From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f201.google.com (mail-qk1-f201.google.com [209.85.222.201]) (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 5A39E72 for ; Wed, 13 Oct 2021 18:17:11 +0000 (UTC) Received: by mail-qk1-f201.google.com with SMTP id g25-20020a05620a219900b0045f31ac2119so2525211qka.20 for ; Wed, 13 Oct 2021 11:17:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=7Et8itix18GpyAjahZqPt1V8kIsz34x/KqZyZkJ8saM=; b=ozICM49CE2OWJqCOH9tP80XKMk3vu1AtbDr/v3RLj5sNl9OdewL1mtqBHEkZgm/jre dy7ooHFtMVO0amhWXoZs6i5zgN3Uu37lKHSqW0Bsv8Jmq8R8cVVGoyywDiOFq5XGedI9 194cN1LFqMqQEhmMLr1Eqinsgk33ThbxFdrvVvY1Hx7p2a1ZfdfqxHS0i8dTENOBn/sL b8pYfNQ4mQFPllXmBEgNKGgA/0E1I4lTRrvh83vb/bpCu+nOXD487+XFinwyHZevwJo2 2+/rtj1Cek7q66Z5Ii3mdZXqBBp6cXT/Wz94WgSIowULd2Z76AeAWP3pXXgDJx26oKI+ hEvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=7Et8itix18GpyAjahZqPt1V8kIsz34x/KqZyZkJ8saM=; b=UyfzwLDxU7kzIPmbeb62r2gD7sdnUlNFLOFN4QpM7DFg4+MydxEMy6nIGe+WZtDoye RHK9g+ko5E+QdE8o6hpqW6QHE02kRkUZ2hUNGPb2WrAZvgln9CBXxQ+d48XEYEGIMtkr TwhMN5WtTTEuqmqgoMalQLlgHkQinBb2cjW5BD5hSy5o6j0RJTs5+u0RQgapNXhMALih DROaWX4SGCVGvykWRnfUEW+jQod5QDaQhGVEW0X4tp81ne+JyXcAYEAhEnq0vOYFDTxg koW2fjfaKV1NxCwvDNbCK7dcgTMXnq2lrec3wZRkR5j3IrLMHTy3ha2ljHLTWW7nsmt+ uvRQ== X-Gm-Message-State: AOAM530QVA/+JU7Hw4UwW9XnWrHHYCzN0C66SMxAkQDXj/0uaYu5k/oT BxfnIP0HB5yVwjjoSA7910e6Y2uAUNTvJEaCGUU= X-Google-Smtp-Source: ABdhPJwcoHVQJavUD3ZFgfmM1PTs5OPnXrvBPJgKaJnj/ce2aSdRwx6NsvwguvF8iGXaOvNW1dEloN+G1M/p4J7aauQ= X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:9ea6:6c27:1876:926c]) (user=samitolvanen job=sendgmr) by 2002:a05:622a:394:: with SMTP id j20mr1042103qtx.386.1634149030337; Wed, 13 Oct 2021 11:17:10 -0700 (PDT) Date: Wed, 13 Oct 2021 11:16:47 -0700 In-Reply-To: <20211013181658.1020262-1-samitolvanen@google.com> Message-Id: <20211013181658.1020262-5-samitolvanen@google.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20211013181658.1020262-1-samitolvanen@google.com> X-Developer-Key: i=samitolvanen@google.com; a=openpgp; fpr=35CCFB63B283D6D3AEB783944CB5F6848BBC56EE X-Developer-Signature: v=1; a=openpgp-sha256; l=3814; h=from:subject; bh=c20vs+8oCNIwFtONU4ML5OORlTf8ohrpjgEoh/S//sg=; b=owEB7QES/pANAwAKAUy19oSLvFbuAcsmYgBhZyKYmw2MiX69EDT1JRi2oj1H0ISRQ8X3gMVdZ1nt h4/nvC+JAbMEAAEKAB0WIQQ1zPtjsoPW0663g5RMtfaEi7xW7gUCYWcimAAKCRBMtfaEi7xW7uJ8C/ 98X2JIAb8WoYZ0uzW9SPF07AGAyyiJapAKnuP2YI1/zCaq0VUDo7bRT95fO8VEgNThWznatVDRz268 t12ofjD41BS+qUksuSg0gYEoGCDondtLp0mC8rUcAWGGM0XwZeaZMCdNjy1LHBit2qlaplf45eaObr K1AvDg5YyHfGkG4ZROPn2R0jlO1YKt6RtJ+di6FHHjWP+03CzQ1+K3aH2U0g5OK304fnGDjB3LVoNb xOF06HYXFSdVJMBE7TC19OhUsIuwGqXP+JDAL1JRJ6o+jt+zZdxpqVIOJVcprhyPc3EX/NZSN9MsF/ eH3FU41w/QNEowm0RVHSz2TIhmwOuFJTvrV3m2YF2EE+2GdHZh659rUlJ7VaNJ5mNDmezePqwBX6D6 Ubb4JZLobYZNFtGFZs7bhXOwEgVbZ2TFZrzW+jc0cFHXevmx23gp49PMVdi+5Q+NKAW5ZB1UrJFqTd cp90deW3H7Lmp9E7X99yJwjLa/f14Hc7a+jf170aaiQSA= X-Mailer: git-send-email 2.33.0.1079.g6e70778dc9-goog Subject: [PATCH v5 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB From: Sami Tolvanen To: x86@kernel.org Cc: Kees Cook , Josh Poimboeuf , Peter Zijlstra , Nathan Chancellor , Nick Desaulniers , Sedat Dilek , Steven Rostedt , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sami Tolvanen Content-Type: text/plain; charset="UTF-8" This change introduces the DEFINE_CFI_IMMEDIATE_RETURN_STUB