linux-kernel - [PATCH] capability: erase checker warnings about struct __user_cap_data

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Date:   Fri,  2 Jun 2023 13:45:27 +0800
From:   "GONG, Ruiqi" <gongruiqi@...weicloud.com>
To:     Serge Hallyn <serge@...lyn.com>
Cc:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Wang Weiyang <wangweiyang2@...wei.com>,
        Xiu Jianfeng <xiujianfeng@...wei.com>, gongruiqi1@...wei.com
Subject: [PATCH] capability: erase checker warnings about struct __user_cap_data_struct

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@...weicloud.com>
---
 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