pid: use struct_size_t() helper

Before commit d67790ddf021 ("overflow: Add struct_size_t() helper") only
struct_size() existed, which expects a valid pointer instance containing
the flexible array.

However, when we determine the default struct pid allocation size for
the associated kmem cache of a pid namespace we need to take the nesting
depth of the pid namespace into account without an variable instance
necessarily being available.

In commit b69f0aeb0689 ("pid: Replace struct pid 1-element array with
flex-array") we used to handle this the old fashioned way and cast NULL
to a struct pid pointer type. However, we do apparently have a dedicated
struct_size_t() helper for exactly this case. So switch to that.

Suggested-by: Kees Cook <keescook@chromium.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/pid.c b/kernel/pid.c
index 8bce3ae..6a1d23a 100644 (file)
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -657,7 +657,7 @@ void __init pid_idr_init(void)
        idr_init(&init_pid_ns.idr);
 
        init_pid_ns.pid_cachep = kmem_cache_create("pid",
-                       struct_size((struct pid *)NULL, numbers, 1),
+                       struct_size_t(struct pid, numbers, 1),
                        __alignof__(struct pid),
                        SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT,
                        NULL);

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 70a9297..0bf44af 100644 (file)
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -48,7 +48,7 @@ static struct kmem_cache *create_pid_cachep(unsigned int level)
                return kc;
 
        snprintf(name, sizeof(name), "pid_%u", level + 1);
-       len = struct_size((struct pid *)NULL, numbers, level + 1);
+       len = struct_size_t(struct pid, numbers, level + 1);
        mutex_lock(&pid_caches_mutex);
        /* Name collision forces to do allocation under mutex. */
        if (!*pkc)