From: Catalin Marinas <catalin.marinas@arm.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: 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>,
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,
Jacob Bramley <Jacob.Bramley@arm.com>,
Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
Lee Smith <Lee.Smith@arm.com>, Kostya Serebryany <kcc@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
Evgeniy Stepanov <eugenis@google.com>
Subject: Re: [PATCH 3/6] arm64: untag user addresses in copy_from_user and others
Date: Thu, 26 Apr 2018 16:47:25 +0100 [thread overview]
Message-ID: <20180426154725.74a33tnevvbtqx63@armageddon.cambridge.arm.com> (raw)
In-Reply-To: <949c343a4b02b41b80f324c2b7cd56b75e6a04f3.1524077494.git.andreyknvl@google.com>
On Wed, Apr 18, 2018 at 08:53:12PM +0200, Andrey Konovalov wrote:
> @@ -238,12 +239,15 @@ static inline void uaccess_enable_not_uao(void)
> /*
> * Sanitise a uaccess pointer such that it becomes NULL if above the
> * current addr_limit.
> + * Also untag user pointers that have the top byte tag set.
> */
> #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
> static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
> {
> void __user *safe_ptr;
>
> + ptr = untagged_addr(ptr);
> +
> asm volatile(
> " bics xzr, %1, %2\n"
> " csel %0, %1, xzr, eq\n"
First of all, passing a tagged user pointer throughout the kernel is
safe with uaccess routines but not suitable for find_vma() etc.
With this change, we may have an inconsistent behaviour on the tag
masking, depending on whether the entry code uses __uaccess_mask_ptr()
or not. We could preserve the tag with something like:
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index e66b0fca99c2..ed15bfcbd797 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -244,10 +244,11 @@ 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();
--
Catalin
next prev parent reply other threads:[~2018-04-26 15:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-18 18:53 [PATCH 0/6] arm64: untag user pointers passed to the kernel Andrey Konovalov
2018-04-18 18:53 ` [PATCH 1/6] arm64: add type casts to untagged_addr macro Andrey Konovalov
2018-04-18 18:53 ` Andrey Konovalov
2018-04-18 18:53 ` [PATCH 2/6] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2018-04-18 18:53 ` Andrey Konovalov
2018-04-18 18:53 ` [PATCH 3/6] arm64: untag user addresses in copy_from_user and others Andrey Konovalov
2018-04-26 15:47 ` Catalin Marinas [this message]
2018-05-02 15:29 ` Andrey Konovalov
2018-04-18 18:53 ` Andrey Konovalov
2018-04-18 18:53 ` [PATCH 4/6] mm, arm64: untag user addresses in mm/gup.c Andrey Konovalov
2018-04-26 17:47 ` Catalin Marinas
2018-05-02 14:38 ` Andrey Konovalov
2018-05-02 15:36 ` Kirill A. Shutemov
2018-05-02 17:25 ` Andrey Konovalov
2018-05-03 14:09 ` Andrey Konovalov
2018-05-03 15:24 ` Kirill A. Shutemov
2018-05-03 16:51 ` Andrey Konovalov
2018-05-08 15:11 ` Catalin Marinas
2018-05-11 12:36 ` Andrey Konovalov
2018-04-18 18:53 ` Andrey Konovalov
2018-04-18 18:53 ` [PATCH 5/6] lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user Andrey Konovalov
2018-04-18 18:53 ` Andrey Konovalov
2018-04-18 18:53 ` [PATCH 6/6] arm64: update Documentation/arm64/tagged-pointers.txt Andrey Konovalov
2018-04-18 18:53 ` Andrey Konovalov
2018-04-19 9:33 ` [PATCH 0/6] arm64: untag user pointers passed to the kernel Kirill A. Shutemov
2018-04-25 14:45 ` Andrey Konovalov
2018-04-26 17:56 ` Catalin Marinas
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