From patchwork Thu Feb 21 23:44:34 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rick Edgecombe X-Patchwork-Id: 10824921 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DF0F1922 for ; Thu, 21 Feb 2019 23:51:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D0E7831D2C for ; Thu, 21 Feb 2019 23:51:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C43B531D2E; Thu, 21 Feb 2019 23:51:51 +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 E0DC831D2E for ; Thu, 21 Feb 2019 23:51:50 +0000 (UTC) Received: (qmail 32624 invoked by uid 550); 21 Feb 2019 23:51:10 -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 32420 invoked from network); 21 Feb 2019 23:51:08 -0000 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,397,1544515200"; d="scan'208";a="322394815" From: Rick Edgecombe To: Andy Lutomirski , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, Thomas Gleixner , Borislav Petkov , Nadav Amit , Dave Hansen , Peter Zijlstra , linux_dti@icloud.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, akpm@linux-foundation.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, will.deacon@arm.com, ard.biesheuvel@linaro.org, kristen@linux.intel.com, deneen.t.dock@intel.com, Nadav Amit Subject: [PATCH v3 03/20] x86/mm: Save DRs when loading a temporary mm Date: Thu, 21 Feb 2019 15:44:34 -0800 Message-Id: <20190221234451.17632-4-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190221234451.17632-1-rick.p.edgecombe@intel.com> References: <20190221234451.17632-1-rick.p.edgecombe@intel.com> X-Virus-Scanned: ClamAV using ClamSMTP From: Nadav Amit Prevent user watchpoints from mistakenly firing while the temporary mm is being used. As the addresses that of the temporary mm might overlap those of the user-process, this is necessary to prevent wrong signals or worse things from happening. Cc: Andy Lutomirski Signed-off-by: Nadav Amit --- arch/x86/include/asm/mmu_context.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index d684b954f3c0..0d6c72ece750 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -13,6 +13,7 @@ #include #include #include +#include extern atomic64_t last_mm_ctx_id; @@ -358,6 +359,7 @@ static inline unsigned long __get_current_cr3_fast(void) typedef struct { struct mm_struct *prev; + unsigned short bp_enabled : 1; } temp_mm_state_t; /* @@ -380,6 +382,22 @@ static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) lockdep_assert_irqs_disabled(); state.prev = this_cpu_read(cpu_tlbstate.loaded_mm); switch_mm_irqs_off(NULL, mm, current); + + /* + * If breakpoints are enabled, disable them while the temporary mm is + * used. Userspace might set up watchpoints on addresses that are used + * in the temporary mm, which would lead to wrong signals being sent or + * crashes. + * + * Note that breakpoints are not disabled selectively, which also causes + * kernel breakpoints (e.g., perf's) to be disabled. This might be + * undesirable, but still seems reasonable as the code that runs in the + * temporary mm should be short. + */ + state.bp_enabled = hw_breakpoint_active(); + if (state.bp_enabled) + hw_breakpoint_disable(); + return state; } @@ -387,6 +405,13 @@ static inline void unuse_temporary_mm(temp_mm_state_t prev) { lockdep_assert_irqs_disabled(); switch_mm_irqs_off(NULL, prev.prev, current); + + /* + * Restore the breakpoints if they were disabled before the temporary mm + * was loaded. + */ + if (prev.bp_enabled) + hw_breakpoint_restore(); } #endif /* _ASM_X86_MMU_CONTEXT_H */