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linux/arch/h8300/kernel/signal.c
David Howells ee18d64c1f KEYS: Add a keyctl to install a process's session keyring on its parent [try #6] 
Add a keyctl to install a process's session keyring onto its parent.  This
replaces the parent's session keyring.  Because the COW credential code does
not permit one process to change another process's credentials directly, the
change is deferred until userspace next starts executing again.  Normally this
will be after a wait*() syscall.

To support this, three new security hooks have been provided:
cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in
the blank security creds and key_session_to_parent() - which asks the LSM if
the process may replace its parent's session keyring.

The replacement may only happen if the process has the same ownership details
as its parent, and the process has LINK permission on the session keyring, and
the session keyring is owned by the process, and the LSM permits it.

Note that this requires alteration to each architecture's notify_resume path.
This has been done for all arches barring blackfin, m68k* and xtensa, all of
which need assembly alteration to support TIF_NOTIFY_RESUME.  This allows the
replacement to be performed at the point the parent process resumes userspace
execution.

This allows the userspace AFS pioctl emulation to fully emulate newpag() and
the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to
alter the parent process's PAG membership.  However, since kAFS doesn't use
PAGs per se, but rather dumps the keys into the session keyring, the session
keyring of the parent must be replaced if, for example, VIOCSETTOK is passed
the newpag flag.

This can be tested with the following program:

	#include <stdio.h>
	#include <stdlib.h>
	#include <keyutils.h>

	#define KEYCTL_SESSION_TO_PARENT	18

	#define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0)

	int main(int argc, char **argv)
	{
		key_serial_t keyring, key;
		long ret;

		keyring = keyctl_join_session_keyring(argv[1]);
		OSERROR(keyring, "keyctl_join_session_keyring");

		key = add_key("user", "a", "b", 1, keyring);
		OSERROR(key, "add_key");

		ret = keyctl(KEYCTL_SESSION_TO_PARENT);
		OSERROR(ret, "KEYCTL_SESSION_TO_PARENT");

		return 0;
	}

Compiled and linked with -lkeyutils, you should see something like:

	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: _ses
	355907932 --alswrv   4043    -1   \_ keyring: _uid.4043
	[dhowells@andromeda ~]$ /tmp/newpag
	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: _ses
	1055658746 --alswrv   4043  4043   \_ user: a
	[dhowells@andromeda ~]$ /tmp/newpag hello
	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: hello
	340417692 --alswrv   4043  4043   \_ user: a

Where the test program creates a new session keyring, sticks a user key named
'a' into it and then installs it on its parent.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-09-02 21:29:22 +10:00

