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[35.204.162.40]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5e5c7669fd0sm8846503a12.51.2025.03.11.17.21.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Mar 2025 17:21:23 -0700 (PDT) From: jeffxu@chromium.org To: akpm@linux-foundation.org, vbabka@suse.cz, lorenzo.stoakes@oracle.com, Liam.Howlett@Oracle.com, broonie@kernel.org, skhan@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, jorgelo@chromium.org, keescook@chromium.org, pedro.falcato@gmail.com, rdunlap@infradead.org, jannh@google.com, Jeff Xu Subject: [RFC PATCH v1 1/2] selftests/mm: mseal_test: avoid using no-op mprotect Date: Wed, 12 Mar 2025 00:21:16 +0000 Message-ID: <20250312002117.2556240-2-jeffxu@google.com> X-Mailer: git-send-email 2.49.0.rc0.332.g42c0ae87b1-goog In-Reply-To: <20250312002117.2556240-1-jeffxu@google.com> References: <20250312002117.2556240-1-jeffxu@google.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Jeff Xu Modify mseal_tests to avoid using no-op mprotect. The no-op mprotect shall be allowed. Signed-off-by: Jeff Xu Fixes: 4a2dd02b0916 ("mm/mprotect: replace can_modify_mm with can_modify_vma") --- tools/testing/selftests/mm/mseal_test.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c index ad17005521a8..0d4e5d8aeefb 100644 --- a/tools/testing/selftests/mm/mseal_test.c +++ b/tools/testing/selftests/mm/mseal_test.c @@ -677,7 +677,7 @@ static void test_seal_mprotect_two_vma(bool seal) FAIL_TEST_IF_FALSE(!ret); } - ret = sys_mprotect(ptr, page_size * 2, PROT_READ | PROT_WRITE); + ret = sys_mprotect(ptr, page_size * 2, PROT_READ); if (seal) FAIL_TEST_IF_FALSE(ret < 0); else @@ -718,7 +718,7 @@ static void test_seal_mprotect_two_vma_with_split(bool seal) FAIL_TEST_IF_FALSE(!ret); /* the second page is sealed. */ - ret = sys_mprotect(ptr + page_size, page_size, PROT_READ | PROT_WRITE); + ret = sys_mprotect(ptr + page_size, page_size, PROT_READ); if (seal) FAIL_TEST_IF_FALSE(ret < 0); else @@ -873,7 +873,7 @@ static void test_seal_mprotect_split(bool seal) FAIL_TEST_IF_FALSE(!ret); - ret = sys_mprotect(ptr + 2 * page_size, 2 * page_size, PROT_READ); + ret = sys_mprotect(ptr + 2 * page_size, 2 * page_size, PROT_WRITE); if (seal) FAIL_TEST_IF_FALSE(ret < 0); else From patchwork Wed Mar 12 00:21:17 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Jeff Xu X-Patchwork-Id: 14012792 Received: from mail-ed1-f47.google.com (mail-ed1-f47.google.com [209.85.208.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2BE234879B for ; Wed, 12 Mar 2025 00:21:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.47 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741738891; cv=none; b=OFjBWWVPoxmsSWbWfjUzDrmB0iH5W0mrx24pDxwWpu3lBc+VZSpwCbSAnryk9i9gidjab9ghKCYWrdBw03tY8l6Ul6aNH3pPYhR1FCYgW05/tF/en2Uk8SuMkPEySnqkBxSZbdLB/ivA9IbMnWEUajrwaFdpT9nPjCDCtVrORLM= ARC-Message-Signature: i=1; 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[35.204.162.40]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5e5c7669fd0sm8846503a12.51.2025.03.11.17.21.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Mar 2025 17:21:25 -0700 (PDT) From: jeffxu@chromium.org To: akpm@linux-foundation.org, vbabka@suse.cz, lorenzo.stoakes@oracle.com, Liam.Howlett@Oracle.com, broonie@kernel.org, skhan@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, jorgelo@chromium.org, keescook@chromium.org, pedro.falcato@gmail.com, rdunlap@infradead.org, jannh@google.com, Jeff Xu Subject: [RFC PATCH v1 2/2] mseal: allow noop mprotect Date: Wed, 12 Mar 2025 00:21:17 +0000 Message-ID: <20250312002117.2556240-3-jeffxu@google.com> X-Mailer: git-send-email 2.49.0.rc0.332.g42c0ae87b1-goog In-Reply-To: <20250312002117.2556240-1-jeffxu@google.com> References: <20250312002117.2556240-1-jeffxu@google.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Jeff Xu Initially, when mseal was introduced in 6.10, semantically, when a VMA within the specified address range is sealed, the mprotect will be rejected, leaving all of VMA unmodified. However, adding an extra loop to check the mseal flag for every VMA slows things down a bit, therefore in 6.12, this issue was solved by removing can_modify_mm and checking each VMA’s mseal flag directly without an extra loop [1]. This is a semantic change, i.e. partial update is allowed, VMAs can be updated until a sealed VMA is found. The new semantic also means, we could allow mprotect on a sealed VMA if the new attribute of VMA remains the same as the old one. Relaxing this avoids unnecessary impacts for applications that want to seal a particular mapping. Doing this also has no security impact. [1] https://lore.kernel.org/all/20240817-mseal-depessimize-v3-0-d8d2e037df30@gmail.com/ Fixes: 4a2dd02b0916 ("mm/mprotect: replace can_modify_mm with can_modify_vma") Signed-off-by: Jeff Xu --- mm/mprotect.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index 516b1d847e2c..a24d23967aa5 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -613,14 +613,14 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, unsigned long charged = 0; int error; - if (!can_modify_vma(vma)) - return -EPERM; - if (newflags == oldflags) { *pprev = vma; return 0; } + if (!can_modify_vma(vma)) + return -EPERM; + /* * Do PROT_NONE PFN permission checks here when we can still * bail out without undoing a lot of state. This is a rather