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kernel: provide ksys_*() wrappers for syscalls called by kernel/uid16.c

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Using these helpers allows us to avoid the in-kernel calls to these
syscalls: sys_setregid(), sys_setgid(), sys_setreuid(), sys_setuid(),
sys_setresuid(), sys_setresgid(), sys_setfsuid(), and sys_setfsgid().

The ksys_ prefix denotes that these function are meant as a drop-in
replacement for the syscall. In particular, they use the same calling
convention.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
This commit is contained in:
Dominik Brodowski 2018-03-19 18:09:27 +01:00
parent 6203deb0a7
commit e530dca584
3 changed files with 74 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
kernel/sys.c
View File

@ -69,6 +69,8 @@
#include <asm/io.h>
#include <asm/unistd.h>
#include "uid16.h"
#ifndef SET_UNALIGN_CTL
# define SET_UNALIGN_CTL(a, b) (-EINVAL)
#endif
@ -340,7 +342,7 @@ out_unlock:
* operations (as far as semantic preservation is concerned).
*/
#ifdef CONFIG_MULTIUSER
SYSCALL_DEFINE2(setregid, gid_t, rgid, gid_t, egid)
long __sys_setregid(gid_t rgid, gid_t egid)
{
struct user_namespace *ns = current_user_ns();
const struct cred *old;
@ -392,12 +394,17 @@ error:
return retval;
}
SYSCALL_DEFINE2(setregid, gid_t, rgid, gid_t, egid)
{
return __sys_setregid(rgid, egid);
}
/*
* setgid() is implemented like SysV w/ SAVED_IDS
*
* SMP: Same implicit races as above.
*/
SYSCALL_DEFINE1(setgid, gid_t, gid)
long __sys_setgid(gid_t gid)
{
struct user_namespace *ns = current_user_ns();
const struct cred *old;
@ -429,6 +436,11 @@ error:
return retval;
}
SYSCALL_DEFINE1(setgid, gid_t, gid)
{
return __sys_setgid(gid);
}
/*
* change the user struct in a credentials set to match the new UID
*/
@ -473,7 +485,7 @@ static int set_user(struct cred *new)
* 100% compatible with BSD. A program which uses just setuid() will be
* 100% compatible with POSIX with saved IDs.
*/
SYSCALL_DEFINE2(setreuid, uid_t, ruid, uid_t, euid)
long __sys_setreuid(uid_t ruid, uid_t euid)
{
struct user_namespace *ns = current_user_ns();
const struct cred *old;
@ -533,6 +545,11 @@ error:
return retval;
}
SYSCALL_DEFINE2(setreuid, uid_t, ruid, uid_t, euid)
{
return __sys_setreuid(ruid, euid);
}
/*
* setuid() is implemented like SysV with SAVED_IDS
*
@ -544,7 +561,7 @@ error:
* will allow a root program to temporarily drop privileges and be able to
* regain them by swapping the real and effective uid.
*/
SYSCALL_DEFINE1(setuid, uid_t, uid)
long __sys_setuid(uid_t uid)
{
struct user_namespace *ns = current_user_ns();
const struct cred *old;
@ -586,12 +603,17 @@ error:
return retval;
}
SYSCALL_DEFINE1(setuid, uid_t, uid)
{
return __sys_setuid(uid);
}
/*
* This function implements a generic ability to update ruid, euid,
* and suid. This allows you to implement the 4.4 compatible seteuid().
*/
SYSCALL_DEFINE3(setresuid, uid_t, ruid, uid_t, euid, uid_t, suid)
long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
{
struct user_namespace *ns = current_user_ns();
const struct cred *old;
@ -656,6 +678,11 @@ error:
return retval;
}
SYSCALL_DEFINE3(setresuid, uid_t, ruid, uid_t, euid, uid_t, suid)
{
return __sys_setresuid(ruid, euid, suid);
}
SYSCALL_DEFINE3(getresuid, uid_t __user *, ruidp, uid_t __user *, euidp, uid_t __user *, suidp)
{
const struct cred *cred = current_cred();
@ -678,7 +705,7 @@ SYSCALL_DEFINE3(getresuid, uid_t __user *, ruidp, uid_t __user *, euidp, uid_t _
/*
* Same as above, but for rgid, egid, sgid.
*/
SYSCALL_DEFINE3(setresgid, gid_t, rgid, gid_t, egid, gid_t, sgid)
long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid)
{
struct user_namespace *ns = current_user_ns();
const struct cred *old;
@ -730,6 +757,11 @@ error:
return retval;
}
SYSCALL_DEFINE3(setresgid, gid_t, rgid, gid_t, egid, gid_t, sgid)
{
return __sys_setresgid(rgid, egid, sgid);
}
SYSCALL_DEFINE3(getresgid, gid_t __user *, rgidp, gid_t __user *, egidp, gid_t __user *, sgidp)
{
const struct cred *cred = current_cred();
@ -757,7 +789,7 @@ SYSCALL_DEFINE3(getresgid, gid_t __user *, rgidp, gid_t __user *, egidp, gid_t _
* whatever uid it wants to). It normally shadows "euid", except when
* explicitly set by setfsuid() or for access..
*/
SYSCALL_DEFINE1(setfsuid, uid_t, uid)
long __sys_setfsuid(uid_t uid)
{
const struct cred *old;
struct cred *new;
@ -793,10 +825,15 @@ change_okay:
return old_fsuid;
}
SYSCALL_DEFINE1(setfsuid, uid_t, uid)
{
return __sys_setfsuid(uid);
}
/*
* Samma på svenska..
*/
SYSCALL_DEFINE1(setfsgid, gid_t, gid)
long __sys_setfsgid(gid_t gid)
{
const struct cred *old;
struct cred *new;
@ -830,6 +867,11 @@ change_okay:
commit_creds(new);
return old_fsgid;
}
SYSCALL_DEFINE1(setfsgid, gid_t, gid)
{
return __sys_setfsgid(gid);
}
#endif /* CONFIG_MULTIUSER */
/**

