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Message-ID: <20190410191120.GA109588@google.com>
Date: Wed, 10 Apr 2019 15:11:20 -0400
From: Joel Fernandes <joel@...lfernandes.org>
To: linux-kernel@...r.kernel.org
Cc: paulmck@...ux.vnet.ibm.com, rostedt@...dmis.org,
mathieu.desnoyers@...icios.com, rcu@...r.kernel.org,
kernel-hardening@...ts.openwall.com, kernel-team@...roid.com,
keescook@...omium.org, Jessica Yu <jeyu@...nel.org>
Subject: Re: [PATCH v2 1/3] module: Prepare for addition of new ro_after_init
sections
On Wed, Apr 10, 2019 at 03:08:21PM -0400, Joel Fernandes (Google) wrote:
> For the purposes of hardening modules by adding sections to
> ro_after_init sections, prepare for addition of new ro_after_init
> entries which we do in future patches. Create a table to which new
> entries could be added later. This makes it less error prone and reduce
> code duplication.
>
> Cc: paulmck@...ux.vnet.ibm.com
> Cc: rostedt@...dmis.org
> Cc: mathieu.desnoyers@...icios.com
> Cc: rcu@...r.kernel.org
> Cc: kernel-hardening@...ts.openwall.com
> Cc: kernel-team@...roid.com
> Suggested-by: keescook@...omium.org
> Reviewed-by: keescook@...omium.org
> Acked-by: rostedt@...dmis.org
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
>
> ---
> kernel/module.c | 41 +++++++++++++++++++++++------------------
> 1 file changed, 23 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 524da609c884..1acddb93282a 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3300,11 +3300,27 @@ static bool blacklisted(const char *module_name)
> }
> core_param(module_blacklist, module_blacklist, charp, 0400);
>
> +/*
> + * Mark ro_after_init section with SHF_RO_AFTER_INIT so that
> + * layout_sections() can put it in the right place.
> + * Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set.
> + */
> +static char *ro_after_init_sections[] = {
> + ".data..ro_after_init",
> +
> + /*
> + * __jump_table structures are never modified, with the exception of
> + * entries that refer to code in the __init section, which are
> + * annotated as such at module load time.
> + */
> + "__jump_table",
> +};
> +
> static struct module *layout_and_allocate(struct load_info *info, int flags)
> {
> struct module *mod;
> unsigned int ndx;
> - int err;
> + int err, i;
>
> err = check_modinfo(info->mod, info, flags);
> if (err)
> @@ -3319,23 +3335,12 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
> /* We will do a special allocation for per-cpu sections later. */
> info->sechdrs[info->index.pcpu].sh_flags &= ~(unsigned long)SHF_ALLOC;
>
> - /*
> - * Mark ro_after_init section with SHF_RO_AFTER_INIT so that
> - * layout_sections() can put it in the right place.
> - * Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set.
> - */
> - ndx = find_sec(info, ".data..ro_after_init");
> - if (ndx)
> - info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;
> - /*
> - * Mark the __jump_table section as ro_after_init as well: these data
> - * structures are never modified, with the exception of entries that
> - * refer to code in the __init section, which are annotated as such
> - * at module load time.
> - */
> - ndx = find_sec(info, "__jump_table");
> - if (ndx)
> - info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;
> + /* Set sh_flags for read-only after init sections */
> + for (i = 0; ro_after_init_sections[i]; i++) {
Seems the fixup for this based on Kees suggestion of using NULL got squashed
into 2/3, so allow me to send a v3 to fix this ;-) Sorry! I am doing that
now.
The patches applied together are still code-correct thought.
thanks,
- Joel
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