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Subject[PATCH v9 2/4] seccomp: switch system call argument type to void *
Date
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: Tycho 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>
CC: Christian Brauner <christian@brauner.io>
CC: Tyler Hicks <tyhicks@canonical.com>
CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
---
include/linux/seccomp.h | 2 +-
kernel/seccomp.c | 8 ++++----
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index e5320f6c8654..b5103c019cf4 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -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)
{
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 96afc32e041d..393e029f778a 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -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:
--
2.19.1
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