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From:   Bartosz Golaszewski <brgl@bgdev.pl>
Date:   Thu, 25 Jul 2019 09:08:32 +0200
Message-ID: <CAMRc=MeZOgY=qHNZf635i1OOnrx6Rh2D1qTSBPQjk_CGrRo-Tg@mail.gmail.com>
Subject: Re: [PATCH] modules: always page-align module section allocations
To:     Jessica Yu <jeyu@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Yang Yingliang <yangyingliang@huawei.com>,
        Jian Cheng <cj.chengjian@huawei.com>,
        Nadav Amit <namit@vmware.com>, Sekhar Nori <nsekhar@ti.com>,
        Kevin Hilman <khilman@kernel.org>,
        David Lechner <david@lechnology.com>,
        Adam Ford <aford173@gmail.com>, Martin Kaiser <lists@kaiser.cx>
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=C5=9Br., 24 lip 2019 o 17:02 Jessica Yu <jeyu@kernel.org> napisa=C5=82(a):
>
> Some arches (e.g., arm64, x86) have moved towards non-executable
> module_alloc() allocations for security hardening reasons. That means
> that the module loader will need to set the text section of a module to
> executable, regardless of whether or not CONFIG_STRICT_MODULE_RWX is set.
>
> When CONFIG_STRICT_MODULE_RWX=3Dy, module section allocations are always
> page-aligned to handle memory rwx permissions. On some arches with
> CONFIG_STRICT_MODULE_RWX=3Dn however, when setting the module text to
> executable, the BUG_ON() in frob_text() gets triggered since module
> section allocations are not page-aligned when CONFIG_STRICT_MODULE_RWX=3D=
n.
> Since the set_memory_* API works with pages, and since we need to call
> set_memory_x() regardless of whether CONFIG_STRICT_MODULE_RWX is set, we
> might as well page-align all module section allocations for ease of
> managing rwx permissions of module sections (text, rodata, etc).
>
> Fixes: 2eef1399a866 ("modules: fix BUG when load module with rodata=3Dn")
> Reported-by: Martin Kaiser <lists@kaiser.cx>
> Reported-by: Bartosz Golaszewski <brgl@bgdev.pl>
> Tested-by: David Lechner <david@lechnology.com>
> Tested-by: Martin Kaiser <martin@kaiser.cx>
> Signed-off-by: Jessica Yu <jeyu@kernel.org>
> ---
>  kernel/module.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 5933395af9a0..cd8df516666d 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -64,14 +64,9 @@
>
>  /*
>   * Modules' sections will be aligned on page boundaries
> - * to ensure complete separation of code and data, but
> - * only when CONFIG_STRICT_MODULE_RWX=3Dy
> + * to ensure complete separation of code and data
>   */
> -#ifdef CONFIG_STRICT_MODULE_RWX
>  # define debug_align(X) ALIGN(X, PAGE_SIZE)
> -#else
> -# define debug_align(X) (X)
> -#endif
>
>  /* If this is set, the section belongs in the init part of the module */
>  #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
> --
> 2.16.4
>

Tested-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>