19
kernel/uid16.c
View File

@ -18,6 +18,8 @@
#include <linux/uaccess.h>
#include "uid16.h"
SYSCALL_DEFINE3(chown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
{
return sys_chown(filename, low2highuid(user), low2highgid(group));
@ -35,27 +37,27 @@ SYSCALL_DEFINE3(fchown16, unsigned int, fd, old_uid_t, user, old_gid_t, group)
SYSCALL_DEFINE2(setregid16, old_gid_t, rgid, old_gid_t, egid)
{
return sys_setregid(low2highgid(rgid), low2highgid(egid));
return __sys_setregid(low2highgid(rgid), low2highgid(egid));
}
SYSCALL_DEFINE1(setgid16, old_gid_t, gid)
{
return sys_setgid(low2highgid(gid));
return __sys_setgid(low2highgid(gid));
}
SYSCALL_DEFINE2(setreuid16, old_uid_t, ruid, old_uid_t, euid)
{
return sys_setreuid(low2highuid(ruid), low2highuid(euid));
return __sys_setreuid(low2highuid(ruid), low2highuid(euid));
}
SYSCALL_DEFINE1(setuid16, old_uid_t, uid)
{
return sys_setuid(low2highuid(uid));
return __sys_setuid(low2highuid(uid));
}
SYSCALL_DEFINE3(setresuid16, old_uid_t, ruid, old_uid_t, euid, old_uid_t, suid)
{
return sys_setresuid(low2highuid(ruid), low2highuid(euid),
return __sys_setresuid(low2highuid(ruid), low2highuid(euid),
low2highuid(suid));
}
@ -78,11 +80,10 @@ SYSCALL_DEFINE3(getresuid16, old_uid_t __user *, ruidp, old_uid_t __user *, euid
SYSCALL_DEFINE3(setresgid16, old_gid_t, rgid, old_gid_t, egid, old_gid_t, sgid)
{
return sys_setresgid(low2highgid(rgid), low2highgid(egid),
return __sys_setresgid(low2highgid(rgid), low2highgid(egid),
low2highgid(sgid));
}
SYSCALL_DEFINE3(getresgid16, old_gid_t __user *, rgidp, old_gid_t __user *, egidp, old_gid_t __user *, sgidp)
{
const struct cred *cred = current_cred();
@ -102,12 +103,12 @@ SYSCALL_DEFINE3(getresgid16, old_gid_t __user *, rgidp, old_gid_t __user *, egid
SYSCALL_DEFINE1(setfsuid16, old_uid_t, uid)
{
return sys_setfsuid(low2highuid(uid));
return __sys_setfsuid(low2highuid(uid));
}
SYSCALL_DEFINE1(setfsgid16, old_gid_t, gid)
{
return sys_setfsgid(low2highgid(gid));
return __sys_setfsgid(low2highgid(gid));
}
static int groups16_to_user(old_gid_t __user *grouplist,

14
kernel/uid16.h Normal file
View File

@ -0,0 +1,14 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef LINUX_UID16_H
#define LINUX_UID16_H
long __sys_setuid(uid_t uid);
long __sys_setgid(gid_t gid);
long __sys_setreuid(uid_t ruid, uid_t euid);
long __sys_setregid(gid_t rgid, gid_t egid);
long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid);
long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid);
long __sys_setfsuid(uid_t uid);
long __sys_setfsgid(gid_t gid);
#endif /* LINUX_UID16_H */