Re: [PATCH] capability: erase checker warnings about struct __user_cap_data_struct

[Serge E. Hallyn]

On Fri, Jun 02, 2023 at 01:45:27PM +0800, GONG, Ruiqi wrote:
> Currently Sparse warns the following when compiling kernel/capability.c:
> 
> kernel/capability.c:191:35: warning: incorrect type in argument 2 (different address spaces)
> kernel/capability.c:191:35:    expected void const *from
> kernel/capability.c:191:35:    got struct __user_cap_data_struct [noderef] __user *
> kernel/capability.c:168:14: warning: dereference of noderef expression
> ...... (multiple noderef warnings on different locations)
> kernel/capability.c:244:29: warning: incorrect type in argument 1 (different address spaces)
> kernel/capability.c:244:29:    expected void *to
> kernel/capability.c:244:29:    got struct __user_cap_data_struct [noderef] __user ( * )[2]
> kernel/capability.c:247:42: warning: dereference of noderef expression
> ...... (multiple noderef warnings on different locations)
> 
> It seems that defining `struct __user_cap_data_struct` together with
> `cap_user_data_t` make Sparse believe that the struct is `noderef` as
> well. Separate their definitions to clarify their respective attributes.
> 
> Signed-off-by: GONG, Ruiqi <gongruiqi@xxxxxxxxxxxxxxx>

Seems ok.

There's still so much noise in the make C=2 output even just for
kernel/capability.c that I'm not sure it's worth it, but no
objection.

Acked-by: Serge Hallyn <serge@xxxxxxxxxx>

> ---
>  include/uapi/linux/capability.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
> index 3d61a0ae055d..5bb906098697 100644
> --- a/include/uapi/linux/capability.h
> +++ b/include/uapi/linux/capability.h
> @@ -41,11 +41,12 @@ typedef struct __user_cap_header_struct {
>  	int pid;
>  } __user *cap_user_header_t;
>  
> -typedef struct __user_cap_data_struct {
> +struct __user_cap_data_struct {
>          __u32 effective;
>          __u32 permitted;
>          __u32 inheritable;
> -} __user *cap_user_data_t;
> +};
> +typedef struct __user_cap_data_struct __user *cap_user_data_t;
>  
>  
>  #define VFS_CAP_REVISION_MASK	0xFF000000
> -- 
> 2.25.1