linux-kernel - [PATCH 31/36] arm: Implement thread_struct whitelist for hardened usercopy

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Message-Id: <1515531365-37423-32-git-send-email-keescook@chromium.org>
Date:   Tue,  9 Jan 2018 12:56:00 -0800
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Russell King <linux@...linux.org.uk>,
        Ingo Molnar <mingo@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        linux-arm-kernel@...ts.infradead.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Windsor <dave@...lcore.net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Christoph Lameter <cl@...ux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Laura Abbott <labbott@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Jan Kara <jack@...e.cz>,
        Luis de Bethencourt <luisbg@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Rik van Riel <riel@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-arch@...r.kernel.org,
        netdev@...r.kernel.org, linux-mm@...ck.org,
        kernel-hardening@...ts.openwall.com
Subject: [PATCH 31/36] arm: Implement thread_struct whitelist for hardened usercopy

ARM does not carry FPU state in the thread structure, so it can declare
no usercopy whitelist at all.

Cc: Russell King <linux@...linux.org.uk>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Christian Borntraeger <borntraeger@...ibm.com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc: linux-arm-kernel@...ts.infradead.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/arm/Kconfig                 | 1 +
 arch/arm/include/asm/processor.h | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 51c8df561077..3ea00d65f35d 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -50,6 +50,7 @@ config ARM
 	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
 	select HAVE_ARCH_MMAP_RND_BITS if MMU
 	select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT)
+	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARM_SMCCC if CPU_V7
 	select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 338cbe0a18ef..01a41be58d43 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -45,6 +45,13 @@ struct thread_struct {
 	struct debug_info	debug;
 };
 
+/* Nothing needs to be usercopy-whitelisted from thread_struct. */
+static inline void arch_thread_struct_whitelist(unsigned long *offset,
+						unsigned long *size)
+{
+	*offset = *size = 0;
+}
+
 #define INIT_THREAD  {	}
 
 #define start_thread(regs,pc,sp)					\
-- 
2.7.4