lsm: constify the 'file' parameter in security_binder_transfer_file()

SELinux registers the implementation for the "binder_transfer_file"
hook. Looking at the function implementation we observe that the
parameter "file" is not changing.

Mark the "file" parameter of LSM hook security_binder_transfer_file() as
"const" since it will not be changing in the LSM hook.

Signed-off-by: Khadija Kamran <kamrankhadijadj@gmail.com>
[PM: subject line whitespace fix]
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: KhadijaKamran

include/linux/lsm_hook_defs.h

@@ -32,7 +32,7 @@ LSM_HOOK(int, 0, binder_transaction, const struct cred *from,
 LSM_HOOK(int, 0, binder_transfer_binder, const struct cred *from,
 	 const struct cred *to)
 LSM_HOOK(int, 0, binder_transfer_file, const struct cred *from,
-	 const struct cred *to, struct file *file)
+	 const struct cred *to, const struct file *file)
 LSM_HOOK(int, 0, ptrace_access_check, struct task_struct *child,
 	 unsigned int mode)
 LSM_HOOK(int, 0, ptrace_traceme, struct task_struct *parent)

include/linux/security.h

@@ -269,7 +269,7 @@ int security_binder_transaction(const struct cred *from,
 int security_binder_transfer_binder(const struct cred *from,
 				    const struct cred *to);
 int security_binder_transfer_file(const struct cred *from,
-				  const struct cred *to, struct file *file);
+				  const struct cred *to, const struct file *file);
 int security_ptrace_access_check(struct task_struct *child, unsigned int mode);
 int security_ptrace_traceme(struct task_struct *parent);
 int security_capget(const struct task_struct *target,
@@ -538,7 +538,7 @@ static inline int security_binder_transfer_binder(const struct cred *from,
 
 static inline int security_binder_transfer_file(const struct cred *from,
 						const struct cred *to,
-						struct file *file)
+						const struct file *file)
 {
 	return 0;
 }

security/security.c

@@ -841,7 +841,7 @@ int security_binder_transfer_binder(const struct cred *from,
  * Return: Returns 0 if permission is granted.
  */
 int security_binder_transfer_file(const struct cred *from,
-				  const struct cred *to, struct file *file)
+				  const struct cred *to, const struct file *file)
 {
 	return call_int_hook(binder_transfer_file, 0, from, to, file);
 }

security/selinux/hooks.c

@@ -1691,7 +1691,7 @@ static inline int file_path_has_perm(const struct cred *cred,
 }
 
 #ifdef CONFIG_BPF_SYSCALL
-static int bpf_fd_pass(struct file *file, u32 sid);
+static int bpf_fd_pass(const struct file *file, u32 sid);
 #endif
 
 /* Check whether a task can use an open file descriptor to
@@ -1952,7 +1952,7 @@ static inline u32 file_mask_to_av(int mode, int mask)
 }
 
 /* Convert a Linux file to an access vector. */
-static inline u32 file_to_av(struct file *file)
+static inline u32 file_to_av(const struct file *file)
 {
 	u32 av = 0;
 
@@ -2027,7 +2027,7 @@ static int selinux_binder_transfer_binder(const struct cred *from,
 
 static int selinux_binder_transfer_file(const struct cred *from,
 					const struct cred *to,
-					struct file *file)
+					const struct file *file)
 {
 	u32 sid = cred_sid(to);
 	struct file_security_struct *fsec = selinux_file(file);
@@ -6718,7 +6718,7 @@ static u32 bpf_map_fmode_to_av(fmode_t fmode)
  * access the bpf object and that's why we have to add this additional check in
  * selinux_file_receive and selinux_binder_transfer_files.
  */
-static int bpf_fd_pass(struct file *file, u32 sid)
+static int bpf_fd_pass(const struct file *file, u32 sid)
 {
 	struct bpf_security_struct *bpfsec;
 	struct bpf_prog *prog;