slab: add struct kmem_cache_args

Currently we have multiple kmem_cache_create*() variants that take up to
seven separate parameters with one of the functions having to grow an
eigth parameter in the future to handle both usercopy and a custom
freelist pointer.

Add a struct kmem_cache_args structure and move less common parameters
into it. Core parameters such as name, object size, and flags continue
to be passed separately.

Add a new function __kmem_cache_create_args() that takes a struct
kmem_cache_args pointer and port do_kmem_cache_create_usercopy() over to
it.

In follow-up patches we will port the other kmem_cache_create*()
variants over to it as well.

Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 5b2da2cf31a8b185c6508fed91c9c6bba0e07987..2b8eeca7fd2cbd0a5932660527270946aee3688d 100644 (file)
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -240,6 +240,28 @@ struct mem_cgroup;
  */
 bool slab_is_available(void);
 
+/**
+ * struct kmem_cache_args - Less common arguments for kmem_cache_create()
+ * @align: The required alignment for the objects.
+ * @useroffset: Usercopy region offset
+ * @usersize: Usercopy region size
+ * @freeptr_offset: Custom offset for the free pointer in RCU caches
+ * @use_freeptr_offset: Whether a @freeptr_offset is used
+ * @ctor: A constructor for the objects.
+ */
+struct kmem_cache_args {
+       unsigned int align;
+       unsigned int useroffset;
+       unsigned int usersize;
+       unsigned int freeptr_offset;
+       bool use_freeptr_offset;
+       void (*ctor)(void *);
+};
+
+struct kmem_cache *__kmem_cache_create_args(const char *name,
+                                           unsigned int object_size,
+                                           struct kmem_cache_args *args,
+                                           slab_flags_t flags);
 struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,
                        unsigned int align, slab_flags_t flags,
                        void (*ctor)(void *));

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 91e0e36e437946b1a6f4770eb5dbaa293e45e706..0f13c045b8d1d0b2b5528785de6f4aebacbcb0ba 100644 (file)
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -248,14 +248,24 @@ out:
        return ERR_PTR(err);
 }
 
-static struct kmem_cache *
-do_kmem_cache_create_usercopy(const char *name,
-                 unsigned int size, unsigned int freeptr_offset,
-                 unsigned int align, slab_flags_t flags,
-                 unsigned int useroffset, unsigned int usersize,
-                 void (*ctor)(void *))
+/**
+ * __kmem_cache_create_args - Create a kmem cache
+ * @name: A string which is used in /proc/slabinfo to identify this cache.
+ * @object_size: The size of objects to be created in this cache.
+ * @args: Arguments for the cache creation (see struct kmem_cache_args).
+ * @flags: See %SLAB_* flags for an explanation of individual @flags.
+ *
+ * Cannot be called within a interrupt, but can be interrupted.
+ *
+ * Return: a pointer to the cache on success, NULL on failure.
+ */
+struct kmem_cache *__kmem_cache_create_args(const char *name,
+                                           unsigned int object_size,
+                                           struct kmem_cache_args *args,
+                                           slab_flags_t flags)
 {
        struct kmem_cache *s = NULL;
+       unsigned int freeptr_offset = UINT_MAX;
        const char *cache_name;
        int err;
 
@@ -275,7 +285,7 @@ do_kmem_cache_create_usercopy(const char *name,
 
        mutex_lock(&slab_mutex);
 
-       err = kmem_cache_sanity_check(name, size);
+       err = kmem_cache_sanity_check(name, object_size);
        if (err) {
                goto out_unlock;
        }
@@ -296,12 +306,14 @@ do_kmem_cache_create_usercopy(const char *name,
 
        /* Fail closed on bad usersize of useroffset values. */
        if (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) ||
-           WARN_ON(!usersize && useroffset) ||
-           WARN_ON(size < usersize || size - usersize < useroffset))
-               usersize = useroffset = 0;
-
-       if (!usersize)
-               s = __kmem_cache_alias(name, size, align, flags, ctor);
+           WARN_ON(!args->usersize && args->useroffset) ||
+           WARN_ON(object_size < args->usersize ||
+                   object_size - args->usersize < args->useroffset))
+               args->usersize = args->useroffset = 0;
+
+       if (!args->usersize)
+               s = __kmem_cache_alias(name, object_size, args->align, flags,
+                                      args->ctor);
        if (s)
                goto out_unlock;
 
@@ -311,9 +323,11 @@ do_kmem_cache_create_usercopy(const char *name,
                goto out_unlock;
        }
 
-       s = create_cache(cache_name, size, freeptr_offset,
-                        calculate_alignment(flags, align, size),
-                        flags, useroffset, usersize, ctor);
+       if (args->use_freeptr_offset)
+               freeptr_offset = args->freeptr_offset;
+       s = create_cache(cache_name, object_size, freeptr_offset,
+                        calculate_alignment(flags, args->align, object_size),
+                        flags, args->useroffset, args->usersize, args->ctor);
        if (IS_ERR(s)) {
                err = PTR_ERR(s);
                kfree_const(cache_name);
@@ -335,6 +349,27 @@ out_unlock:
        }
        return s;
 }
+EXPORT_SYMBOL(__kmem_cache_create_args);
+
+static struct kmem_cache *
+do_kmem_cache_create_usercopy(const char *name,
+                 unsigned int size, unsigned int freeptr_offset,
+                 unsigned int align, slab_flags_t flags,
+                 unsigned int useroffset, unsigned int usersize,
+                 void (*ctor)(void *))
+{
+       struct kmem_cache_args kmem_args = {
+               .align                  = align,
+               .use_freeptr_offset     = freeptr_offset != UINT_MAX,
+               .freeptr_offset         = freeptr_offset,
+               .useroffset             = useroffset,
+               .usersize               = usersize,
+               .ctor                   = ctor,
+       };
+
+       return __kmem_cache_create_args(name, size, &kmem_args, flags);
+}
+
 
 /**
  * kmem_cache_create_usercopy - Create a cache with a region suitable