On Wed, Mar 27, 2024 at 7:26 PM Ayush Tiwari <ayushtiw0110@xxxxxxxxx> wrote:
>
> Use kmem_cache replace kzalloc() calls with kmem_cache_zalloc() for
> struct landlock_object and update the related dependencies.
>
> Signed-off-by: Ayush Tiwari <ayushtiw0110@xxxxxxxxx>
> ---
> security/landlock/fs.c | 2 +-
> security/landlock/object.c | 14 ++++++++++++--
> security/landlock/object.h | 4 ++++
> security/landlock/setup.c | 2 ++
> 4 files changed, 19 insertions(+), 3 deletions(-)
Hi Ayush,
Mickaël has the final say on Landlock patches, but I had a few
comments that I've included below ...
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index fc520a06f9af..227dd67dd902 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -124,7 +124,7 @@ static struct landlock_object *get_inode_object(struct inode *const inode)
> if (unlikely(rcu_access_pointer(inode_sec->object))) {
> /* Someone else just created the object, bail out and retry. */
> spin_unlock(&inode->i_lock);
> - kfree(new_object);
> + kmem_cache_free(landlock_object_cache, new_object);
See my comment below, but you may want to wrap this in a Landlock
object API function.
> rcu_read_lock();
> goto retry;
> diff --git a/security/landlock/object.c b/security/landlock/object.c
> index 1f50612f0185..df1354215617 100644
> --- a/security/landlock/object.c
> +++ b/security/landlock/object.c
> @@ -17,6 +17,15 @@
>
> #include "object.h"
>
> +struct kmem_cache *landlock_object_cache;
> +
> +void __init landlock_object_init(void)
> +{
> + landlock_object_cache = kmem_cache_create(
> + "landlock_object_cache", sizeof(struct landlock_object), 0,
> + SLAB_PANIC, NULL);
The comments in include/linux/slab.h suggest using the KMEM_CACHE()
macro, instead of kmem_cache_create(), as a best practice for creating
slab caches.
> +}
> +
> struct landlock_object *
> landlock_create_object(const struct landlock_object_underops *const underops,
> void *const underobj)
> @@ -25,7 +34,8 @@ landlock_create_object(const struct landlock_object_underops *const underops,
>
> if (WARN_ON_ONCE(!underops || !underobj))
> return ERR_PTR(-ENOENT);
> - new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT);
> + new_object =
> + kmem_cache_zalloc(landlock_object_cache, GFP_KERNEL_ACCOUNT);
If the line is too long, you might want to consider splitting the
function parameters like this:
new_object = kmem_cache_zalloc(landlock_object_cache,
GFP_KERNEL_ACCOUNT);
> if (!new_object)
> return ERR_PTR(-ENOMEM);
> refcount_set(&new_object->usage, 1);
> @@ -62,6 +72,6 @@ void landlock_put_object(struct landlock_object *const object)
> * @object->underobj to @object (if it still exists).
> */
> object->underops->release(object);
> - kfree_rcu(object, rcu_free);
> + kmem_cache_free(landlock_object_cache, object);
> }
> }
> diff --git a/security/landlock/object.h b/security/landlock/object.h
> index 5f28c35e8aa8..8ba1af3ddc2e 100644
> --- a/security/landlock/object.h
> +++ b/security/landlock/object.h
> @@ -13,6 +13,10 @@
> #include <linux/refcount.h>
> #include <linux/spinlock.h>
>
> +extern struct kmem_cache *landlock_object_cache;
This really is a decision for Mickaël, but you may want to make
@landlock_object_cache private to object.c and create functions to
manage it as needed, e.g. put/free operations.
> +void __init landlock_object_init(void);
> +
> struct landlock_object;
>
> /**
> diff --git a/security/landlock/setup.c b/security/landlock/setup.c
> index f6dd33143b7f..a5fca4582ee1 100644
--
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