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    Subject[PATCH 08/45] arm64: uaccess: consistently check object sizes
    Date
    From: Mark Rutland <mark.rutland@arm.com>

    commit 76624175dca upstream.

    Currently in arm64's copy_{to,from}_user, we only check the
    source/destination object size if access_ok() tells us the user access
    is permissible.

    However, in copy_from_user() we'll subsequently zero any remainder on
    the destination object. If we failed the access_ok() check, that applies
    to the whole object size, which we didn't check.

    To ensure that we catch that case, this patch hoists check_object_size()
    to the start of copy_from_user(), matching __copy_from_user() and
    __copy_to_user(). To make all of our uaccess copy primitives consistent,
    the same is done to copy_to_user().

    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Acked-by: Kees Cook <keescook@chromium.org>
    Signed-off-by: Mark Rutland <mark.rutland@arm.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Alex Shi <alex.shi@linaro.org>
    ---
    arch/arm64/include/asm/uaccess.h | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
    index 94e1457..09c9b59 100644
    --- a/arch/arm64/include/asm/uaccess.h
    +++ b/arch/arm64/include/asm/uaccess.h
    @@ -326,9 +326,9 @@ static inline unsigned long __must_check copy_from_user(void *to, const void __u
    {
    unsigned long res = n;
    kasan_check_write(to, n);
    + check_object_size(to, n, false);

    if (access_ok(VERIFY_READ, from, n)) {
    - check_object_size(to, n, false);
    res = __arch_copy_from_user(to, from, n);
    }
    if (unlikely(res))
    @@ -339,9 +339,9 @@ static inline unsigned long __must_check copy_from_user(void *to, const void __u
    static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
    {
    kasan_check_read(from, n);
    + check_object_size(from, n, true);

    if (access_ok(VERIFY_WRITE, to, n)) {
    - check_object_size(from, n, true);
    n = __arch_copy_to_user(to, from, n);
    }
    return n;
    --
    2.7.4
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