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20b40a794b
linux_dsm_epyc7002/arch/s390/kernel/compat_signal.c
Martin Schwidefsky 20b40a794b [S390] signal race with restarting system calls 
For a ERESTARTNOHAND/ERESTARTSYS/ERESTARTNOINTR restarting system call
do_signal will prepare the restart of the system call with a rewind of
the PSW before calling get_signal_to_deliver (where the debugger might
take control). For A ERESTART_RESTARTBLOCK restarting system call
do_signal will set -EINTR as return code.
There are two issues with this approach:
1) strace never sees ERESTARTNOHAND, ERESTARTSYS, ERESTARTNOINTR or
   ERESTART_RESTARTBLOCK as the rewinding already took place or the
   return code has been changed to -EINTR
2) if get_signal_to_deliver does not return with a signal to deliver
   the restart via the repeat of the svc instruction is left in place.
   This opens a race if another signal is made pending before the
   system call instruction can be reexecuted. The original system call
   will be restarted even if the second signal would have ended the
   system call with -EINTR.

These two issues can be solved by dropping the early rewind of the
system call before get_signal_to_deliver has been called and by using
the TIF_RESTART_SVC magic to do the restart if no signal has to be
delivered. The only situation where the system call restart via the
repeat of the svc instruction is appropriate is when a SA_RESTART
signal is delivered to user space.

Unfortunately this breaks inferior calls by the debugger again. The
system call number and the length of the system call instruction is
lost over the inferior call and user space will see ERESTARTNOHAND/
ERESTARTSYS/ERESTARTNOINTR/ERESTART_RESTARTBLOCK. To correct this a
new ptrace interface is added to save/restore the system call number
and system call instruction length.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-10-30 15:16:43 +01:00

612 lines
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/*
* arch/s390/kernel/compat_signal.c
*
* Copyright (C) IBM Corp. 2000,2006
* Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
* Gerhard Tonn (ton@de.ibm.com)
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
*/
#include <linux/compat.h>
#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/binfmts.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/lowcore.h>
#include "compat_linux.h"
#include "compat_ptrace.h"
#include "entry.h"
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
typedef struct
{
__u8 callee_used_stack[__SIGNAL_FRAMESIZE32];
struct sigcontext32 sc;
_sigregs32 sregs;
int signo;
__u32 gprs_high[NUM_GPRS];
__u8 retcode[S390_SYSCALL_SIZE];
} sigframe32;
typedef struct
{
__u8 callee_used_stack[__SIGNAL_FRAMESIZE32];
__u8 retcode[S390_SYSCALL_SIZE];
compat_siginfo_t info;
struct ucontext32 uc;
__u32 gprs_high[NUM_GPRS];
} rt_sigframe32;
int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
{
int err;
if (!access_ok (VERIFY_WRITE, to, sizeof(compat_siginfo_t)))
return -EFAULT;
/* If you change siginfo_t structure, please be sure
this code is fixed accordingly.
It should never copy any pad contained in the structure
to avoid security leaks, but must copy the generic
3 ints plus the relevant union member.
