Re: [PATCH v5 4/8] LSM: lsm_get_self_attr syscall for LSM self attributes

On Thu, Jan 12, 2023 at 9:40 AM Arnd Bergmann [off-list ref] wrote:

On Mon, Jan 9, 2023, at 19:07, Casey Schaufler wrote:

quoted

+/**
+ * struct lsm_ctx - LSM context
+ * @id: the LSM id number, see LSM_ID_XXX
+ * @flags: context specifier and LSM specific flags
+ * @ctx_len: the size of @ctx
+ * @ctx: the LSM context, a nul terminated string
+ *
+ * @ctx in a nul terminated string.
+ *   (strlen(@ctx) < @ctx_len) is always true.
+ *   (strlen(@ctx) == @ctx_len + 1) is not guaranteed.
+ */
+struct lsm_ctx {
+     __u32           id;
+     __u64           flags;
+     __kernel_size_t ctx_len;
+     __u8            ctx[];
+};

I think this should be changed to be the same layout on
all architectures regardless of __u64 alignment and
sizeof(__kernel_size_t) differences, to avoid the need
for compat syscalls and explicit clearing of the
internal padding.

Maybe just use __u64 fields for all three integers?

I have no problem with that ... the ctx[] field is variable length
anyway so keeping it as a __u8 should be fine.

-- 
paul-moore.com