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From: Andrey Konovalov <andreyknvl@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Mark Rutland <mark.rutland@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andrey Konovalov <andreyknvl@google.com>,
	James Morse <james.morse@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Bart Van Assche <bart.vanassche@wdc.com>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
	Zi Yan <zi.yan@cs.rutgers.edu>,
	linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Kostya Serebryany <kcc@google.com>,
	Evgeniy Stepanov <eugenis@google.com>,
	Lee Smith <Lee.Smith@arm.com>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Chintan Pandya <cpandya@codeaurora.org>
Subject: [PATCH v2 3/6] arm64: untag user addresses in access_ok and __uaccess_mask_ptr
Date: Thu,  3 May 2018 16:15:41 +0200	[thread overview]
Message-ID: <20bddb7a15984ba05eb1d248162a845af246449b.1525356769.git.andreyknvl@google.com> (raw)
In-Reply-To: <cover.1525356769.git.andreyknvl@google.com>
In-Reply-To: <cover.1525356769.git.andreyknvl@google.com>

copy_from_user (and a few other similar functions) are used to copy data
from user memory into the kernel memory or vice versa. Since a user can
provided a tagged pointer to one of the syscalls that use copy_from_user,
we need to correctly handle such pointers.

Do this by untagging user pointers in access_ok and in __uaccess_mask_ptr,
before performing access validity checks.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/uaccess.h | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 2d6451cbaa86..fa7318d3d7d5 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -105,7 +105,8 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
 #define untagged_addr(addr)		\
 	((__typeof__(addr))sign_extend64((__u64)(addr), 55))
 
-#define access_ok(type, addr, size)	__range_ok(addr, size)
+#define access_ok(type, addr, size)	\
+	__range_ok(untagged_addr(addr), size)
 #define user_addr_max			get_fs
 
 #define _ASM_EXTABLE(from, to)						\
@@ -237,7 +238,8 @@ static inline void uaccess_enable_not_uao(void)
 
 /*
  * Sanitise a uaccess pointer such that it becomes NULL if above the
- * current addr_limit.
+ * current addr_limit. In case the pointer is tagged (has the top byte set),
+ * untag the pointer before checking.
  */
 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
@@ -245,10 +247,11 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 	void __user *safe_ptr;
 
 	asm volatile(
-	"	bics	xzr, %1, %2\n"
+	"	bics	xzr, %3, %2\n"
 	"	csel	%0, %1, xzr, eq\n"
 	: "=&r" (safe_ptr)
-	: "r" (ptr), "r" (current_thread_info()->addr_limit)
+	: "r" (ptr), "r" (current_thread_info()->addr_limit),
+	  "r" (untagged_addr(ptr))
 	: "cc");
 
 	csdb();
-- 
2.17.0.441.gb46fe60e1d-goog

  parent reply	other threads:[~2018-05-03 14:15 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-03 14:15 [PATCH v2 0/6] arm64: untag user pointers passed to the kernel Andrey Konovalov
2018-05-03 14:15 ` [PATCH v2 1/6] arm64: add type casts to untagged_addr macro Andrey Konovalov
2018-05-03 14:15 ` [PATCH v2 2/6] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2018-05-03 14:15 ` Andrey Konovalov [this message]
2018-05-03 14:15 ` [PATCH v2 4/6] mm, arm64: untag user addresses in mm/gup.c Andrey Konovalov
2018-05-03 14:15 ` [PATCH v2 5/6] lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user Andrey Konovalov
2018-05-03 14:15 ` [PATCH v2 6/6] arm64: update Documentation/arm64/tagged-pointers.txt Andrey Konovalov

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