This routine must convert siginfo from 64bit to 32bit as well
at the same time. */
err = __put_user(from->si_signo, &to->si_signo);
err |= __put_user(from->si_errno, &to->si_errno);
err |= __put_user((short)from->si_code, &to->si_code);
if (from->si_code < 0)
err |= __copy_to_user(&to->_sifields._pad, &from->_sifields._pad, SI_PAD_SIZE);
else {
switch (from->si_code >> 16) {
case __SI_RT >> 16: /* This is not generated by the kernel as of now. */
case __SI_MESGQ >> 16:
err |= __put_user(from->si_int, &to->si_int);
/* fallthrough */
case __SI_KILL >> 16:
err |= __put_user(from->si_pid, &to->si_pid);
err |= __put_user(from->si_uid, &to->si_uid);
break;
case __SI_CHLD >> 16:
err |= __put_user(from->si_pid, &to->si_pid);
err |= __put_user(from->si_uid, &to->si_uid);
err |= __put_user(from->si_utime, &to->si_utime);
err |= __put_user(from->si_stime, &to->si_stime);
err |= __put_user(from->si_status, &to->si_status);
break;
case __SI_FAULT >> 16:
err |= __put_user((unsigned long) from->si_addr,
&to->si_addr);
break;
case __SI_POLL >> 16:
err |= __put_user(from->si_band, &to->si_band);
err |= __put_user(from->si_fd, &to->si_fd);
break;
case __SI_TIMER >> 16:
err |= __put_user(from->si_tid, &to->si_tid);
err |= __put_user(from->si_overrun, &to->si_overrun);
err |= __put_user(from->si_int, &to->si_int);
break;
default:
break;
}
}
return err;
}
int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
{
int err;
u32 tmp;
if (!access_ok (VERIFY_READ, from, sizeof(compat_siginfo_t)))
return -EFAULT;
err = __get_user(to->si_signo, &from->si_signo);
err |= __get_user(to->si_errno, &from->si_errno);
err |= __get_user(to->si_code, &from->si_code);
if (to->si_code < 0)
err |= __copy_from_user(&to->_sifields._pad, &from->_sifields._pad, SI_PAD_SIZE);
else {
switch (to->si_code >> 16) {
case __SI_RT >> 16: /* This is not generated by the kernel as of now. */
case __SI_MESGQ >> 16:
err |= __get_user(to->si_int, &from->si_int);
/* fallthrough */
case __SI_KILL >> 16:
err |= __get_user(to->si_pid, &from->si_pid);
err |= __get_user(to->si_uid, &from->si_uid);
break;
case __SI_CHLD >> 16:
err |= __get_user(to->si_pid, &from->si_pid);
err |= __get_user(to->si_uid, &from->si_uid);
err |= __get_user(to->si_utime, &from->si_utime);
err |= __get_user(to->si_stime, &from->si_stime);
err |= __get_user(to->si_status, &from->si_status);
break;
case __SI_FAULT >> 16:
err |= __get_user(tmp, &from->si_addr);
to->si_addr = (void __user *)(u64) (tmp & PSW32_ADDR_INSN);
break;
case __SI_POLL >> 16:
err |= __get_user(to->si_band, &from->si_band);
err |= __get_user(to->si_fd, &from->si_fd);
break;
case __SI_TIMER >> 16:
err |= __get_user(to->si_tid, &from->si_tid);
err |= __get_user(to->si_overrun, &from->si_overrun);
err |= __get_user(to->si_int, &from->si_int);
break;
default:
break;
}
}
return err;
}
asmlinkage long
sys32_sigaction(int sig, const struct old_sigaction32 __user *act,
struct old_sigaction32 __user *oact)
{
struct k_sigaction new_ka, old_ka;
unsigned long sa_handler, sa_restorer;
int ret;
if (act) {
compat_old_sigset_t mask;
if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
__get_user(sa_handler, &act->sa_handler) ||
__get_user(sa_restorer, &act->sa_restorer) ||
__get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
__get_user(mask, &act->sa_mask))
return -EFAULT;
new_ka.sa.sa_handler = (__sighandler_t) sa_handler;
new_ka.sa.sa_restorer = (void (*)(void)) sa_restorer;
siginitset(&new_ka.sa.sa_mask, mask);
