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Message-Id: <bc53284e2c95fd5b65809a1fb8169d4c1618c61b.1563904656.git.andreyknvl@google.com>
Date: Tue, 23 Jul 2019 19:58:38 +0200
From: Andrey Konovalov <andreyknvl@...gle.com>
To: linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
linux-media@...r.kernel.org, kvm@...r.kernel.org,
linux-kselftest@...r.kernel.org
Cc: Catalin Marinas <catalin.marinas@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Will Deacon <will.deacon@....com>,
Mark Rutland <mark.rutland@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Kees Cook <keescook@...omium.org>,
Yishai Hadas <yishaih@...lanox.com>,
Felix Kuehling <Felix.Kuehling@....com>,
Alexander Deucher <Alexander.Deucher@....com>,
Christian Koenig <Christian.Koenig@....com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Jens Wiklander <jens.wiklander@...aro.org>,
Alex Williamson <alex.williamson@...hat.com>,
Leon Romanovsky <leon@...nel.org>,
Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
Dave Martin <Dave.Martin@....com>,
Khalid Aziz <khalid.aziz@...cle.com>, enh <enh@...gle.com>,
Jason Gunthorpe <jgg@...pe.ca>,
Christoph Hellwig <hch@...radead.org>,
Dmitry Vyukov <dvyukov@...gle.com>,
Kostya Serebryany <kcc@...gle.com>,
Evgeniy Stepanov <eugenis@...gle.com>,
Lee Smith <Lee.Smith@....com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
Jacob Bramley <Jacob.Bramley@....com>,
Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
Robin Murphy <robin.murphy@....com>,
Kevin Brodsky <kevin.brodsky@....com>,
Szabolcs Nagy <Szabolcs.Nagy@....com>,
Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v19 01/15] arm64: untag user pointers in access_ok and __uaccess_mask_ptr
This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.
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.
Note, that this patch only temporarily untags the pointers to perform the
checks, but then passes them as is into the kernel internals.
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@....com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
arch/arm64/include/asm/uaccess.h | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 5a1c32260c1f..a138e3b4f717 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -62,6 +62,8 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
{
unsigned long ret, limit = current_thread_info()->addr_limit;
+ addr = untagged_addr(addr);
+
__chk_user_ptr(addr);
asm volatile(
// A + B <= C + 1 for all A,B,C, in four easy steps:
@@ -215,7 +217,8 @@ 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)
@@ -223,10 +226,11 @@ 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();
--
2.22.0.709.g102302147b-goog
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