From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8E7AC1B0D9 for ; Tue, 8 Dec 2020 08:37:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1EA123A79 for ; Tue, 8 Dec 2020 08:37:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728419AbgLHIhl (ORCPT ); Tue, 8 Dec 2020 03:37:41 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:23947 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728153AbgLHIhl (ORCPT ); Tue, 8 Dec 2020 03:37:41 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4Cqtp22jKHz9txrh; Tue, 8 Dec 2020 09:36:58 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id 55DLeHf5i1Ko; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4Cqtp21kLPz9txrg; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id E3CE28B7B2; Tue, 8 Dec 2020 09:36:58 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 8WqJmFXaXREg; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: from po17688vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7A7638B7B1; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: by po17688vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 42C7066928; Tue, 8 Dec 2020 08:36:58 +0000 (UTC) Message-Id: <0d37490a067840f53fc5b118869917c0aec9ab87.1607416578.git.christophe.leroy@csgroup.eu> From: Christophe Leroy Subject: [PATCH v3 1/5] powerpc/book3s64/kuap: Improve error reporting with KUAP To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , npiggin@gmail.com, aneesh.kumar@linux.ibm.com Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Date: Tue, 8 Dec 2020 08:36:58 +0000 (UTC) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Aneesh Kumar K.V This partially reverts commit eb232b162446 ("powerpc/book3s64/kuap: Improve error reporting with KUAP") and update the fault handler to print [ 55.022514] Kernel attempted to access user page (7e6725b70000) - exploit attempt? (uid: 0) [ 55.022528] BUG: Unable to handle kernel data access on read at 0x7e6725b70000 [ 55.022533] Faulting instruction address: 0xc000000000e8b9bc [ 55.022540] Oops: Kernel access of bad area, sig: 11 [#1] .... when the kernel access userspace address without unlocking AMR. bad_kuap_fault() is added as part of commit 5e5be3aed230 ("powerpc/mm: Detect bad KUAP faults") to catch userspace access incorrectly blocked by AMR. Hence retain the full stack dump there even with hash translation. Also, add a comment explaining the difference between hash and radix. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Christophe Leroy --- arch/powerpc/include/asm/book3s/32/kup.h | 4 +-- arch/powerpc/include/asm/book3s/64/kup.h | 34 ++++++++++---------- arch/powerpc/include/asm/kup.h | 4 +-- arch/powerpc/include/asm/nohash/32/kup-8xx.h | 4 +-- arch/powerpc/mm/fault.c | 4 +-- 5 files changed, 25 insertions(+), 25 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h index b18cd931e325..32fd4452e960 100644 --- a/arch/powerpc/include/asm/book3s/32/kup.h +++ b/arch/powerpc/include/asm/book3s/32/kup.h @@ -177,8 +177,8 @@ static inline void restore_user_access(unsigned long flags) allow_user_access(to, to, end - addr, KUAP_READ_WRITE); } -static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) +static inline bool +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write) { unsigned long begin = regs->kuap & 0xf0000000; unsigned long end = regs->kuap << 28; diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h index f2e6dd78d5e2..7075c92c320c 100644 --- a/arch/powerpc/include/asm/book3s/64/kup.h +++ b/arch/powerpc/include/asm/book3s/64/kup.h @@ -353,29 +353,29 @@ static inline void set_kuap(unsigned long value) isync(); } -#define RADIX_KUAP_BLOCK_READ UL(0x4000000000000000) -#define RADIX_KUAP_BLOCK_WRITE UL(0x8000000000000000) - static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) + bool is_write) { if (!mmu_has_feature(MMU_FTR_BOOK3S_KUAP)) return false; - - if (radix_enabled()) { - /* - * Will be a storage protection fault. - * Only check the details of AMR[0] - */ - return WARN((regs->kuap & (is_write ? RADIX_KUAP_BLOCK_WRITE : RADIX_KUAP_BLOCK_READ)), - "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read"); - } /* - * We don't want to WARN here because userspace can setup - * keys such that a kernel access to user address can cause - * fault + * For radix this will be a storage protection fault (DSISR_PROTFAULT). + * For hash this will be a key fault (DSISR_KEYFAULT) */ - return !!