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
sa_handler = (unsigned long) old_ka.sa.sa_handler;
sa_restorer = (unsigned long) old_ka.sa.sa_restorer;
if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
__put_user(sa_handler, &oact->sa_handler) ||
__put_user(sa_restorer, &oact->sa_restorer) ||
__put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
return -EFAULT;
}
return ret;
}
asmlinkage long
sys32_rt_sigaction(int sig, const struct sigaction32 __user *act,
struct sigaction32 __user *oact, size_t sigsetsize)
{
struct k_sigaction new_ka, old_ka;
unsigned long sa_handler;
int ret;
compat_sigset_t set32;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(compat_sigset_t))
return -EINVAL;
if (act) {
ret = get_user(sa_handler, &act->sa_handler);
ret |= __copy_from_user(&set32, &act->sa_mask,
sizeof(compat_sigset_t));
switch (_NSIG_WORDS) {
case 4: new_ka.sa.sa_mask.sig[3] = set32.sig[6]
| (((long)set32.sig[7]) << 32);
case 3: new_ka.sa.sa_mask.sig[2] = set32.sig[4]
| (((long)set32.sig[5]) << 32);
case 2: new_ka.sa.sa_mask.sig[1] = set32.sig[2]
| (((long)set32.sig[3]) << 32);
case 1: new_ka.sa.sa_mask.sig[0] = set32.sig[0]
| (((long)set32.sig[1]) << 32);
}
ret |= __get_user(new_ka.sa.sa_flags, &act->sa_flags);
if (ret)
return -EFAULT;
new_ka.sa.sa_handler = (__sighandler_t) sa_handler;
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
switch (_NSIG_WORDS) {
case 4:
set32.sig[7] = (old_ka.sa.sa_mask.sig[3] >> 32);
set32.sig[6] = old_ka.sa.sa_mask.sig[3];
case 3:
set32.sig[5] = (old_ka.sa.sa_mask.sig[2] >> 32);
set32.sig[4] = old_ka.sa.sa_mask.sig[2];
case 2:
set32.sig[3] = (old_ka.sa.sa_mask.sig[1] >> 32);
set32.sig[2] = old_ka.sa.sa_mask.sig[1];
case 1:
set32.sig[1] = (old_ka.sa.sa_mask.sig[0] >> 32);
set32.sig[0] = old_ka.sa.sa_mask.sig[0];
}
ret = put_user((unsigned long)old_ka.sa.sa_handler, &oact->sa_handler);
ret |= __copy_to_user(&oact->sa_mask, &set32,
sizeof(compat_sigset_t));
ret |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
}
return ret;
}
asmlinkage long
sys32_sigaltstack(const stack_t32 __user *uss, stack_t32 __user *uoss)
{
struct pt_regs *regs = task_pt_regs(current);
stack_t kss, koss;
unsigned long ss_sp;
int ret, err = 0;
mm_segment_t old_fs = get_fs();
if (uss) {
if (!access_ok(VERIFY_READ, uss, sizeof(*uss)))
return -EFAULT;
err |= __get_user(ss_sp, &uss->ss_sp);
err |= __get_user(kss.ss_size, &uss->ss_size);
err |= __get_user(kss.ss_flags, &uss->ss_flags);
if (err)
return -EFAULT;
kss.ss_sp = (void __user *) ss_sp;
}
set_fs (KERNEL_DS);
ret = do_sigaltstack((stack_t __force __user *) (uss ? &kss : NULL),
(stack_t __force __user *) (uoss ? &koss : NULL),
regs->gprs[15]);
set_fs (old_fs);
if (!ret && uoss) {
if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss)))
return -EFAULT;
ss_sp = (unsigned long) koss.ss_sp;
err |= __put_user(ss_sp, &uoss->ss_sp);
err |= __put_user(koss.ss_size, &uoss->ss_size);
err |= __put_user(koss.ss_flags, &uoss->ss_flags);
if (err)
return -EFAULT;
}
return ret;
}
static int save_sigregs32(struct pt_regs *regs, _sigregs32 __user *sregs)
{
_s390_regs_common32 regs32;
int err, i;
regs32.psw.mask = PSW32_MASK_MERGE(psw32_user_bits,
(__u32)(regs->psw.mask >> 32));
regs32.psw.addr = PSW32_ADDR_AMODE31 | (__u32) regs->psw.addr;
for (i = 0; i < NUM_GPRS; i++)
regs32.gprs[i] = (__u32) regs->gprs[i];
save_access_regs(current->thread.acrs);
memcpy(regs32.acrs, current->thread.acrs, sizeof(regs32.acrs));
