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linux/arch/mn10300/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

575 lines
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/* MN10300 Signal handling
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/personality.h>
#include <linux/suspend.h>
#include <linux/tracehook.h>
#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/fpu.h>
#include "sigframe.h"
#define DEBUG_SIG 0
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
/*
* atomically swap in the new signal mask, and wait for a signal.
*/
asmlinkage long sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
mask &= _BLOCKABLE;
spin_lock_irq(&current->sighand->siglock);
current->saved_sigmask = current->blocked;
siginitset(&current->blocked, mask);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
current->state = TASK_INTERRUPTIBLE;
schedule();
set_thread_flag(TIF_RESTORE_SIGMASK);
return -ERESTARTNOHAND;
}
/*
* set signal action syscall
*/
asmlinkage long sys_sigaction(int sig,
const struct old_sigaction __user *act,
struct old_sigaction __user *oact)
{
struct k_sigaction new_ka, old_ka;
int ret;
if (act) {
old_sigset_t mask;
if (verify_area(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 (verify_area(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;
}
/*
* set alternate signal stack syscall
*/
asmlinkage long sys_sigaltstack(const stack_t __user *uss, stack_t *uoss)
{
return do_sigaltstack(uss, uoss, __frame->sp);
}
/*
* do a signal return; undo the signal stack.
*/
static int restore_sigcontext(struct pt_regs *regs,
struct sigcontext __user *sc, long *_d0)
{
unsigned int err = 0;
if (is_using_fpu(current))
fpu_kill_state(current);
#define COPY(x) err |= __get_user(regs->x, &sc->x)
COPY(d1); COPY(d2); COPY(d3);
COPY(a0); COPY(a1); COPY(a2); COPY(a3);
COPY(e0); COPY(e1); COPY(e2); COPY(e3);
COPY(e4); COPY(e5); COPY(e6); COPY(e7);
COPY(lar); COPY(lir);
COPY(mdr); COPY(mdrq);
COPY(mcvf); COPY(mcrl); COPY(mcrh);
COPY(sp); COPY(pc);
#undef COPY
{
unsigned int tmpflags;
#ifndef CONFIG_MN10300_USING_JTAG
#define USER_EPSW (EPSW_FLAG_Z | EPSW_FLAG_N | EPSW_FLAG_C | EPSW_FLAG_V | \
EPSW_T | EPSW_nAR)
#else
#define USER_EPSW (EPSW_FLAG_Z | EPSW_FLAG_N | EPSW_FLAG_C | EPSW_FLAG_V | \
EPSW_nAR)
#endif
err |= __get_user(tmpflags, &sc->epsw);
regs->epsw = (regs->epsw & ~USER_EPSW) |
(tmpflags & USER_EPSW);
regs->orig_d0 = -1; /* disable syscall checks */
}
{
struct fpucontext *buf;
err |= __get_user(buf, &sc->fpucontext);
if (buf) {
if (verify_area(VERIFY_READ, buf, sizeof(*buf)))
goto badframe;
err |= fpu_restore_sigcontext(buf);
}
}
err |= __get_user(*_d0, &sc->d0);
return err;
badframe:
return 1;
}
/*
* standard signal return syscall
*/
asmlinkage long sys_sigreturn(void)
{
struct sigframe __user *frame = (struct sigframe __user *) __frame->sp;
sigset_t set;
long d0;
if (verify_area(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
if (__get_user(set.sig[0], &frame->sc.oldmask))
goto badframe;
if (_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(__frame, &frame->sc, &d0))
goto badframe;
return d0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
/*
* realtime signal return syscall
*/
asmlinkage long sys_rt_sigreturn(void)
{
struct rt_sigframe __user *frame =
(struct rt_sigframe __user *) __frame->sp;
sigset_t set;
unsigned long d0;
if (verify_area(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
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(__frame, &frame->uc.uc_mcontext, &d0))
goto badframe;
if (do_sigaltstack(&frame->uc.uc_stack, NULL, __frame->sp) == -EFAULT)
goto badframe;
return d0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
/*
* store the userspace context into a signal frame
*/
static int setup_sigcontext(struct sigcontext __user *sc,
struct fpucontext *fpuctx,
struct pt_regs *regs,
unsigned long mask)
{
int tmp, err = 0;
#define COPY(x) err |= __put_user(regs->x, &sc->x)
COPY(d0); COPY(d1); COPY(d2); COPY(d3);
COPY(a0); COPY(a1); COPY(a2); COPY(a3);
COPY(e0); COPY(e1); COPY(e2); COPY(e3);
COPY(e4); COPY(e5); COPY(e6); COPY(e7);
COPY(lar); COPY(lir);
COPY(mdr); COPY(mdrq);
COPY(mcvf); COPY(mcrl); COPY(mcrh);
COPY(sp); COPY(epsw); COPY(pc);
#undef COPY
tmp = fpu_setup_sigcontext(fpuctx);
if (tmp < 0)
err = 1;
else
err |= __put_user(tmp ? fpuctx : NULL, &sc->fpucontext);
/* non-iBCS2 extensions.. */
err |= __put_user(mask, &sc->oldmask);
return err;
}
/*
* determine which stack to use..