(error_code & DSISR_KEYFAULT); + /* + * We do have exception table entry, but accessing the + * userspace results in fault. This could be because we + * didn't unlock the AMR or access is denied by userspace + * using a key value that blocks access. We are only interested + * in catching the use case of accessing without unlocking + * the AMR. Hence check for BLOCK_WRITE/READ against AMR. + */ + if (is_write) { + return WARN(((regs->amr & AMR_KUAP_BLOCK_WRITE) == AMR_KUAP_BLOCK_WRITE), + "Bug: Write fault blocked by AMR!"); + } + return WARN(((regs->amr & AMR_KUAP_BLOCK_READ) == AMR_KUAP_BLOCK_READ), + "Bug: Read fault blocked by AMR!"); } static __always_inline void allow_user_access(void __user *to, const void __user *from, diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h index f8ec679bd2de..5a9820c54da9 100644 --- a/arch/powerpc/include/asm/kup.h +++ b/arch/powerpc/include/asm/kup.h @@ -62,8 +62,8 @@ void setup_kuap(bool disabled); #else static inline void setup_kuap(bool disabled) { } -static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) +static inline bool +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write) { return false; } diff --git a/arch/powerpc/include/asm/nohash/32/kup-8xx.h b/arch/powerpc/include/asm/nohash/32/kup-8xx.h index 7bdd9e5b63ed..567cdc557402 100644 --- a/arch/powerpc/include/asm/nohash/32/kup-8xx.h +++ b/arch/powerpc/include/asm/nohash/32/kup-8xx.h @@ -60,8 +60,8 @@ static inline void restore_user_access(unsigned long flags) mtspr(SPRN_MD_AP, flags); } -static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) +static inline bool +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write) { return WARN(!((regs->kuap ^ MD_APG_KUAP) & 0xff000000), "Bug: fault blocked by AP register !"); diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index c91621df0c61..b12595102525 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -210,7 +210,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, return true; } - if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) && + if (!is_exec && address < TASK_SIZE && (error_code & (DSISR_PROTFAULT | DSISR_KEYFAULT)) && !search_exception_tables(regs->nip)) { pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n", address, @@ -227,7 +227,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, // Read/write fault in a valid region (the exception table search passed // above), but blocked by KUAP is bad, it can never succeed. - if (bad_kuap_fault(regs, address, is_write, error_code)) + if (bad_kuap_fault(regs, address, is_write)) return true; // What's left? Kernel fault on user in well defined regions (extable -- 2.25.0 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5E01C433FE for ; Tue, 8 Dec 2020 08:46:11 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D8B7D23A5E for ; Tue, 8 Dec 2020 08:46:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D8B7D23A5E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4Cqv0c2QWkzDqX1 for ; Tue, 8 Dec 2020 19:46:08 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4CqtpC6g09zDqTk for ; Tue, 8 Dec 2020 19:37:05 +1100 (AEDT) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4Cqtp22jKHz9txrh; Tue, 8 Dec 2020 09:36:58 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id 55DLeHf5i1Ko; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4Cqtp21kLPz9txrg; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id E3CE28B7B2; Tue, 8 Dec 2020 09:36:58 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 8WqJmFXaXREg; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: from po17688vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7A7638B7B1; Tue, 8 Dec 2020 09:36:58 +0100 (CET) Received: by po17688vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 42C7066928; Tue, 8 Dec 2020 08:36:58 +0000 (UTC) Message-Id: <0d37490a067840f53fc5b118869917c0aec9ab87.1607416578.git.christophe.leroy@csgroup.eu> From: Christophe Leroy Subject: [PATCH v3 1/5] powerpc/book3s64/kuap: Improve error reporting with KUAP To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , npiggin@gmail.com, aneesh.kumar@linux.ibm.com Date: Tue, 8 Dec 2020 08:36:58 +0000 (UTC) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Aneesh Kumar K.V This partially reverts commit eb232b162446 ("powerpc/book3s64/kuap: Improve error reporting with KUAP") and update the fault handler to print [ 55.022514] Kernel attempted to access user page (7e6725b70000) - exploit attempt? (uid: 0) [ 55.022528] BUG: Unable to handle kernel data access on read at 0x7e6725b70000 [ 55.022533] Faulting instruction address: 0xc000000000e8b9bc [ 55.022540] Oops: Kernel access of bad area, sig: 11 [#1] .... when the kernel access userspace address without unlocking AMR. bad_kuap_fault() is added as part of commit 5e5be3aed230 ("powerpc/mm: Detect bad KUAP faults") to catch userspace access incorrectly blocked by AMR. Hence retain the full stack dump there even with hash translation. Also, add a comment explaining the difference between hash and radix. