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@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> --- 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 ebb138b841c8..550f47788ae4 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 ef1da2a5f9bd..7b930edfe461 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 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, 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 */ -- 2.16.3