563 lines
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/*
* linux/arch/h8300/kernel/signal.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of this archive
* for more details.
*/
/*
* uClinux H8/300 support by Yoshinori Sato <ysato@users.sourceforge.jp>
* and David McCullough <davidm@snapgear.com>
*
* Based on
* Linux/m68k by Hamish Macdonald
*/
/*
* ++roman (07/09/96): implemented signal stacks (specially for tosemu on
* Atari :-) Current limitation: Only one sigstack can be active at one time.
* If a second signal with SA_ONSTACK set arrives while working on a sigstack,
* SA_ONSTACK is ignored. This behaviour avoids lots of trouble with nested
* signal handlers!
*/
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/syscalls.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/highuid.h>
#include <linux/personality.h>
#include <linux/tty.h>
#include <linux/binfmts.h>
#include <linux/freezer.h>
#include <asm/setup.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/traps.h>
#include <asm/ucontext.h>
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
asmlinkage int do_signal(struct pt_regs *regs, sigset_t *oldset);
/*
* Atomically swap in the new signal mask, and wait for a signal.
*/
asmlinkage int do_sigsuspend(struct pt_regs *regs)
{
old_sigset_t mask = regs->er3;
sigset_t saveset;
mask &= _BLOCKABLE;
spin_lock_irq(&current->sighand->siglock);
saveset = current->blocked;
siginitset(&current->blocked, mask);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
regs->er0 = -EINTR;
while (1) {
current->state = TASK_INTERRUPTIBLE;
schedule();
if (do_signal(regs, &saveset))
return -EINTR;
}
}
asmlinkage int
do_rt_sigsuspend(struct pt_regs *regs)
{
sigset_t *unewset = (sigset_t *)regs->er1;
size_t sigsetsize = (size_t)regs->er2;
sigset_t saveset, newset;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (copy_from_user(&newset, unewset, sizeof(newset)))
return -EFAULT;
sigdelsetmask(&newset, ~_BLOCKABLE);
spin_lock_irq(&current->sighand->siglock);
saveset = current->blocked;
current->blocked = newset;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
regs->er0 = -EINTR;
while (1) {
current->state = TASK_INTERRUPTIBLE;
schedule();
if (do_signal(regs, &saveset))
return -EINTR;
}
}
asmlinkage int
sys_sigaction(int sig, const struct old_sigaction *act,
struct old_sigaction *oact)
{
struct k_sigaction new_ka, old_ka;
int ret;
if (act) {
old_sigset_t mask;
if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
__get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
__get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
return -EFAULT;
__get_user(new_ka.sa.sa_flags, &act->sa_flags);
__get_user(mask, &act->sa_mask);
siginitset(&new_ka.sa.sa_mask, mask);
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
__put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
__put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
return -EFAULT;
__put_user(old_ka.sa.sa_flags, &oact->sa_flags);
__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
}
return ret;
}
asmlinkage int
sys_sigaltstack(const stack_t *uss, stack_t *uoss)
{
return do_sigaltstack(uss, uoss, rdusp());
}
/*
* Do a signal return; undo the signal stack.
*
* Keep the return code on the stack quadword aligned!
* That makes the cache flush below easier.
*/
struct sigframe
{
long dummy_er0;
long dummy_vector;
#if defined(CONFIG_CPU_H8S)
short dummy_exr;
#endif
long dummy_pc;
char *pretcode;
unsigned char retcode[8];
unsigned long extramask[_NSIG_WORDS-1];
struct sigcontext sc;
int sig;
} __attribute__((aligned(2),packed));
struct rt_sigframe
{
long dummy_er0;
long dummy_vector;
#if defined(CONFIG_CPU_H8S)
short dummy_exr;
#endif
long dummy_pc;
char *pretcode;
struct siginfo *pinfo;
void *puc;
unsigned char retcode[8];
struct siginfo info;
struct ucontext uc;
int sig;
} __attribute__((aligned(2),packed));
static inline int
restore_sigcontext(struct pt_regs *regs, struct sigcontext *usc,
int *pd0)
{
int err = 0;
unsigned int ccr;
unsigned int usp;
unsigned int er0;
/* Always make any pending restarted system calls return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
#define COPY(r) err |= __get_user(regs->r, &usc->sc_##r) /* restore passed registers */
COPY(er1);
COPY(er2);
COPY(er3);
COPY(er5);
COPY(pc);
ccr = regs->ccr & 0x10;
