linux-kernel - [PATCH 33/38] arm64: Implement thread_struct whitelist for hardened usercopy

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Date:   Wed, 10 Jan 2018 18:03:05 -0800
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        James Morse <james.morse@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Dave Martin <Dave.Martin@....com>, zijun_hu <zijun_hu@....com>,
        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 33/38] arm64: Implement thread_struct whitelist for hardened usercopy

This whitelists the FPU register state portion of the thread_struct for
copying to userspace, instead of the default entire structure.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Christian Borntraeger <borntraeger@...ibm.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: James Morse <james.morse@....com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc: Dave Martin <Dave.Martin@....com>
Cc: zijun_hu <zijun_hu@....com>
Cc: linux-arm-kernel@...ts.infradead.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/arm64/Kconfig                 | 1 +
 arch/arm64/include/asm/processor.h | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a93339f5178f..c84477e6a884 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -90,6 +90,7 @@ config ARM64
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
 	select HAVE_ARCH_SECCOMP_FILTER
+	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select HAVE_ARCH_VMAP_STACK
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 023cacb946c3..e58a5864ec89 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -113,6 +113,14 @@ struct thread_struct {
 	struct debug_info	debug;		/* debugging */
 };
 
+/* Whitelist the fpsimd_state for copying to userspace. */
+static inline void arch_thread_struct_whitelist(unsigned long *offset,
+						unsigned long *size)
+{
+	*offset = offsetof(struct thread_struct, fpsimd_state);
+	*size = sizeof(struct fpsimd_state);
+}
+
 #ifdef CONFIG_COMPAT
 #define task_user_tls(t)						\
 ({									\
-- 
2.7.4