*/
static inline void __user *get_sigframe(struct k_sigaction *ka,
struct pt_regs *regs,
size_t frame_size)
{
unsigned long sp;
/* default to using normal stack */
sp = regs->sp;
/* this is the X/Open sanctioned signal stack switching. */
if (ka->sa.sa_flags & SA_ONSTACK) {
if (!on_sig_stack(sp))
sp = current->sas_ss_sp + current->sas_ss_size;
}
return (void __user *) ((sp - frame_size) & ~7UL);
}
/*
* set up a normal signal frame
*/
static int setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
struct pt_regs *regs)
{
struct sigframe __user *frame;
int rsig;
frame = get_sigframe(ka, regs, sizeof(*frame));
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto give_sigsegv;
rsig = sig;
if (sig < 32 &&
current_thread_info()->exec_domain &&
current_thread_info()->exec_domain->signal_invmap)
rsig = current_thread_info()->exec_domain->signal_invmap[sig];
if (__put_user(rsig, &frame->sig) < 0 ||
__put_user(&frame->sc, &frame->psc) < 0)
goto give_sigsegv;
if (setup_sigcontext(&frame->sc, &frame->fpuctx, regs, set->sig[0]))
goto give_sigsegv;
if (_NSIG_WORDS > 1) {
if (__copy_to_user(frame->extramask, &set->sig[1],
sizeof(frame->extramask)))
goto give_sigsegv;
}
/* set up to return from userspace. If provided, use a stub already in
* userspace */
if (ka->sa.sa_flags & SA_RESTORER) {
if (__put_user(ka->sa.sa_restorer, &frame->pretcode))
goto give_sigsegv;
} else {
if (__put_user((void (*)(void))frame->retcode,
&frame->pretcode))
goto give_sigsegv;
/* this is mov $,d0; syscall 0 */
if (__put_user(0x2c, (char *)(frame->retcode + 0)) ||
__put_user(__NR_sigreturn, (char *)(frame->retcode + 1)) ||
__put_user(0x00, (char *)(frame->retcode + 2)) ||
__put_user(0xf0, (char *)(frame->retcode + 3)) ||
__put_user(0xe0, (char *)(frame->retcode + 4)))
goto give_sigsegv;
flush_icache_range((unsigned long) frame->retcode,
(unsigned long) frame->retcode + 5);
}
/* set up registers for signal handler */
regs->sp = (unsigned long) frame;
regs->pc = (unsigned long) ka->sa.sa_handler;
regs->d0 = sig;
regs->d1 = (unsigned long) &frame->sc;
set_fs(USER_DS);
/* the tracer may want to single-step inside the handler */
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
#if DEBUG_SIG
printk(KERN_DEBUG "SIG deliver %d (%s:%d): sp=%p pc=%lx ra=%p\n",
sig, current->comm, current->pid, frame, regs->pc,
frame->pretcode);
#endif
return 0;
give_sigsegv:
force_sig(SIGSEGV, current);
return -EFAULT;
}
/*
* set up a realtime signal frame
*/
static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs *regs)
{
struct rt_sigframe __user *frame;
int rsig;
frame = get_sigframe(ka, regs, sizeof(*frame));
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto give_sigsegv;
rsig = sig;
if (sig < 32 &&
current_thread_info()->exec_domain &&
current_thread_info()->exec_domain->signal_invmap)
rsig = current_thread_info()->exec_domain->signal_invmap[sig];
if (__put_user(rsig, &frame->sig) ||
__put_user(&frame->info, &frame->pinfo) ||
__put_user(&frame->uc, &frame->puc) ||
copy_siginfo_to_user(&frame->info, info))
goto give_sigsegv;
/* create the ucontext. */
if (__put_user(0, &frame->uc.uc_flags) ||
__put_user(0, &frame->uc.uc_link) ||
__put_user((void *)current->sas_ss_sp, &frame->uc.uc_stack.ss_sp) ||
__put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags) ||
__put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size) ||
setup_sigcontext(&frame->uc.uc_mcontext,
&frame->fpuctx, regs, set->sig[0]) ||
__copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)))
goto give_sigsegv;
/* set up to return from userspace. If provided, use a stub already in
* userspace */
if (ka->sa.sa_flags & SA_RESTORER) {
if (__put_user(ka->sa.sa_restorer, &frame->pretcode))
goto give_sigsegv;
} else {
if (__put_user((void(*)(void))frame->retcode,
&frame->pretcode) ||
/* This is mov $,d0; syscall 0 */
