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ee18d64c1f
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>
333 lines
7.4 KiB
C
333 lines
7.4 KiB
C
/*
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* Copyright (C) 2004-2006 Atmel Corporation
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*
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* Based on linux/arch/sh/kernel/signal.c
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* Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/errno.h>
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#include <linux/ptrace.h>
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#include <linux/unistd.h>
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#include <linux/freezer.h>
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#include <asm/uaccess.h>
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#include <asm/ucontext.h>
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#include <asm/syscalls.h>
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#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
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asmlinkage int sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
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struct pt_regs *regs)
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{
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return do_sigaltstack(uss, uoss, regs->sp);
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}
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struct rt_sigframe
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{
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struct siginfo info;
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struct ucontext uc;
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unsigned long retcode;
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};
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static int
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restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
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{
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int err = 0;
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#define COPY(x) err |= __get_user(regs->x, &sc->x)
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COPY(sr);
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COPY(pc);
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COPY(lr);
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COPY(sp);
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COPY(r12);
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COPY(r11);
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COPY(r10);
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COPY(r9);
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COPY(r8);
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COPY(r7);
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COPY(r6);
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COPY(r5);
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COPY(r4);
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COPY(r3);
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COPY(r2);
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COPY(r1);
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COPY(r0);
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#undef COPY
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/*
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* Don't allow anyone to pretend they're running in supervisor
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* mode or something...
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*/
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err |= !valid_user_regs(regs);
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return err;
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}
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asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
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{
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struct rt_sigframe __user *frame;
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sigset_t set;
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frame = (struct rt_sigframe __user *)regs->sp;
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pr_debug("SIG return: frame = %p\n", frame);
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if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
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goto badframe;
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if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
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goto badframe;
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sigdelsetmask(&set, ~_BLOCKABLE);
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spin_lock_irq(¤t->sighand->siglock);
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current->blocked = set;
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recalc_sigpending();
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spin_unlock_irq(¤t->sighand->siglock);
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if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
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goto badframe;
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if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
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goto badframe;
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pr_debug("Context restored: pc = %08lx, lr = %08lx, sp = %08lx\n",
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regs->pc, regs->lr, regs->sp);
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return regs->r12;
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badframe:
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force_sig(SIGSEGV, current);
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return 0;
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}
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static int
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setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
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{
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int err = 0;
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#define COPY(x) err |= __put_user(regs->x, &sc->x)
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COPY(sr);
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COPY(pc);
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COPY(lr);
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COPY(sp);
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COPY(r12);
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COPY(r11);
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COPY(r10);
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COPY(r9);
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COPY(r8);
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COPY(r7);
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COPY(r6);
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COPY(r5);
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COPY(r4);
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COPY(r3);
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COPY(r2);
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COPY(r1);
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COPY(r0);
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#undef COPY
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return err;
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}
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static inline void __user *
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get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, int framesize)
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{
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unsigned long sp = regs->sp;
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if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
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sp = current->sas_ss_sp + current->sas_ss_size;
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return (void __user *)((sp - framesize) & ~3);
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}
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static int
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setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
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sigset_t *set, struct pt_regs *regs)
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{
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struct rt_sigframe __user *frame;
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int err = 0;
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frame = get_sigframe(ka, regs, sizeof(*frame));
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err = -EFAULT;
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if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
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goto out;
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/*
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* Set up the return code:
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*
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* mov r8, __NR_rt_sigreturn
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* scall
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*
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* Note: This will blow up since we're using a non-executable
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* stack. Better use SA_RESTORER.
