linux-kernel - Re: [PATCH 4/9] selinux: enclose macro arguments in parenthesis

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Message-ID: <CAKwvOdmLAhbvvqi7900yAS5zV8c_Hb7a-Tj_NyVHxh+mePpQbQ@mail.gmail.com>
Date:   Tue, 25 Jan 2022 12:40:19 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Christian Göttsche <cgzones@...glemail.com>
Cc:     selinux@...r.kernel.org, Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Xiong Zhenwu <xiong.zhenwu@....com.cn>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Xiu Jianfeng <xiujianfeng@...wei.com>,
        Jeff Vander Stoep <jeffv@...gle.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH 4/9] selinux: enclose macro arguments in parenthesis

On Tue, Jan 25, 2022 at 6:14 AM Christian Göttsche
<cgzones@...glemail.com> wrote:
>
> Enclose the macro arguments in parenthesis to avoid potential evaluation
> order issues.
>
> Note the xperm and ebitmap macros are still not side-effect safe due to
> double evaluation.
>
> Reported by clang-tidy [bugprone-macro-parentheses]

Good idea to run clang-tidy :)
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
> ---
>  security/selinux/include/security.h | 4 ++--
>  security/selinux/ss/ebitmap.h       | 6 +++---
>  security/selinux/ss/sidtab.c        | 4 ++--
>  3 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index 6482e0efb368..d91a5672de99 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -254,8 +254,8 @@ struct av_decision {
>  #define XPERMS_AUDITALLOW 2
>  #define XPERMS_DONTAUDIT 4
>
> -#define security_xperm_set(perms, x) (perms[x >> 5] |= 1 << (x & 0x1f))
> -#define security_xperm_test(perms, x) (1 & (perms[x >> 5] >> (x & 0x1f)))
> +#define security_xperm_set(perms, x) ((perms)[(x) >> 5] |= 1 << ((x) & 0x1f))
> +#define security_xperm_test(perms, x) (1 & ((perms)[(x) >> 5] >> ((x) & 0x1f)))
>  struct extended_perms_data {
>         u32 p[8];
>  };
> diff --git a/security/selinux/ss/ebitmap.h b/security/selinux/ss/ebitmap.h
> index 9eb2d0af2805..58eb822f11ee 100644
> --- a/security/selinux/ss/ebitmap.h
> +++ b/security/selinux/ss/ebitmap.h
> @@ -118,9 +118,9 @@ static inline void ebitmap_node_clr_bit(struct ebitmap_node *n,
>  }
>
>  #define ebitmap_for_each_positive_bit(e, n, bit)       \
> -       for (bit = ebitmap_start_positive(e, &n);       \
> -            bit < ebitmap_length(e);                   \
> -            bit = ebitmap_next_positive(e, &n, bit))   \
> +       for ((bit) = ebitmap_start_positive(e, &(n));   \
> +            (bit) < ebitmap_length(e);                 \
> +            (bit) = ebitmap_next_positive(e, &(n), bit))       \
>
>  int ebitmap_cmp(struct ebitmap *e1, struct ebitmap *e2);
>  int ebitmap_cpy(struct ebitmap *dst, struct ebitmap *src);
> diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
> index 293ec048af08..a54b8652bfb5 100644
> --- a/security/selinux/ss/sidtab.c
> +++ b/security/selinux/ss/sidtab.c
> @@ -27,8 +27,8 @@ struct sidtab_str_cache {
>         char str[];
>  };
>
> -#define index_to_sid(index) (index + SECINITSID_NUM + 1)
> -#define sid_to_index(sid) (sid - (SECINITSID_NUM + 1))
> +#define index_to_sid(index) ((index) + SECINITSID_NUM + 1)
> +#define sid_to_index(sid) ((sid) - (SECINITSID_NUM + 1))
>
>  int sidtab_init(struct sidtab *s)
>  {
> --
> 2.34.1
>


-- 
Thanks,
~Nick Desaulniers