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Message-ID: <CACT4Y+bUvoePVPV+BqU-cwhF6bR41_eaYkr9WLLMYi-2q11JjQ@mail.gmail.com>
Date: Mon, 20 Jan 2020 15:51:48 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: Marco Elver <elver@...gle.com>
Cc: paulmck@...nel.org, Andrey Konovalov <andreyknvl@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
kasan-dev <kasan-dev@...glegroups.com>,
LKML <linux-kernel@...r.kernel.org>,
Mark Rutland <mark.rutland@....com>,
Will Deacon <will@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Boqun Feng <boqun.feng@...il.com>,
Arnd Bergmann <arnd@...db.de>,
Al Viro <viro@...iv.linux.org.uk>,
Christophe Leroy <christophe.leroy@....fr>,
Daniel Axtens <dja@...ens.net>,
Michael Ellerman <mpe@...erman.id.au>,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Christian Brauner <christian.brauner@...ntu.com>,
Daniel Borkmann <daniel@...earbox.net>, cyphar@...har.com,
Kees Cook <keescook@...omium.org>,
linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 5/5] copy_to_user, copy_from_user: Use generic instrumented.h
On Mon, Jan 20, 2020 at 3:19 PM Marco Elver <elver@...gle.com> wrote:
>
> This replaces the KASAN instrumentation with generic instrumentation,
> implicitly adding KCSAN instrumentation support.
>
> For KASAN no functional change is intended.
>
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Marco Elver <elver@...gle.com>
> ---
> include/linux/uaccess.h | 46 +++++++++++++++++++++++++++++------------
> lib/usercopy.c | 14 ++++++++-----
> 2 files changed, 42 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
> index 67f016010aad..d3f2d9a8cae3 100644
> --- a/include/linux/uaccess.h
> +++ b/include/linux/uaccess.h
> @@ -2,9 +2,9 @@
> #ifndef __LINUX_UACCESS_H__
> #define __LINUX_UACCESS_H__
>
> +#include <linux/instrumented.h>
> #include <linux/sched.h>
> #include <linux/thread_info.h>
> -#include <linux/kasan-checks.h>
>
> #define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
>
> @@ -58,18 +58,26 @@
> static __always_inline __must_check unsigned long
> __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
> {
> - kasan_check_write(to, n);
> + unsigned long res;
> +
> check_object_size(to, n, false);
> - return raw_copy_from_user(to, from, n);
> + instrument_copy_from_user_pre(to, n);
> + res = raw_copy_from_user(to, from, n);
> + instrument_copy_from_user_post(to, n, res);
> + return res;
> }
There is also something called strncpy_from_user() that has kasan
instrumentation now:
https://elixir.bootlin.com/linux/v5.5-rc6/source/lib/strncpy_from_user.c#L117
> static __always_inline __must_check unsigned long
> __copy_from_user(void *to, const void __user *from, unsigned long n)
> {
> + unsigned long res;
> +
> might_fault();
> - kasan_check_write(to, n);
> check_object_size(to, n, false);
> - return raw_copy_from_user(to, from, n);
> + instrument_copy_from_user_pre(to, n);
> + res = raw_copy_from_user(to, from, n);
> + instrument_copy_from_user_post(to, n, res);
> + return res;
> }
>
> /**
> @@ -88,18 +96,26 @@ __copy_from_user(void *to, const void __user *from, unsigned long n)
> static __always_inline __must_check unsigned long
> __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
> {
> - kasan_check_read(from, n);
> + unsigned long res;
> +
> check_object_size(from, n, true);
> - return raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_pre(from, n);
> + res = raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_post(from, n, res);
> + return res;
> }
>
> static __always_inline __must_check unsigned long
> __copy_to_user(void __user *to, const void *from, unsigned long n)
> {
> + unsigned long res;
> +
> might_fault();
> - kasan_check_read(from, n);
> check_object_size(from, n, true);
> - return raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_pre(from, n);
> + res = raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_post(from, n, res);
> + return res;
> }
>
> #ifdef INLINE_COPY_FROM_USER
> @@ -109,8 +125,9 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
> unsigned long res = n;
> might_fault();
> if (likely(access_ok(from, n))) {
> - kasan_check_write(to, n);
> + instrument_copy_from_user_pre(to, n);
> res = raw_copy_from_user(to, from, n);
> + instrument_copy_from_user_post(to, n, res);
> }
> if (unlikely(res))
> memset(to + (n - res), 0, res);
> @@ -125,12 +142,15 @@ _copy_from_user(void *, const void __user *, unsigned long);
> static inline __must_check unsigned long
> _copy_to_user(void __user *to, const void *from, unsigned long n)
> {
> + unsigned long res = n;
> +
> might_fault();
> if (access_ok(to, n)) {
> - kasan_check_read(from, n);
> - n = raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_pre(from, n);
> + res = raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_post(from, n, res);
> }
> - return n;
> + return res;
> }
> #else
> extern __must_check unsigned long
> diff --git a/lib/usercopy.c b/lib/usercopy.c
> index cbb4d9ec00f2..1c20d4423b86 100644
> --- a/lib/usercopy.c
> +++ b/lib/usercopy.c
> @@ -1,6 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0
> -#include <linux/uaccess.h>
> #include <linux/bitops.h>
> +#include <linux/instrumented.h>
> +#include <linux/uaccess.h>
>
> /* out-of-line parts */
>
> @@ -10,8 +11,9 @@ unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n
> unsigned long res = n;
> might_fault();
> if (likely(access_ok(from, n))) {
> - kasan_check_write(to, n);
> + instrument_copy_from_user_pre(to, n);
> res = raw_copy_from_user(to, from, n);
> + instrument_copy_from_user_post(to, n, res);
> }
> if (unlikely(res))
> memset(to + (n - res), 0, res);
> @@ -23,12 +25,14 @@ EXPORT_SYMBOL(_copy_from_user);
> #ifndef INLINE_COPY_TO_USER
> unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
> {
> + unsigned long res = n;
> might_fault();
> if (likely(access_ok(to, n))) {
> - kasan_check_read(from, n);
> - n = raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_pre(from, n);
> + res = raw_copy_to_user(to, from, n);
> + instrument_copy_to_user_post(from, n, res);
> }
> - return n;
> + return res;
> }
> EXPORT_SYMBOL(_copy_to_user);
> #endif
> --
> 2.25.0.341.g760bfbb309-goog
>
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