From patchwork Tue Apr 17 18:37:33 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 10346471 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B68416039A for ; Tue, 17 Apr 2018 18:39:33 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A355A28615 for ; Tue, 17 Apr 2018 18:39:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 97AB928618; Tue, 17 Apr 2018 18:39:33 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 8D4852861D for ; Tue, 17 Apr 2018 18:39:30 +0000 (UTC) Received: (qmail 26423 invoked by uid 550); 17 Apr 2018 18:38:19 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 26329 invoked from network); 17 Apr 2018 18:38:15 -0000 From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: arnd@arndb.de, catalin.marinas@arm.com, cdall@kernel.org, drjones@redhat.com, kvmarm@lists.cs.columbia.edu, linux-arch@vger.kernel.org, marc.zyngier@arm.com, mark.rutland@arm.com, ramana.radhakrishnan@arm.com, suzuki.poulose@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, awallis@codeaurora.org, kernel-hardening@lists.openwall.com Subject: [PATCHv3 09/11] arm64: perf: strip PAC when unwinding userspace Date: Tue, 17 Apr 2018 19:37:33 +0100 Message-Id: <20180417183735.56985-10-mark.rutland@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20180417183735.56985-1-mark.rutland@arm.com> References: <20180417183735.56985-1-mark.rutland@arm.com> X-Virus-Scanned: ClamAV using ClamSMTP When the kernel is unwinding userspace callchains, we can't expect that the userspace consumer of these callchains has the data necessary to strip the PAC from the stored LR. This patch has the kernel strip the PAC from user stackframes when the in-kernel unwinder is used. This only affects the LR value, and not the FP. This only affects the in-kernel unwinder. When userspace performs unwinding, it is up to userspace to strip PACs as necessary (which can be determined from DWARF information). Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Ramana Radhakrishnan Cc: Will Deacon --- arch/arm64/include/asm/pointer_auth.h | 7 +++++++ arch/arm64/kernel/perf_callchain.c | 5 ++++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h index 5ff141245633..a9ad81791c7f 100644 --- a/arch/arm64/include/asm/pointer_auth.h +++ b/arch/arm64/include/asm/pointer_auth.h @@ -79,6 +79,12 @@ static inline void ptrauth_keys_dup(struct ptrauth_keys *old, */ #define ptrauth_pac_mask() GENMASK(54, VA_BITS) +/* Only valid for EL0 TTBR0 instruction pointers */ +static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr) +{ + return ptr & ~ptrauth_pac_mask(); +} + #define mm_ctx_ptrauth_init(ctx) \ ptrauth_keys_init(&(ctx)->ptrauth_keys) @@ -89,6 +95,7 @@ static inline void ptrauth_keys_dup(struct ptrauth_keys *old, ptrauth_keys_dup(&(oldctx)->ptrauth_keys, &(newctx)->ptrauth_keys) #else +#define ptrauth_strip_insn_pac(lr) (lr) #define mm_ctx_ptrauth_init(ctx) #define mm_ctx_ptrauth_switch(ctx) #define mm_ctx_ptrauth_dup(oldctx, newctx) diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c index bcafd7dcfe8b..928204f6ab08 100644 --- a/arch/arm64/kernel/perf_callchain.c +++ b/arch/arm64/kernel/perf_callchain.c @@ -35,6 +35,7 @@ user_backtrace(struct frame_tail __user *tail, { struct frame_tail buftail; unsigned long err; + unsigned long lr; /* Also check accessibility of one struct frame_tail beyond */ if (!access_ok(VERIFY_READ, tail, sizeof(buftail))) @@ -47,7 +48,9 @@ user_backtrace(struct frame_tail __user *tail, if (err) return NULL; - perf_callchain_store(entry, buftail.lr); + lr = ptrauth_strip_insn_pac(buftail.lr); + + perf_callchain_store(entry, lr); /* * Frame pointers should strictly progress back up the stack