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Subject[PATCH 22/45] kernel: provide ksys_*() wrappers for syscalls called by kernel/uid16.c
Date
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 tries to remove in-kernel calls to
syscalls. On this basis, the syscall entry path can be streamlined.

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>
---
kernel/sys.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++--------
kernel/uid16.c | 19 ++++++++++---------
kernel/uid16.h | 14 ++++++++++++++
3 files changed, 74 insertions(+), 17 deletions(-)
create mode 100644 kernel/uid16.h

diff --git a/kernel/sys.c b/kernel/sys.c
index 8eda25dcbbd4..ad692183dfe9 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -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 */

/**
diff --git a/kernel/uid16.c b/kernel/uid16.c
index ea3cf87ff000..af6925d8599b 100644
--- a/kernel/uid16.c
+++ b/kernel/uid16.c
@@ -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 ksys_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,
diff --git a/kernel/uid16.h b/kernel/uid16.h
new file mode 100644
index 000000000000..cdca040f7602
--- /dev/null
+++ b/kernel/uid16.h
@@ -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 */
--
2.16.2
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