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*/
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#if __NR_rt_sigreturn > 127
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# error __NR_rt_sigreturn must be < 127 to fit in a short mov
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#endif
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err = __put_user(0x3008d733 | (__NR_rt_sigreturn << 20),
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&frame->retcode);
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err |= copy_siginfo_to_user(&frame->info, info);
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/* Set up the ucontext */
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err |= __put_user(0, &frame->uc.uc_flags);
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err |= __put_user(NULL, &frame->uc.uc_link);
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err |= __put_user((void __user *)current->sas_ss_sp,
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&frame->uc.uc_stack.ss_sp);
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err |= __put_user(sas_ss_flags(regs->sp),
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&frame->uc.uc_stack.ss_flags);
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err |= __put_user(current->sas_ss_size,
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&frame->uc.uc_stack.ss_size);
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err |= setup_sigcontext(&frame->uc.uc_mcontext, regs);
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err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
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if (err)
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goto out;
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regs->r12 = sig;
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regs->r11 = (unsigned long) &frame->info;
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regs->r10 = (unsigned long) &frame->uc;
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regs->sp = (unsigned long) frame;
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if (ka->sa.sa_flags & SA_RESTORER)
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regs->lr = (unsigned long)ka->sa.sa_restorer;
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else {
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printk(KERN_NOTICE "[%s:%d] did not set SA_RESTORER\n",
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current->comm, current->pid);
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regs->lr = (unsigned long) &frame->retcode;
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}
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pr_debug("SIG deliver [%s:%d]: sig=%d sp=0x%lx pc=0x%lx->0x%p lr=0x%lx\n",
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current->comm, current->pid, sig, regs->sp,
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regs->pc, ka->sa.sa_handler, regs->lr);
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regs->pc = (unsigned long) ka->sa.sa_handler;
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out:
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return err;
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}
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static inline void setup_syscall_restart(struct pt_regs *regs)
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{
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if (regs->r12 == -ERESTART_RESTARTBLOCK)
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regs->r8 = __NR_restart_syscall;
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else
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regs->r12 = regs->r12_orig;
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regs->pc -= 2;
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}
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static inline void
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handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
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sigset_t *oldset, struct pt_regs *regs, int syscall)
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{
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int ret;
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/*
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* Set up the stack frame
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*/
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ret = setup_rt_frame(sig, ka, info, oldset, regs);
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/*
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* Check that the resulting registers are sane
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*/
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ret |= !valid_user_regs(regs);
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/*
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* Block the signal if we were unsuccessful.
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*/
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if (ret != 0 || !(ka->sa.sa_flags & SA_NODEFER)) {
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spin_lock_irq(¤t->sighand->siglock);
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sigorsets(¤t->blocked, ¤t->blocked,
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&ka->sa.sa_mask);
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sigaddset(¤t->blocked, sig);
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recalc_sigpending();
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spin_unlock_irq(¤t->sighand->siglock);
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}
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if (ret == 0)
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return;
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force_sigsegv(sig, current);
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}
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/*
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* Note that 'init' is a special process: it doesn't get signals it
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* doesn't want to handle. Thus you cannot kill init even with a
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* SIGKILL even by mistake.
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*/
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int do_signal(struct pt_regs *regs, sigset_t *oldset, int syscall)
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{
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siginfo_t info;
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int signr;
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struct k_sigaction ka;
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/*
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* We want the common case to go fast, which is why we may in
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* certain cases get here from kernel mode. Just return
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* without doing anything if so.
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*/
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if (!user_mode(regs))
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return 0;
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if (test_thread_flag(TIF_RESTORE_SIGMASK))
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oldset = ¤t->saved_sigmask;
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else if (!oldset)
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oldset = ¤t->blocked;
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signr = get_signal_to_deliver(&info, &ka, regs, NULL);
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if (syscall) {
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switch (regs->r12) {
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case -ERESTART_RESTARTBLOCK:
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case -ERESTARTNOHAND:
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if (signr > 0) {
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regs->r12 = -EINTR;
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break;
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}
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/* fall through */
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case -ERESTARTSYS:
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if (signr > 0 && !(ka.sa.sa_flags & SA_RESTART)) {
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regs->r12 = -EINTR;
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break;
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}
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/* fall through */
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case -ERESTARTNOINTR:
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setup_syscall_restart(regs);
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}
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}
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if (signr == 0) {
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/* No signal to deliver -- put the saved sigmask back */
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if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
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clear_thread_flag(TIF_RESTORE_SIGMASK);
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sigprocmask(SIG_SETMASK, ¤t->saved_sigmask, NULL);
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}
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return 0;
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}
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handle_signal(signr, &ka, &info, oldset, regs, syscall);
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return 1;
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}
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asmlinkage void do_notify_resume(struct pt_regs *regs, struct thread_info *ti)
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{
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int syscall = 0;
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if ((sysreg_read(SR) & MODE_MASK) == MODE_SUPERVISOR)
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syscall = 1;
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if (ti->flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
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do_signal(regs, ¤t->blocked, syscall);
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if (ti->flags & _TIF_NOTIFY_RESUME) {
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clear_thread_flag(TIF_NOTIFY_RESUME);
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tracehook_notify_resume(regs);
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if (current->replacement_session_keyring)
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key_replace_session_keyring();
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}
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}
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