Re: [PATCH] target: core: fix invalid memory access

[Mike Christie <michael.christie@oracle.com>]

On 4/7/23 8:00 AM, Maurizio Lombardi wrote:
> nr_attrs should start counting from zero, otherwise we
> will end up dereferencing an invalid memory address.
> 
> $ targetcli /loopback create
> 
>  general protection fault
>  RIP: 0010:configfs_create_file+0x12/0x70
>  Call Trace:
>   <TASK>
>   configfs_attach_item.part.0+0x5f/0x150
>   configfs_attach_group.isra.0+0x49/0x120
>   configfs_mkdir+0x24f/0x4d0
>   vfs_mkdir+0x192/0x240
>   do_mkdirat+0x131/0x160
>   __x64_sys_mkdir+0x48/0x70
>   do_syscall_64+0x5c/0x90
> 
> Fixes: 31177b74790c ("scsi: target: core: Add RTPI attribute for target port")
> 
> Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
> ---
>  drivers/target/target_core_fabric_configfs.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/target/target_core_fabric_configfs.c b/drivers/target/target_core_fabric_configfs.c
> index 0ce47e21e0c8..b7c637644cd4 100644
> --- a/drivers/target/target_core_fabric_configfs.c
> +++ b/drivers/target/target_core_fabric_configfs.c
> @@ -885,7 +885,7 @@ target_fabric_setup_tpg_base_cit(struct target_fabric_configfs *tf)
>  {
>  	struct config_item_type *cit = &tf->tf_tpg_base_cit;
>  	struct configfs_attribute **attrs = NULL;
> -	size_t nr_attrs = 1;
> +	size_t nr_attrs = 0;
>  	int i = 0;
>  
>  	if (tf->tf_ops->tfc_tpg_base_attrs)
> @@ -895,8 +895,8 @@ target_fabric_setup_tpg_base_cit(struct target_fabric_configfs *tf)
>  	if (tf->tf_ops->fabric_enable_tpg)
>  		nr_attrs++;
>  
> -	if (nr_attrs == 0)
> -		goto done;
> +	/* + 1 for target_fabric_tpg_base_attr_rtpi */
> +	nr_attrs++;
>  
>  	/* + 1 for final NULL in the array */
>  	attrs = kcalloc(nr_attrs + 1, sizeof(*attrs), GFP_KERNEL);
> @@ -912,7 +912,6 @@ target_fabric_setup_tpg_base_cit(struct target_fabric_configfs *tf)
>  
>  	attrs[i++] = &target_fabric_tpg_base_attr_rtpi;
>  
> -done:
>  	cit->ct_item_ops = &target_fabric_tpg_base_item_ops;
>  	cit->ct_attrs = attrs;
>  	cit->ct_owner = tf->tf_ops->module;

Reviewed-by: Mike Christie <michael.christie@oracle.com>