Commit e530dca5 authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

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

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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 6203deb0

kernel/sys.c

+50 −8
Original line number Diff line number Diff line
@@ -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 @@ SYSCALL_DEFINE2(getpriority, int, which, int, who) 
 *      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 @@ SYSCALL_DEFINE2(setregid, gid_t, rgid, gid_t, egid) 
	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 @@ SYSCALL_DEFINE1(setgid, gid_t, gid) 
	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 @@ SYSCALL_DEFINE2(setreuid, uid_t, ruid, uid_t, euid) 
	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 @@ SYSCALL_DEFINE2(setreuid, uid_t, ruid, uid_t, euid) 
 * 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 @@ SYSCALL_DEFINE1(setuid, uid_t, uid) 
	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 @@ SYSCALL_DEFINE3(setresuid, uid_t, ruid, uid_t, euid, uid_t, suid) 
	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 @@ SYSCALL_DEFINE3(setresgid, gid_t, rgid, gid_t, egid, gid_t, sgid) 
	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 @@ SYSCALL_DEFINE1(setfsuid, uid_t, uid) 
	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 @@ SYSCALL_DEFINE1(setfsgid, gid_t, gid) 
	commit_creds(new);

	return old_fsgid;

}



SYSCALL_DEFINE1(setfsgid, gid_t, gid)

{

	return __sys_setfsgid(gid);

}

#endif /* CONFIG_MULTIUSER */



/**

kernel/uid16.c

+10 −9
Original line number Diff line number Diff line
@@ -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,

kernel/uid16.h

0 → 100644
+14 −0
Original line number Diff line number Diff line 
/* 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 */