* [PATCH] landlock: Drop "const" argument qualifier to avoid GCC 4.9 warnings
@ 2021-09-10 22:36 Kees Cook
2021-09-13 11:19 ` Mickaël Salaün
0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2021-09-10 22:36 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Kees Cook, James Morris, Serge E. Hallyn, linux-security-module,
linux-kernel, linux-hardening
When building under GCC 4.9, the compiler warns about const mismatches:
security/landlock/ruleset.c: In function 'insert_rule':
security/landlock/ruleset.c:196:34: error: passing argument 2 of 'create_rule' from incompatible pointer type [-Werror]
new_rule = create_rule(object, &this->layers, this->num_layers,
^
security/landlock/ruleset.c:69:30: note: expected 'const struct landlock_layer ** const' but argument is of type 'struct landlock_layer (*)[]'
static struct landlock_rule *create_rule(
^
security/landlock/ruleset.c: In function 'landlock_insert_rule':
security/landlock/ruleset.c:240:38: error: passing argument 3 of 'insert_rule' from incompatible pointer type [-Werror]
return insert_rule(ruleset, object, &layers, ARRAY_SIZE(layers));
^
security/landlock/ruleset.c:144:12: note: expected 'const struct landlock_layer ** const' but argument is of type 'struct landlock_layer (*)[1]'
static int insert_rule(struct landlock_ruleset *const ruleset,
^
Drop "const" from the function definition.
Cc: "Mickaël Salaün" <mic@digikod.net>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
security/landlock/ruleset.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index ec72b9262bf3..64c37af88ee7 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -68,7 +68,7 @@ static void build_check_rule(void)
static struct landlock_rule *create_rule(
struct landlock_object *const object,
- const struct landlock_layer (*const layers)[],
+ struct landlock_layer (*layers)[],
const u32 num_layers,
const struct landlock_layer *const new_layer)
{
@@ -143,7 +143,7 @@ static void build_check_ruleset(void)
*/
static int insert_rule(struct landlock_ruleset *const ruleset,
struct landlock_object *const object,
- const struct landlock_layer (*const layers)[],
+ struct landlock_layer (*layers)[],
size_t num_layers)
{
struct rb_node **walker_node;
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] landlock: Drop "const" argument qualifier to avoid GCC 4.9 warnings
2021-09-10 22:36 [PATCH] landlock: Drop "const" argument qualifier to avoid GCC 4.9 warnings Kees Cook
@ 2021-09-13 11:19 ` Mickaël Salaün
2021-09-13 16:16 ` Kees Cook
0 siblings, 1 reply; 3+ messages in thread
From: Mickaël Salaün @ 2021-09-13 11:19 UTC (permalink / raw)
To: Kees Cook
Cc: James Morris, Serge E. Hallyn, linux-security-module,
linux-kernel, linux-hardening
On 11/09/2021 00:36, Kees Cook wrote:
> When building under GCC 4.9, the compiler warns about const mismatches:
>
> security/landlock/ruleset.c: In function 'insert_rule':
> security/landlock/ruleset.c:196:34: error: passing argument 2 of 'create_rule' from incompatible pointer type [-Werror]
> new_rule = create_rule(object, &this->layers, this->num_layers,
> ^
> security/landlock/ruleset.c:69:30: note: expected 'const struct landlock_layer ** const' but argument is of type 'struct landlock_layer (*)[]'
> static struct landlock_rule *create_rule(
> ^
> security/landlock/ruleset.c: In function 'landlock_insert_rule':
> security/landlock/ruleset.c:240:38: error: passing argument 3 of 'insert_rule' from incompatible pointer type [-Werror]
> return insert_rule(ruleset, object, &layers, ARRAY_SIZE(layers));
> ^
> security/landlock/ruleset.c:144:12: note: expected 'const struct landlock_layer ** const' but argument is of type 'struct landlock_layer (*)[1]'
> static int insert_rule(struct landlock_ruleset *const ruleset,
I guess this is a bug in GCC 4.9 (i.e. missing automatic const upgrade).
Couldn't we backport a fix to GCC 4.9 instead?
> ^
>
> Drop "const" from the function definition.
>
> Cc: "Mickaël Salaün" <mic@digikod.net>
> Cc: James Morris <jmorris@namei.org>
> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> Cc: linux-security-module@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> security/landlock/ruleset.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
> index ec72b9262bf3..64c37af88ee7 100644
> --- a/security/landlock/ruleset.c
> +++ b/security/landlock/ruleset.c
> @@ -68,7 +68,7 @@ static void build_check_rule(void)
>
> static struct landlock_rule *create_rule(
> struct landlock_object *const object,
> - const struct landlock_layer (*const layers)[],
> + struct landlock_layer (*layers)[],
The "const layers" is not an issue, it should not be removed.
> const u32 num_layers,
> const struct landlock_layer *const new_layer)
> {
> @@ -143,7 +143,7 @@ static void build_check_ruleset(void)
> */
> static int insert_rule(struct landlock_ruleset *const ruleset,
> struct landlock_object *const object,
> - const struct landlock_layer (*const layers)[],
> + struct landlock_layer (*layers)[],
Same here for the second const.
> size_t num_layers)
> {
> struct rb_node **walker_node;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] landlock: Drop "const" argument qualifier to avoid GCC 4.9 warnings
2021-09-13 11:19 ` Mickaël Salaün
@ 2021-09-13 16:16 ` Kees Cook
0 siblings, 0 replies; 3+ messages in thread
From: Kees Cook @ 2021-09-13 16:16 UTC (permalink / raw)
To: Mickaël Salaün
Cc: James Morris, Serge E. Hallyn, linux-security-module,
linux-kernel, linux-hardening
On Mon, Sep 13, 2021 at 01:19:19PM +0200, Mickaël Salaün wrote:
>
> On 11/09/2021 00:36, Kees Cook wrote:
> > When building under GCC 4.9, the compiler warns about const mismatches:
> >
> > security/landlock/ruleset.c: In function 'insert_rule':
> > security/landlock/ruleset.c:196:34: error: passing argument 2 of 'create_rule' from incompatible pointer type [-Werror]
> > new_rule = create_rule(object, &this->layers, this->num_layers,
> > ^
> > security/landlock/ruleset.c:69:30: note: expected 'const struct landlock_layer ** const' but argument is of type 'struct landlock_layer (*)[]'
> > static struct landlock_rule *create_rule(
> > ^
> > security/landlock/ruleset.c: In function 'landlock_insert_rule':
> > security/landlock/ruleset.c:240:38: error: passing argument 3 of 'insert_rule' from incompatible pointer type [-Werror]
> > return insert_rule(ruleset, object, &layers, ARRAY_SIZE(layers));
> > ^
> > security/landlock/ruleset.c:144:12: note: expected 'const struct landlock_layer ** const' but argument is of type 'struct landlock_layer (*)[1]'
> > static int insert_rule(struct landlock_ruleset *const ruleset,
>
> I guess this is a bug in GCC 4.9 (i.e. missing automatic const upgrade).
> Couldn't we backport a fix to GCC 4.9 instead?
I don't disagree, but I'm just trying to deal with the fall-out of
-Werror. Perhaps speak up on this thread in support of deprecating
GCC 4.9?
https://lore.kernel.org/lkml/20210910234047.1019925-1-ndesaulniers@google.com/
-Kees
--
Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-09-10 22:36 [PATCH] landlock: Drop "const" argument qualifier to avoid GCC 4.9 warnings Kees Cook
2021-09-13 11:19 ` Mickaël Salaün
2021-09-13 16:16 ` Kees Cook
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