COPY(ccr);
#undef COPY
regs->ccr &= 0xef;
regs->ccr |= ccr;
regs->orig_er0 = -1; /* disable syscall checks */
err |= __get_user(usp, &usc->sc_usp);
wrusp(usp);
err |= __get_user(er0, &usc->sc_er0);
*pd0 = er0;
return err;
}
asmlinkage int do_sigreturn(unsigned long __unused,...)
{
struct pt_regs *regs = (struct pt_regs *) (&__unused - 1);
unsigned long usp = rdusp();
struct sigframe *frame = (struct sigframe *)(usp - 4);
sigset_t set;
int er0;
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
if (__get_user(set.sig[0], &frame->sc.sc_mask) ||
(_NSIG_WORDS > 1 &&
__copy_from_user(&set.sig[1], &frame->extramask,
sizeof(frame->extramask))))
goto badframe;
sigdelsetmask(&set, ~_BLOCKABLE);
spin_lock_irq(&current->sighand->siglock);
current->blocked = set;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
if (restore_sigcontext(regs, &frame->sc, &er0))
goto badframe;
return er0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
asmlinkage int do_rt_sigreturn(unsigned long __unused,...)
{
struct pt_regs *regs = (struct pt_regs *) &__unused;
unsigned long usp = rdusp();
struct rt_sigframe *frame = (struct rt_sigframe *)(usp - 4);
sigset_t set;
int er0;
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
goto badframe;
sigdelsetmask(&set, ~_BLOCKABLE);
spin_unlock_irq(&current->sighand->siglock);
current->blocked = set;
recalc_sigpending();
spin_lock_irq(&current->sighand->siglock);
if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &er0))
goto badframe;
if (do_sigaltstack(&frame->uc.uc_stack, NULL, usp) == -EFAULT)
goto badframe;
return er0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
static int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
unsigned long mask)
{
int err = 0;
err |= __put_user(regs->er0, &sc->sc_er0);
err |= __put_user(regs->er1, &sc->sc_er1);
err |= __put_user(regs->er2, &sc->sc_er2);
err |= __put_user(regs->er3, &sc->sc_er3);
err |= __put_user(regs->er4, &sc->sc_er4);
err |= __put_user(regs->er5, &sc->sc_er5);
err |= __put_user(regs->er6, &sc->sc_er6);
err |= __put_user(rdusp(), &sc->sc_usp);
err |= __put_user(regs->pc, &sc->sc_pc);
err |= __put_user(regs->ccr, &sc->sc_ccr);
err |= __put_user(mask, &sc->sc_mask);
return err;
}
static inline void *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
{
unsigned long usp;
/* Default to using normal stack. */
usp = rdusp();
/* This is the X/Open sanctioned signal stack switching. */
if (ka->sa.sa_flags & SA_ONSTACK) {
if (!sas_ss_flags(usp))
usp = current->sas_ss_sp + current->sas_ss_size;
}
return (void *)((usp - frame_size) & -8UL);
}
static void setup_frame (int sig, struct k_sigaction *ka,
sigset_t *set, struct pt_regs *regs)
{
struct sigframe *frame;
int err = 0;
int usig;
unsigned char *ret;
frame = get_sigframe(ka, regs, sizeof(*frame));
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto give_sigsegv;
usig = current_thread_info()->exec_domain
&& current_thread_info()->exec_domain->signal_invmap
&& sig < 32
? current_thread_info()->exec_domain->signal_invmap[sig]
: sig;
err |= __put_user(usig, &frame->sig);
if (err)
goto give_sigsegv;
err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
if (err)
goto give_sigsegv;
if (_NSIG_WORDS > 1) {
err |= copy_to_user(frame->extramask, &set->sig[1],
sizeof(frame->extramask));
if (err)
goto give_sigsegv;
}
ret = frame->retcode;
if (ka->sa.sa_flags & SA_RESTORER)
ret = (unsigned char *)(ka->sa.sa_restorer);
else {
/* sub.l er0,er0; mov.b #__NR_sigreturn,r0l; trapa #0 */
err |= __put_user(0x1a80f800 + (__NR_sigreturn & 0xff),
(unsigned long *)(frame->retcode + 0));
err |= __put_user(0x5700, (unsigned short *)(frame->retcode + 4));
}
/* Set up to return from userspace. */
err |= __put_user(ret, &frame->pretcode);
if (err)
goto give_sigsegv;
/* Set up registers for signal handler */
wrusp ((unsigned long) frame);
regs->pc = (unsigned long) ka->sa.sa_handler;
regs->er0 = (current_thread_info()->exec_domain
&& current_thread_info()->exec_domain->signal_invmap
&& sig < 32
? current_thread_info()->exec_domain->signal_invmap[sig]
: sig);
regs->er1 = (unsigned long)&(frame->sc);
regs->er5 = current->mm->start_data; /* GOT base */
return;
give_sigsegv:
force_sigsegv(sig, current);
}
static void setup_rt_frame (int sig, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs *regs)
{
