Re: [PATCH] modules: always page-align module section allocations

[Bartosz Golaszewski]

År., 24 lip 2019 o 17:02 Jessica Yu <jeyu@xxxxxxxxxx> napisaÅ(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=y, module section allocations are always
> page-aligned to handle memory rwx permissions. On some arches with
> CONFIG_STRICT_MODULE_RWX=n 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=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=n")
> Reported-by: Martin Kaiser <lists@xxxxxxxxx>
> Reported-by: Bartosz Golaszewski <brgl@xxxxxxxx>
> Tested-by: David Lechner <david@xxxxxxxxxxxxxx>
> Tested-by: Martin Kaiser <martin@xxxxxxxxx>
> Signed-off-by: Jessica Yu <jeyu@xxxxxxxxxx>
> ---
>  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=y
> + * 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@xxxxxxxxxxxx>