783178] x64_sys_call+0x1a21/0x4e10 [ 139.783610] do_syscall_64+0xcd/0x1b0 [ 139.784039] entry_SYSCALL_64_after_hwframe+0x67/0x6f [ 139.784597] [ 139.784779] Uninit was created at: [ 139.785197] __alloc_pages_noprof+0x717/0xe70 [ 139.785689] alloc_pages_bulk_noprof+0x17e1/0x20e0 [ 139.786223] alloc_pages_bulk_array_mempolicy_noprof+0x49e/0x5b0 [ 139.786873] __vmalloc_node_range_noprof+0xef2/0x24f0 [ 139.787414] execmem_alloc+0x1ec/0x4c0 [ 139.787841] bpf_jit_alloc_exec+0x3e/0x40 [ 139.788299] bpf_dispatcher_change_prog+0x430/0x16b0 [ 139.788837] bpf_prog_test_run_xdp+0xbf0/0x1d20 [ 139.789324] bpf_prog_test_run+0x5d6/0x9a0 [ 139.789774] __sys_bpf+0x758/0xf10 [ 139.790167] __x64_sys_bpf+0xdd/0x130 [ 139.790580] x64_sys_call+0x1a21/0x4e10 [ 139.791007] do_syscall_64+0xcd/0x1b0 [ 139.791423] entry_SYSCALL_64_after_hwframe+0x67/0x6f > > > Link: https://lore.kernel.org/linux-mm/CANpmjNMAVFzqnCZhEity9cjiqQ9CVN1= X7qeeeAp_6yKjwKo8iw@mail.gmail.com/ > > Suggested-by: Marco Elver > > This looks more reasonable: > > Reviewed-by: Marco Elver > > This looks like the most conservative thing to do for now. Done. > > > 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 > > --- > > mm/kasan/kasan_test_c.c | 27 +++++++++++++++++++++++++++ > > mm/kmsan/kmsan_test.c | 17 +++++++++++++++++ > > mm/maccess.c | 10 ++++++++-- > > 3 files changed, 52 insertions(+), 2 deletions(-) > > > > diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c > > index a181e4780d9d..5cff90f831db 100644 > > --- a/mm/kasan/kasan_test_c.c > > +++ b/mm/kasan/kasan_test_c.c > > @@ -1954,6 +1954,32 @@ 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); > > + > > + /* Not detecting fails currently with HW_TAGS */ > > + 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); > > + > > + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) { > > + /* Check that the returned pointer is tagged. */ > > + KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_M= IN); > > + KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_K= ERNEL); > > + } > > + > > + 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 +2053,7 @@ 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 > >