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From:   Alex Shi <alex.shi@linaro.org>
To:     Marc Zyngier <marc.zyngier@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        stable@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org (moderated list:ARM64 PORT
        (AARCH64 ARCHITECTURE)), linux-kernel@vger.kernel.org (open list)
Cc:     Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH 08/52] arm64: uaccess: consistently check object sizes
Date:   Mon, 26 Feb 2018 16:19:42 +0800
Message-Id: <1519633227-29832-9-git-send-email-alex.shi@linaro.org>
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References: <1519633227-29832-1-git-send-email-alex.shi@linaro.org>
Sender: linux-kernel-owner@vger.kernel.org
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From: Mark Rutland <mark.rutland@arm.com>

commit 76624175dca upstream.

Currently in arm64's copy_{to,from}_user, we only check the
source/destination object size if access_ok() tells us the user access
is permissible.

However, in copy_from_user() we'll subsequently zero any remainder on
the destination object. If we failed the access_ok() check, that applies
to the whole object size, which we didn't check.

To ensure that we catch that case, this patch hoists check_object_size()
to the start of copy_from_user(), matching __copy_from_user() and
__copy_to_user(). To make all of our uaccess copy primitives consistent,
the same is done to copy_to_user().

Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alex Shi <alex.shi@linaro.org>
---
 arch/arm64/include/asm/uaccess.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 94e1457..09c9b59 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -326,9 +326,9 @@ static inline unsigned long __must_check copy_from_user(void *to, const void __u
 {
 	unsigned long res = n;
 	kasan_check_write(to, n);
+	check_object_size(to, n, false);
 
 	if (access_ok(VERIFY_READ, from, n)) {
-		check_object_size(to, n, false);
 		res = __arch_copy_from_user(to, from, n);
 	}
 	if (unlikely(res))
@@ -339,9 +339,9 @@ static inline unsigned long __must_check copy_from_user(void *to, const void __u
 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	kasan_check_read(from, n);
+	check_object_size(from, n, true);
 
 	if (access_ok(VERIFY_WRITE, to, n)) {
-		check_object_size(from, n, true);
 		n = __arch_copy_to_user(to, from, n);
 	}
 	return n;
-- 
2.7.4