macro, which defines a stub function that immediately returns and when defined in the core kernel, always passes indirect call checking with CONFIG_CFI_CLANG. Note that this macro should only be used when a stub cannot be called using the correct function type. Signed-off-by: Sami Tolvanen Tested-by: Nick Desaulniers Tested-by: Sedat Dilek --- include/asm-generic/vmlinux.lds.h | 11 +++++++++++ include/linux/cfi.h | 13 +++++++++++++ kernel/cfi.c | 24 +++++++++++++++++++++++- 3 files changed, 47 insertions(+), 1 deletion(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index f2984af2b85b..5b77284f7221 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -407,6 +407,16 @@ KEEP(*(.static_call_tramp_key)) \ __stop_static_call_tramp_key = .; +#ifdef CONFIG_CFI_CLANG +#define CFI_EXCLUDED_DATA \ + . = ALIGN(8); \ + __start_cfi_excluded = .; \ + KEEP(*(.cfi_excluded_stubs)) \ + __stop_cfi_excluded = .; +#else +#define CFI_EXCLUDED_DATA +#endif + /* * Allow architectures to handle ro_after_init data on their * own by defining an empty RO_AFTER_INIT_DATA. @@ -430,6 +440,7 @@ __start_rodata = .; \ *(.rodata) *(.rodata.*) \ SCHED_DATA \ + CFI_EXCLUDED_DATA \ RO_AFTER_INIT_DATA /* Read only after init */ \ . = ALIGN(8); \ __start___tracepoints_ptrs = .; \ diff --git a/include/linux/cfi.h b/include/linux/cfi.h index 879744aaa6e0..19f74af8eac2 100644 --- a/include/linux/cfi.h +++ b/include/linux/cfi.h @@ -20,6 +20,17 @@ extern void __cfi_check(uint64_t id, void *ptr, void *diag); #define __CFI_ADDRESSABLE(fn, __attr) \ const void *__cfi_jt_ ## fn __visible __attr = (void *)&fn +/* + * Defines a stub function that returns immediately, and when defined and + * referenced in the core kernel, always passes CFI checking. This should + * be used only for stubs that cannot be called using the correct function + * pointer type, which should be rare. + */ +#define DEFINE_CFI_IMMEDIATE_RETURN_STUB(fn) \ + void fn(void) { return; } \ + const void *__cfi_excl_ ## fn __visible \ + __section(".cfi_excluded_stubs") = (void *)&fn + #ifdef CONFIG_CFI_CLANG_SHADOW extern void cfi_module_add(struct module *mod, unsigned long base_addr); @@ -35,6 +46,8 @@ static inline void cfi_module_remove(struct module *mod, unsigned long base_addr #else /* !CONFIG_CFI_CLANG */ #define __CFI_ADDRESSABLE(fn, __attr) +#define DEFINE_CFI_IMMEDIATE_RETURN_STUB(fn) \ + void fn(void) { return; } #endif /* CONFIG_CFI_CLANG */ diff --git a/kernel/cfi.c b/kernel/cfi.c index 9594cfd1cf2c..8d931089141b 100644 --- a/kernel/cfi.c +++ b/kernel/cfi.c @@ -278,12 +278,34 @@ static inline cfi_check_fn find_module_check_fn(unsigned long ptr) return fn; } +extern unsigned long __start_cfi_excluded[]; +extern unsigned long __stop_cfi_excluded[]; + +static inline bool is_cfi_excluded(unsigned long ptr) +{ + unsigned long *p = __start_cfi_excluded; + + for ( ; p < __stop_cfi_excluded; ++p) + if (*p == ptr) + return true; + + return false; +} + +static void __cfi_pass(uint64_t id, void *ptr, void *diag) +{ +} + static inline cfi_check_fn find_check_fn(unsigned long ptr) { cfi_check_fn fn = NULL; - if (is_kernel_text(ptr)) + if (is_kernel_text(ptr)) { + if (unlikely(is_cfi_excluded(ptr))) + return __cfi_pass; + return __cfi_check; + } /* * Indirect call checks can happen when RCU is not watching. Both -- 2.33.0.1079.g6e70778dc9-goog