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Christophe Leroy --- arch/powerpc/include/asm/book3s/32/kup.h | 4 +-- arch/powerpc/include/asm/book3s/64/kup.h | 34 ++++++++++---------- arch/powerpc/include/asm/kup.h | 4 +-- arch/powerpc/include/asm/nohash/32/kup-8xx.h | 4 +-- arch/powerpc/mm/fault.c | 4 +-- 5 files changed, 25 insertions(+), 25 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h index b18cd931e325..32fd4452e960 100644 --- a/arch/powerpc/include/asm/book3s/32/kup.h +++ b/arch/powerpc/include/asm/book3s/32/kup.h @@ -177,8 +177,8 @@ static inline void restore_user_access(unsigned long flags) allow_user_access(to, to, end - addr, KUAP_READ_WRITE); } -static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) +static inline bool +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write) { unsigned long begin = regs->kuap & 0xf0000000; unsigned long end = regs->kuap << 28; diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h index f2e6dd78d5e2..7075c92c320c 100644 --- a/arch/powerpc/include/asm/book3s/64/kup.h +++ b/arch/powerpc/include/asm/book3s/64/kup.h @@ -353,29 +353,29 @@ static inline void set_kuap(unsigned long value) isync(); } -#define RADIX_KUAP_BLOCK_READ UL(0x4000000000000000) -#define RADIX_KUAP_BLOCK_WRITE UL(0x8000000000000000) - static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) + bool is_write) { if (!mmu_has_feature(MMU_FTR_BOOK3S_KUAP)) return false; - - if (radix_enabled()) { - /* - * Will be a storage protection fault. - * Only check the details of AMR[0] - */ - return WARN((regs->kuap & (is_write ? RADIX_KUAP_BLOCK_WRITE : RADIX_KUAP_BLOCK_READ)), - "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read"); - } /* - * We don't want to WARN here because userspace can setup - * keys such that a kernel access to user address can cause - * fault + * For radix this will be a storage protection fault (DSISR_PROTFAULT). + * For hash this will be a key fault (DSISR_KEYFAULT) */ - return !!(error_code & DSISR_KEYFAULT); + /* + * We do have exception table entry, but accessing the + * userspace results in fault. This could be because we + * didn't unlock the AMR or access is denied by userspace + * using a key value that blocks access. We are only interested + * in catching the use case of accessing without unlocking + * the AMR. Hence check for BLOCK_WRITE/READ against AMR. + */ + if (is_write) { + return WARN(((regs->amr & AMR_KUAP_BLOCK_WRITE) == AMR_KUAP_BLOCK_WRITE), + "Bug: Write fault blocked by AMR!"); + } + return WARN(((regs->amr & AMR_KUAP_BLOCK_READ) == AMR_KUAP_BLOCK_READ), + "Bug: Read fault blocked by AMR!"); } static __always_inline void allow_user_access(void __user *to, const void __user *from, diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h index f8ec679bd2de..5a9820c54da9 100644 --- a/arch/powerpc/include/asm/kup.h +++ b/arch/powerpc/include/asm/kup.h @@ -62,8 +62,8 @@ void setup_kuap(bool disabled); #else static inline void setup_kuap(bool disabled) { } -static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) +static inline bool +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write) { return false; } diff --git a/arch/powerpc/include/asm/nohash/32/kup-8xx.h b/arch/powerpc/include/asm/nohash/32/kup-8xx.h index 7bdd9e5b63ed..567cdc557402 100644 --- a/arch/powerpc/include/asm/nohash/32/kup-8xx.h +++ b/arch/powerpc/include/asm/nohash/32/kup-8xx.h @@ -60,8 +60,8 @@ static inline void restore_user_access(unsigned long flags) mtspr(SPRN_MD_AP, flags); } -static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address, - bool is_write, unsigned long error_code) +static inline bool +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write) { return WARN(!((regs->kuap ^ MD_APG_KUAP) & 0xff000000), "Bug: fault blocked by AP register !"); diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index c91621df0c61..b12595102525 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -210,7 +210,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, return true; } - if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) && + if (!is_exec && address < TASK_SIZE && (error_code & (DSISR_PROTFAULT | DSISR_KEYFAULT)) && !search_exception_tables(regs->nip)) { pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n", address, @@ -227,7 +227,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, // Read/write fault in a valid region (the exception table search passed // above), but blocked by KUAP is bad, it can never succeed. - if (bad_kuap_fault(regs, address, is_write, error_code)) + if (bad_kuap_fault(regs, address, is_write)) return true; // What's left? Kernel fault on user in well defined regions (extable -- 2.25.0