__put_user(0x2c, (char *)(frame->retcode + 0)) ||
__put_user(__NR_rt_sigreturn,
(char *)(frame->retcode + 1)) ||
__put_user(0x00, (char *)(frame->retcode + 2)) ||
__put_user(0xf0, (char *)(frame->retcode + 3)) ||
__put_user(0xe0, (char *)(frame->retcode + 4)))
goto give_sigsegv;
flush_icache_range((u_long) frame->retcode,
(u_long) frame->retcode + 5);
}
/* Set up registers for signal handler */
regs->sp = (unsigned long) frame;
regs->pc = (unsigned long) ka->sa.sa_handler;
regs->d0 = sig;
regs->d1 = (long) &frame->info;
set_fs(USER_DS);
/* the tracer may want to single-step inside the handler */
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
#if DEBUG_SIG
printk(KERN_DEBUG "SIG deliver %d (%s:%d): sp=%p pc=%lx ra=%p\n",
sig, current->comm, current->pid, frame, regs->pc,
frame->pretcode);
#endif
return 0;
give_sigsegv:
force_sig(SIGSEGV, current);
return -EFAULT;
}
/*
* handle the actual delivery of a signal to userspace
*/
static int handle_signal(int sig,
siginfo_t *info, struct k_sigaction *ka,
sigset_t *oldset, struct pt_regs *regs)
{
int ret;
/* Are we from a system call? */
if (regs->orig_d0 >= 0) {
/* If so, check system call restarting.. */
switch (regs->d0) {
case -ERESTART_RESTARTBLOCK:
case -ERESTARTNOHAND:
regs->d0 = -EINTR;
break;
case -ERESTARTSYS:
if (!(ka->sa.sa_flags & SA_RESTART)) {
regs->d0 = -EINTR;
break;
}
/* fallthrough */
case -ERESTARTNOINTR:
regs->d0 = regs->orig_d0;
regs->pc -= 2;
}
}
/* Set up the stack frame */
if (ka->sa.sa_flags & SA_SIGINFO)
ret = setup_rt_frame(sig, ka, info, oldset, regs);
else
ret = setup_frame(sig, ka, oldset, regs);
if (ret == 0) {
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);
}
return ret;
}
/*
* handle a potential signal
*/
static void do_signal(struct pt_regs *regs)
{
struct k_sigaction ka;
siginfo_t info;
sigset_t *oldset;
int signr;
/* we want the common case to go fast, which is why we may in certain
* cases get here from kernel mode */
if (!user_mode(regs))
return;
if (test_thread_flag(TIF_RESTORE_SIGMASK))
oldset = &current->saved_sigmask;
else
oldset = &current->blocked;
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
/* a signal was successfully delivered; the saved
* sigmask will have been stored in the signal frame,
* and will be restored by sigreturn, so we can simply
* clear the TIF_RESTORE_SIGMASK flag */
if (test_thread_flag(TIF_RESTORE_SIGMASK))
clear_thread_flag(TIF_RESTORE_SIGMASK);
tracehook_signal_handler(signr, &info, &ka, regs,
test_thread_flag(TIF_SINGLESTEP));
}
return;
}
/* did we come from a system call? */
if (regs->orig_d0 >= 0) {
/* restart the system call - no handlers present */
switch (regs->d0) {
case -ERESTARTNOHAND:
case -ERESTARTSYS:
case -ERESTARTNOINTR:
regs->d0 = regs->orig_d0;
regs->pc -= 2;
break;
case -ERESTART_RESTARTBLOCK:
regs->d0 = __NR_restart_syscall;
regs->pc -= 2;
break;
}
}
/* if there's no signal to deliver, we just put the saved sigmask
* back */
if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
clear_thread_flag(TIF_RESTORE_SIGMASK);
sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
}
}
/*
* notification of userspace execution resumption
* - triggered by current->work.notify_resume
*/
asmlinkage void do_notify_resume(struct pt_regs *regs, u32 thread_info_flags)
{
/* Pending single-step? */
if (thread_info_flags & _TIF_SINGLESTEP) {
#ifndef CONFIG_MN10300_USING_JTAG
regs->epsw |= EPSW_T;
clear_thread_flag(TIF_SINGLESTEP);
#else
BUG(); /* no h/w single-step if using JTAG unit */
#endif
}
/* deal with pending signal delivery */
if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
do_signal(regs);
if (thread_info_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
tracehook_notify_resume(__frame);
if (current->replacement_session_keyring)
key_replace_session_keyring();
}
}
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