Commit a5662e4d authored by Tycho Andersen's avatar Tycho Andersen Committed by Kees Cook
Browse files

seccomp: switch system call argument type to void * 



The const qualifier causes problems for any code that wants to write to the
third argument of the seccomp syscall, as we will do in a future patch in
this series.

The third argument to the seccomp syscall is documented as void *, so
rather than just dropping the const, let's switch everything to use void *
as well.

I believe this is safe because of 1. the documentation above, 2. there's no
real type information exported about syscalls anywhere besides the man
pages.

Signed-off-by: default avatarTycho Andersen <tycho@tycho.ws>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Eric W. Biederman <ebiederm@xmission.com>
CC: "Serge E. Hallyn" <serge@hallyn.com>
Acked-by: default avatarSerge Hallyn <serge@hallyn.com>
CC: Christian Brauner <christian@brauner.io>
CC: Tyler Hicks <tyhicks@canonical.com>
CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent db511391

include/linux/seccomp.h

+1 −1
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ extern void secure_computing_strict(int this_syscall); 
#endif



extern long prctl_get_seccomp(void);

extern long prctl_set_seccomp(unsigned long, char __user *);

extern long prctl_set_seccomp(unsigned long, void __user *);



static inline int seccomp_mode(struct seccomp *s)

{

include/linux/syscalls.h

+1 −1
Original line number Diff line number Diff line
@@ -879,7 +879,7 @@ asmlinkage long sys_renameat2(int olddfd, const char __user *oldname, 
			      int newdfd, const char __user *newname,

			      unsigned int flags);

asmlinkage long sys_seccomp(unsigned int op, unsigned int flags,

			    const char __user *uargs);

			    void __user *uargs);

asmlinkage long sys_getrandom(char __user *buf, size_t count,

			      unsigned int flags);

asmlinkage long sys_memfd_create(const char __user *uname_ptr, unsigned int flags);

kernel/seccomp.c

+4 −4
Original line number Diff line number Diff line
@@ -924,7 +924,7 @@ static long seccomp_get_action_avail(const char __user *uaction) 


/* Common entry point for both prctl and syscall. */

static long do_seccomp(unsigned int op, unsigned int flags,

		       const char __user *uargs)

		       void __user *uargs)

{

	switch (op) {

	case SECCOMP_SET_MODE_STRICT:
@@ -944,7 +944,7 @@ static long do_seccomp(unsigned int op, unsigned int flags, 
}



SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,

			 const char __user *, uargs)

			 void __user *, uargs)

{

	return do_seccomp(op, flags, uargs);

}
@@ -956,10 +956,10 @@ SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, 
 *

 * Returns 0 on success or -EINVAL on failure.

 */

long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)

long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)

{

	unsigned int op;

	char __user *uargs;

	void __user *uargs;



	switch (seccomp_mode) {

	case SECCOMP_MODE_STRICT:

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