Hi Mickaël,
On 21/2/22 16:53, Mickaël Salaün wrote:
From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>
Replace the enum landlock_rule_type with an int in the syscall signature
of landlock_add_rule to avoid an implementation-defined size. In
practice an enum type is like an int (at least with GCC and clang), but
compilers may accept options (e.g. -fshort-enums) that would have an
impact on that [1]. This change is mostly a cosmetic fix according to
the current kernel compilers and used options.
There are two proposals for C2x that might bring C++ syntax to C for
enums, i.e., being able to specify the underlying type of an enum.
See:
<http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2904.htm>
<http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2908.htm>
Since the current kernel is safe from that enum problem, it may be
better to wait and see what the standard decides to do with enum. I
guess they'll add this feature sooner or later.
Regards,
Alex
Link: https://lore.kernel.org/r/8a22a3c2-468c-e96c-6516-22a0f029aa34@xxxxxxxxx/ [1]
Reported-by: Alejandro Colomar <alx.manpages@xxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220221155311.166278-3-mic@xxxxxxxxxxx
---
include/linux/syscalls.h | 3 +--
security/landlock/syscalls.c | 7 ++++---
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 819c0cb00b6d..a5956f91caf2 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -71,7 +71,6 @@ struct clone_args;
struct open_how;
struct mount_attr;
struct landlock_ruleset_attr;
-enum landlock_rule_type;
#include <linux/types.h>
#include <linux/aio_abi.h>
@@ -1053,7 +1052,7 @@ asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
asmlinkage long sys_pidfd_getfd(int pidfd, int fd, unsigned int flags);
asmlinkage long sys_landlock_create_ruleset(const struct landlock_ruleset_attr __user *attr,
size_t size, __u32 flags);
-asmlinkage long sys_landlock_add_rule(int ruleset_fd, enum landlock_rule_type rule_type,
+asmlinkage long sys_landlock_add_rule(int ruleset_fd, int rule_type,
const void __user *rule_attr, __u32 flags);
asmlinkage long sys_landlock_restrict_self(int ruleset_fd, __u32 flags);
asmlinkage long sys_memfd_secret(unsigned int flags);
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index fd4b24022a06..3b40fc5d0216 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -277,8 +277,9 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
*
* @ruleset_fd: File descriptor tied to the ruleset that should be extended
* with the new rule.
- * @rule_type: Identify the structure type pointed to by @rule_attr (only
- * LANDLOCK_RULE_PATH_BENEATH for now).
+ * @rule_type: Identify the structure type pointed to by @rule_attr as defined
+ * by enum landlock_rule_type (only LANDLOCK_RULE_PATH_BENEATH for
+ * now).
* @rule_attr: Pointer to a rule (only of type &struct
* landlock_path_beneath_attr for now).
* @flags: Must be 0.
@@ -301,7 +302,7 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
* - EFAULT: @rule_attr inconsistency.
*/
SYSCALL_DEFINE4(landlock_add_rule,
- const int, ruleset_fd, const enum landlock_rule_type, rule_type,
+ const int, ruleset_fd, const int, rule_type,
const void __user *const, rule_attr, const __u32, flags)
{
struct landlock_path_beneath_attr path_beneath_attr;
