[PATCH v2 1/3] module: Prepare for addition of new ro_after_init sections
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: paul...@linux.vnet.ibm.com
Cc: rost...@goodmis.org
Cc: mathieu.desnoy...@efficios.com
Cc: r...@vger.kernel.org
Cc: kernel-harden...@lists.openwall.com
Cc: kernel-t...@android.com
Suggested-by: keesc...@chromium.org
Reviewed-by: keesc...@chromium.org
Acked-by: rost...@goodmis.org
Signed-off-by: Joel Fernandes (Google)
---
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++) {
+ ndx = find_sec(info, ro_after_init_sections[i]);
+ if (ndx)
+ info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;
+ }
/* Determine total sizes, and put offsets in sh_entsize. For now
this is done generically; there doesn't appear to be any
--
2.21.0.392.gf8f6787159e-goog
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: paul...@linux.vnet.ibm.com
> Cc: rost...@goodmis.org
> Cc: mathieu.desnoy...@efficios.com
> Cc: r...@vger.kernel.org
> Cc: kernel-harden...@lists.openwall.com
> Cc: kernel-t...@android.com
> Suggested-by: keesc...@chromium.org
> Reviewed-by: keesc...@chromium.org
> Acked-by: rost...@goodmis.org
> Signed-off-by: Joel Fernandes (Google)
>
> ---
> 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