struct rt_sigframe *frame;
int err = 0;
int usig;
unsigned char *ret;
frame = get_sigframe(ka, regs, sizeof(*frame));
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto give_sigsegv;
usig = current_thread_info()->exec_domain
&& current_thread_info()->exec_domain->signal_invmap
&& sig < 32
? current_thread_info()->exec_domain->signal_invmap[sig]
: sig;
err |= __put_user(usig, &frame->sig);
if (err)
goto give_sigsegv;
err |= __put_user(&frame->info, &frame->pinfo);
err |= __put_user(&frame->uc, &frame->puc);
err |= copy_siginfo_to_user(&frame->info, info);
if (err)
goto give_sigsegv;
/* Create the ucontext. */
err |= __put_user(0, &frame->uc.uc_flags);
err |= __put_user(0, &frame->uc.uc_link);
err |= __put_user((void *)current->sas_ss_sp,
&frame->uc.uc_stack.ss_sp);
err |= __put_user(sas_ss_flags(rdusp()),
&frame->uc.uc_stack.ss_flags);
err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
err |= copy_to_user (&frame->uc.uc_sigmask, set, sizeof(*set));
if (err)
goto give_sigsegv;
/* Set up to return from userspace. */
ret = frame->retcode;
if (ka->sa.sa_flags & SA_RESTORER)
ret = (unsigned char *)(ka->sa.sa_restorer);
else {
/* sub.l er0,er0; mov.b #__NR_sigreturn,r0l; trapa #0 */
err |= __put_user(0x1a80f800 + (__NR_sigreturn & 0xff),
(unsigned long *)(frame->retcode + 0));
err |= __put_user(0x5700, (unsigned short *)(frame->retcode + 4));
}
err |= __put_user(ret, &frame->pretcode);
if (err)
goto give_sigsegv;
/* Set up registers for signal handler */
wrusp ((unsigned long) frame);
regs->pc = (unsigned long) ka->sa.sa_handler;
regs->er0 = (current_thread_info()->exec_domain
&& current_thread_info()->exec_domain->signal_invmap
&& sig < 32
? current_thread_info()->exec_domain->signal_invmap[sig]
: sig);
regs->er1 = (unsigned long)&(frame->info);
regs->er2 = (unsigned long)&frame->uc;
regs->er5 = current->mm->start_data; /* GOT base */
return;
give_sigsegv:
force_sigsegv(sig, current);
}
/*
* OK, we're invoking a handler
*/
static void
handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
sigset_t *oldset, struct pt_regs * regs)
{
/* are we from a system call? */
if (regs->orig_er0 >= 0) {
switch (regs->er0) {
case -ERESTART_RESTARTBLOCK:
case -ERESTARTNOHAND:
regs->er0 = -EINTR;
break;
case -ERESTARTSYS:
if (!(ka->sa.sa_flags & SA_RESTART)) {
regs->er0 = -EINTR;
break;
}
/* fallthrough */
case -ERESTARTNOINTR:
regs->er0 = regs->orig_er0;
regs->pc -= 2;
}
}
/* set up the stack frame */
if (ka->sa.sa_flags & SA_SIGINFO)
setup_rt_frame(sig, ka, info, oldset, regs);
else
setup_frame(sig, ka, oldset, regs);
spin_lock_irq(&current->sighand->siglock);
sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
if (!(ka->sa.sa_flags & SA_NODEFER))
sigaddset(&current->blocked,sig);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
}
/*
* Note that 'init' is a special process: it doesn't get signals it doesn't
* want to handle. Thus you cannot kill init even with a SIGKILL even by
* mistake.
*/
asmlinkage int do_signal(struct pt_regs *regs, sigset_t *oldset)
{
siginfo_t info;
int signr;
struct k_sigaction ka;
/*
* We want the common case to go fast, which
* is why we may in certain cases get here from
* kernel mode. Just return without doing anything
* if so.
*/
if ((regs->ccr & 0x10))
return 1;
if (try_to_freeze())
goto no_signal;
current->thread.esp0 = (unsigned long) regs;
if (!oldset)
oldset = &current->blocked;
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
/* Whee! Actually deliver the signal. */
handle_signal(signr, &info, &ka, oldset, regs);
return 1;
}
no_signal:
/* Did we come from a system call? */
if (regs->orig_er0 >= 0) {
/* Restart the system call - no handlers present */
if (regs->er0 == -ERESTARTNOHAND ||
regs->er0 == -ERESTARTSYS ||
regs->er0 == -ERESTARTNOINTR) {
regs->er0 = regs->orig_er0;
regs->pc -= 2;
}
if (regs->er0 == -ERESTART_RESTARTBLOCK){
regs->er0 = __NR_restart_syscall;
regs->pc -= 2;
}
}
return 0;
}
asmlinkage void do_notify_resume(struct pt_regs *regs, u32 thread_info_flags)
{
if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
do_signal(regs, NULL);
if (thread_info_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
tracehook_notify_resume(regs);
if (current->replacement_session_keyring)
key_replace_session_keyring();
}
}
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