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    Subject[PATCH v4 03/45] instrumented.h: allow instrumenting both sides of copy_from_user()
    From
    Introduce instrument_copy_from_user_before() and
    instrument_copy_from_user_after() hooks to be invoked before and after
    the call to copy_from_user().

    KASAN and KCSAN will be only using instrument_copy_from_user_before(),
    but for KMSAN we'll need to insert code after copy_from_user().

    Signed-off-by: Alexander Potapenko <glider@google.com>
    ---
    v4:
    -- fix _copy_from_user_key() in arch/s390/lib/uaccess.c (Reported-by:
    kernel test robot <lkp@intel.com>)

    Link: https://linux-review.googlesource.com/id/I855034578f0b0f126734cbd734fb4ae1d3a6af99
    ---
    arch/s390/lib/uaccess.c | 3 ++-
    include/linux/instrumented.h | 21 +++++++++++++++++++--
    include/linux/uaccess.h | 19 ++++++++++++++-----
    lib/iov_iter.c | 9 ++++++---
    lib/usercopy.c | 3 ++-
    5 files changed, 43 insertions(+), 12 deletions(-)

    diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c
    index d7b3b193d1088..58033dfcb6d45 100644
    --- a/arch/s390/lib/uaccess.c
    +++ b/arch/s390/lib/uaccess.c
    @@ -81,8 +81,9 @@ unsigned long _copy_from_user_key(void *to, const void __user *from,

    might_fault();
    if (!should_fail_usercopy()) {
    - instrument_copy_from_user(to, from, n);
    + instrument_copy_from_user_before(to, from, n);
    res = raw_copy_from_user_key(to, from, n, key);
    + instrument_copy_from_user_after(to, from, n, res);
    }
    if (unlikely(res))
    memset(to + (n - res), 0, res);
    diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
    index 42faebbaa202a..ee8f7d17d34f5 100644
    --- a/include/linux/instrumented.h
    +++ b/include/linux/instrumented.h
    @@ -120,7 +120,7 @@ instrument_copy_to_user(void __user *to, const void *from, unsigned long n)
    }

    /**
    - * instrument_copy_from_user - instrument writes of copy_from_user
    + * instrument_copy_from_user_before - add instrumentation before 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.
    @@ -130,10 +130,27 @@ instrument_copy_to_user(void __user *to, const void *from, unsigned long n)
    * @n number of bytes to copy
    */
    static __always_inline void
    -instrument_copy_from_user(const void *to, const void __user *from, unsigned long n)
    +instrument_copy_from_user_before(const void *to, const void __user *from, unsigned long n)
    {
    kasan_check_write(to, n);
    kcsan_check_write(to, n);
    }

    +/**
    + * instrument_copy_from_user_after - add instrumentation after copy_from_user
    + *
    + * Instrument writes to kernel memory, that are due to copy_from_user (and
    + * variants). The instrumentation should be inserted after the accesses.
    + *
    + * @to destination address
    + * @from source address
    + * @n number of bytes to copy
    + * @left number of bytes not copied (as returned by copy_from_user)
    + */
    +static __always_inline void
    +instrument_copy_from_user_after(const void *to, const void __user *from,
    + unsigned long n, unsigned long left)
    +{
    +}
    +
    #endif /* _LINUX_INSTRUMENTED_H */
    diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
    index 5a328cf02b75e..da16e96680cf1 100644
    --- a/include/linux/uaccess.h
    +++ b/include/linux/uaccess.h
    @@ -58,20 +58,28 @@
    static __always_inline __must_check unsigned long
    __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
    {
    - instrument_copy_from_user(to, from, n);
    + unsigned long res;
    +
    + instrument_copy_from_user_before(to, from, n);
    check_object_size(to, n, false);
    - return raw_copy_from_user(to, from, n);
    + res = raw_copy_from_user(to, from, n);
    + instrument_copy_from_user_after(to, from, n, res);
    + return res;
    }

    static __always_inline __must_check unsigned long
    __copy_from_user(void *to, const void __user *from, unsigned long n)
    {
    + unsigned long res;
    +
    might_fault();
    + instrument_copy_from_user_before(to, from, n);
    if (should_fail_usercopy())
    return n;
    - instrument_copy_from_user(to, from, n);
    check_object_size(to, n, false);
    - return raw_copy_from_user(to, from, n);
    + res = raw_copy_from_user(to, from, n);
    + instrument_copy_from_user_after(to, from, n, res);
    + return res;
    }

    /**
    @@ -115,8 +123,9 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
    unsigned long res = n;
    might_fault();
    if (!should_fail_usercopy() && likely(access_ok(from, n))) {
    - instrument_copy_from_user(to, from, n);
    + instrument_copy_from_user_before(to, from, n);
    res = raw_copy_from_user(to, from, n);
    + instrument_copy_from_user_after(to, from, n, res);
    }
    if (unlikely(res))
    memset(to + (n - res), 0, res);
    diff --git a/lib/iov_iter.c b/lib/iov_iter.c
    index 0b64695ab632f..fe5d169314dbf 100644
    --- a/lib/iov_iter.c
    +++ b/lib/iov_iter.c
    @@ -159,13 +159,16 @@ static int copyout(void __user *to, const void *from, size_t n)

    static int copyin(void *to, const void __user *from, size_t n)
    {
    + size_t res = n;
    +
    if (should_fail_usercopy())
    return n;
    if (access_ok(from, n)) {
    - instrument_copy_from_user(to, from, n);
    - n = raw_copy_from_user(to, from, n);
    + instrument_copy_from_user_before(to, from, n);
    + res = raw_copy_from_user(to, from, n);
    + instrument_copy_from_user_after(to, from, n, res);
    }
    - return n;
    + return res;
    }

    static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
    diff --git a/lib/usercopy.c b/lib/usercopy.c
    index 7413dd300516e..1505a52f23a01 100644
    --- a/lib/usercopy.c
    +++ b/lib/usercopy.c
    @@ -12,8 +12,9 @@ unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n
    unsigned long res = n;
    might_fault();
    if (!should_fail_usercopy() && likely(access_ok(from, n))) {
    - instrument_copy_from_user(to, from, n);
    + instrument_copy_from_user_before(to, from, n);
    res = raw_copy_from_user(to, from, n);
    + instrument_copy_from_user_after(to, from, n, res);
    }
    if (unlikely(res))
    memset(to + (n - res), 0, res);
    --
    2.37.0.rc0.161.g10f37bed90-goog
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