Re: [RFC PATCH v2 16/34] lsm: cleanup the LSM blob size code

[Casey Schaufler <casey@schaufler-ca.com>]

On 7/21/2025 4:21 PM, Paul Moore wrote:
> Convert the lsm_blob_size fields to unsigned integers as there is no
> current need for them to be negative, change "lsm_set_blob_size()" to
> "lsm_blob_size_update()" to better reflect reality, and perform some
> other minor cleanups to the associated code.
>
> Reviewed-by: Kees Cook <kees@kernel.org>
> Reviewed-by: John Johansen <john.johansen@canonical.com>
> Signed-off-by: Paul Moore <paul@paul-moore.com>

Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>


> ---
>  include/linux/lsm_hooks.h | 28 ++++++++++-----------
>  security/lsm_init.c       | 51 +++++++++++++++++++++++----------------
>  2 files changed, 44 insertions(+), 35 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index bc477fb20d02..a7ecb0791a0f 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -102,20 +102,20 @@ struct security_hook_list {
>   * Security blob size or offset data.
>   */
>  struct lsm_blob_sizes {
> -	int lbs_cred;
> -	int lbs_file;
> -	int lbs_ib;
> -	int lbs_inode;
> -	int lbs_sock;
> -	int lbs_superblock;
> -	int lbs_ipc;
> -	int lbs_key;
> -	int lbs_msg_msg;
> -	int lbs_perf_event;
> -	int lbs_task;
> -	int lbs_xattr_count; /* number of xattr slots in new_xattrs array */
> -	int lbs_tun_dev;
> -	int lbs_bdev;
> +	unsigned int lbs_cred;
> +	unsigned int lbs_file;
> +	unsigned int lbs_ib;
> +	unsigned int lbs_inode;
> +	unsigned int lbs_sock;
> +	unsigned int lbs_superblock;
> +	unsigned int lbs_ipc;
> +	unsigned int lbs_key;
> +	unsigned int lbs_msg_msg;
> +	unsigned int lbs_perf_event;
> +	unsigned int lbs_task;
> +	unsigned int lbs_xattr_count; /* num xattr slots in new_xattrs array */
> +	unsigned int lbs_tun_dev;
> +	unsigned int lbs_bdev;
>  };
>  
>  /*
> diff --git a/security/lsm_init.c b/security/lsm_init.c
> index b1156f414491..aad363e37140 100644
> --- a/security/lsm_init.c
> +++ b/security/lsm_init.c
> @@ -169,16 +169,22 @@ static void __init lsm_order_append(struct lsm_info *lsm, const char *src)
>  		   lsm_is_enabled(lsm) ? "enabled" : "disabled");
>  }
>  
> -static void __init lsm_set_blob_size(int *need, int *lbs)
> +/**
> + * lsm_blob_size_update - Update the LSM blob size and offset information
> + * @sz_req: the requested additional blob size
> + * @sz_cur: the existing blob size
> + */
> +static void __init lsm_blob_size_update(unsigned int *sz_req,
> +					unsigned int *sz_cur)
>  {
> -	int offset;
> +	unsigned int offset;
>  
> -	if (*need <= 0)
> +	if (*sz_req == 0)
>  		return;
>  
> -	offset = ALIGN(*lbs, sizeof(void *));
> -	*lbs = offset + *need;
> -	*need = offset;
> +	offset = ALIGN(*sz_cur, sizeof(void *));
> +	*sz_cur = offset + *sz_req;
> +	*sz_req = offset;
>  }
>  
>  /**
> @@ -193,24 +199,27 @@ static void __init lsm_prepare(struct lsm_info *lsm)
>  		return;
>  
>  	/* Register the LSM blob sizes. */
> -	lsm_set_blob_size(&blobs->lbs_cred, &blob_sizes.lbs_cred);
> -	lsm_set_blob_size(&blobs->lbs_file, &blob_sizes.lbs_file);
> -	lsm_set_blob_size(&blobs->lbs_ib, &blob_sizes.lbs_ib);
> +	blobs = lsm->blobs;
> +	lsm_blob_size_update(&blobs->lbs_cred, &blob_sizes.lbs_cred);
> +	lsm_blob_size_update(&blobs->lbs_file, &blob_sizes.lbs_file);
> +	lsm_blob_size_update(&blobs->lbs_ib, &blob_sizes.lbs_ib);
>  	/* inode blob gets an rcu_head in addition to LSM blobs. */
>  	if (blobs->lbs_inode && blob_sizes.lbs_inode == 0)
>  		blob_sizes.lbs_inode = sizeof(struct rcu_head);
> -	lsm_set_blob_size(&blobs->lbs_inode, &blob_sizes.lbs_inode);
> -	lsm_set_blob_size(&blobs->lbs_ipc, &blob_sizes.lbs_ipc);
> -	lsm_set_blob_size(&blobs->lbs_key, &blob_sizes.lbs_key);
> -	lsm_set_blob_size(&blobs->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
> -	lsm_set_blob_size(&blobs->lbs_perf_event, &blob_sizes.lbs_perf_event);
> -	lsm_set_blob_size(&blobs->lbs_sock, &blob_sizes.lbs_sock);
> -	lsm_set_blob_size(&blobs->lbs_superblock, &blob_sizes.lbs_superblock);
> -	lsm_set_blob_size(&blobs->lbs_task, &blob_sizes.lbs_task);
> -	lsm_set_blob_size(&blobs->lbs_tun_dev, &blob_sizes.lbs_tun_dev);
> -	lsm_set_blob_size(&blobs->lbs_xattr_count,
> -			  &blob_sizes.lbs_xattr_count);
> -	lsm_set_blob_size(&blobs->lbs_bdev, &blob_sizes.lbs_bdev);
> +	lsm_blob_size_update(&blobs->lbs_inode, &blob_sizes.lbs_inode);
> +	lsm_blob_size_update(&blobs->lbs_ipc, &blob_sizes.lbs_ipc);
> +	lsm_blob_size_update(&blobs->lbs_key, &blob_sizes.lbs_key);
> +	lsm_blob_size_update(&blobs->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
> +	lsm_blob_size_update(&blobs->lbs_perf_event,
> +			     &blob_sizes.lbs_perf_event);
> +	lsm_blob_size_update(&blobs->lbs_sock, &blob_sizes.lbs_sock);
> +	lsm_blob_size_update(&blobs->lbs_superblock,
> +			     &blob_sizes.lbs_superblock);
> +	lsm_blob_size_update(&blobs->lbs_task, &blob_sizes.lbs_task);
> +	lsm_blob_size_update(&blobs->lbs_tun_dev, &blob_sizes.lbs_tun_dev);
> +	lsm_blob_size_update(&blobs->lbs_xattr_count,
> +			     &blob_sizes.lbs_xattr_count);
> +	lsm_blob_size_update(&blobs->lbs_bdev, &blob_sizes.lbs_bdev);
>  }
>  
>  /* Initialize a given LSM, if it is enabled. */