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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Fri, 24 Jan 2020 12:22:56 +0100
Message-ID: <CACT4Y+aRk5=7UoPb9zmDm5XL9CcJDv9YnzndjXYtt+3FKd8maw@mail.gmail.com>
Subject: Re: [PATCH v2 1/5] include/linux: Add instrumented.h infrastructure
To:     Marco Elver <elver@google.com>
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Alexander Potapenko <glider@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Daniel Axtens <dja@axtens.net>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@kernel.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Kees Cook <keescook@chromium.org>, cyphar@cyphar.com,
        linux-arch <linux-arch@vger.kernel.org>
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On Tue, Jan 21, 2020 at 5:05 PM 'Marco Elver' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
>
> This adds instrumented.h, which provides generic wrappers for memory
> access instrumentation that the compiler cannot emit for various
> sanitizers. Currently this unifies KASAN and KCSAN instrumentation. In
> future this will also include KMSAN instrumentation.
>
> Note that, copy_{to,from}_user should use special instrumentation, since
> we should be able to instrument both source and destination memory
> accesses if both are kernel memory.
>
> The current patch only instruments the memory access where the address
> is always in kernel space, however, both may in fact be kernel addresses
> when a compat syscall passes an argument allocated in the kernel to a
> real syscall. In a future change, both KASAN and KCSAN should check both
> addresses in such cases, as well as KMSAN will make use of both
> addresses. [It made more sense to provide the completed function
> signature, rather than updating it and changing all locations again at a
> later time.]

Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Marco Elver <elver@google.com>
> Acked-by: Alexander Potapenko <glider@google.com>
> ---
> v2:
> * Simplify header, since we currently do not need pre/post user-copy
>   distinction.
> * Make instrument_copy_{to,from}_user function arguments match
>   copy_{to,from}_user and update rationale in commit message.
> ---
>  include/linux/instrumented.h | 109 +++++++++++++++++++++++++++++++++++
>  1 file changed, 109 insertions(+)
>  create mode 100644 include/linux/instrumented.h
>
> diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
> new file mode 100644
> index 000000000000..43e6ea591975
> --- /dev/null
> +++ b/include/linux/instrumented.h
> @@ -0,0 +1,109 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +/*
> + * This header provides generic wrappers for memory access instrumentation that
> + * the compiler cannot emit for: KASAN, KCSAN.
> + */
> +#ifndef _LINUX_INSTRUMENTED_H
> +#define _LINUX_INSTRUMENTED_H
> +
> +#include <linux/compiler.h>
> +#include <linux/kasan-checks.h>
> +#include <linux/kcsan-checks.h>
> +#include <linux/types.h>
> +
> +/**
> + * instrument_read - instrument regular read access
> + *
> + * Instrument a regular read access. The instrumentation should be inserted
> + * before the actual read happens.
> + *
> + * @ptr address of access
> + * @size size of access
> + */
> +static __always_inline void instrument_read(const volatile void *v, size_t size)
> +{
> +       kasan_check_read(v, size);
> +       kcsan_check_read(v, size);
> +}
> +
> +/**
> + * instrument_write - instrument regular write access
> + *
> + * Instrument a regular write access. The instrumentation should be inserted
> + * before the actual write happens.
> + *
> + * @ptr address of access
> + * @size size of access
> + */
> +static __always_inline void instrument_write(const volatile void *v, size_t size)
> +{
> +       kasan_check_write(v, size);
> +       kcsan_check_write(v, size);
> +}
> +
> +/**
> + * instrument_atomic_read - instrument atomic read access
> + *
> + * Instrument an atomic read access. The instrumentation should be inserted
> + * before the actual read happens.
> + *
> + * @ptr address of access
> + * @size size of access
> + */
> +static __always_inline void instrument_atomic_read(const volatile void *v, size_t size)
> +{
> +       kasan_check_read(v, size);
> +       kcsan_check_atomic_read(v, size);
> +}
> +
> +/**
> + * instrument_atomic_write - instrument atomic write access
> + *
> + * Instrument an atomic write access. The instrumentation should be inserted
> + * before the actual write happens.
> + *
> + * @ptr address of access
> + * @size size of access
> + */
> +static __always_inline void instrument_atomic_write(const volatile void *v, size_t size)
> +{
> +       kasan_check_write(v, size);
> +       kcsan_check_atomic_write(v, size);
> +}
> +
> +/**
> + * instrument_copy_to_user - instrument reads of copy_to_user
> + *
> + * Instrument reads from kernel memory, that are due to copy_to_user (and
> + * variants). The instrumentation must be inserted before the accesses.
> + *
> + * @to destination address
> + * @from source address
> + * @n number of bytes to copy
> + */
> +static __always_inline void
> +instrument_copy_to_user(void __user *to, const void *from, unsigned long n)
> +{
> +       kasan_check_read(from, n);
> +       kcsan_check_read(from, n);
> +}
> +
> +/**
> + * instrument_copy_from_user - instrument writes of copy_from_user
> + *
> + * Instrument writes to kernel memory, that are due to copy_from_user (and
> + * variants). The instrumentation should be inserted before the accesses.
> + *
> + * @to destination address
> + * @from source address
> + * @n number of bytes to copy
> + */
> +static __always_inline void
> +instrument_copy_from_user(const void *to, const void __user *from, unsigned long n)
> +{
> +       kasan_check_write(to, n);
> +       kcsan_check_write(to, n);
> +}
> +
> +#endif /* _LINUX_INSTRUMENTED_H */
> --
> 2.25.0.341.g760bfbb309-goog
>
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