err = __copy_to_user(&sregs->regs, &regs32, sizeof(regs32));
if (err)
return err;
save_fp_regs(&current->thread.fp_regs);
/* s390_fp_regs and _s390_fp_regs32 are the same ! */
return __copy_to_user(&sregs->fpregs, &current->thread.fp_regs,
sizeof(_s390_fp_regs32));
}
static int restore_sigregs32(struct pt_regs *regs,_sigregs32 __user *sregs)
{
_s390_regs_common32 regs32;
int err, i;
/* Alwys make any pending restarted system call return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
err = __copy_from_user(&regs32, &sregs->regs, sizeof(regs32));
if (err)
return err;
regs->psw.mask = PSW_MASK_MERGE(regs->psw.mask,
(__u64)regs32.psw.mask << 32);
regs->psw.addr = (__u64)(regs32.psw.addr & PSW32_ADDR_INSN);
for (i = 0; i < NUM_GPRS; i++)
regs->gprs[i] = (__u64) regs32.gprs[i];
memcpy(current->thread.acrs, regs32.acrs, sizeof(current->thread.acrs));
restore_access_regs(current->thread.acrs);
err = __copy_from_user(&current->thread.fp_regs, &sregs->fpregs,
sizeof(_s390_fp_regs32));
current->thread.fp_regs.fpc &= FPC_VALID_MASK;
if (err)
return err;
restore_fp_regs(&current->thread.fp_regs);
regs->svc_code = 0; /* disable syscall checks */
return 0;
}
static int save_sigregs_gprs_high(struct pt_regs *regs, __u32 __user *uregs)
{
__u32 gprs_high[NUM_GPRS];
int i;
for (i = 0; i < NUM_GPRS; i++)
gprs_high[i] = regs->gprs[i] >> 32;
return __copy_to_user(uregs, &gprs_high, sizeof(gprs_high));
}
static int restore_sigregs_gprs_high(struct pt_regs *regs, __u32 __user *uregs)
{
__u32 gprs_high[NUM_GPRS];
int err, i;
err = __copy_from_user(&gprs_high, uregs, sizeof(gprs_high));
if (err)
return err;
for (i = 0; i < NUM_GPRS; i++)
*(__u32 *)&regs->gprs[i] = gprs_high[i];
return 0;
}
asmlinkage long sys32_sigreturn(void)
{
struct pt_regs *regs = task_pt_regs(current);
sigframe32 __user *frame = (sigframe32 __user *)regs->gprs[15];
sigset_t set;
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE32))
goto badframe;
sigdelsetmask(&set, ~_BLOCKABLE);
set_current_blocked(&set);
if (restore_sigregs32(regs, &frame->sregs))
goto badframe;
if (restore_sigregs_gprs_high(regs, frame->gprs_high))
goto badframe;
return regs->gprs[2];
badframe:
force_sig(SIGSEGV, current);
return 0;
}
asmlinkage long sys32_rt_sigreturn(void)
{
struct pt_regs *regs = task_pt_regs(current);
rt_sigframe32 __user *frame = (rt_sigframe32 __user *)regs->gprs[15];
sigset_t set;
stack_t st;
__u32 ss_sp;
int err;
mm_segment_t old_fs = get_fs();
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);
set_current_blocked(&set);
if (restore_sigregs32(regs, &frame->uc.uc_mcontext))
goto badframe;
if (restore_sigregs_gprs_high(regs, frame->gprs_high))
goto badframe;
err = __get_user(ss_sp, &frame->uc.uc_stack.ss_sp);
st.ss_sp = compat_ptr(ss_sp);
err |= __get_user(st.ss_size, &frame->uc.uc_stack.ss_size);
err |= __get_user(st.ss_flags, &frame->uc.uc_stack.ss_flags);
if (err)
goto badframe;
set_fs (KERNEL_DS);
do_sigaltstack((stack_t __force __user *)&st, NULL, regs->gprs[15]);
set_fs (old_fs);
return regs->gprs[2];
badframe:
force_sig(SIGSEGV, current);
return 0;
}
/*
* Set up a signal frame.
*/
/*
* 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 = (unsigned long) A(regs->gprs[15]);
/* Overflow on alternate signal stack gives SIGSEGV. */
if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
return (void __user *) -1UL;
/* This is the X/Open sanctioned signal stack switching. */
if (ka->sa.sa_flags & SA_ONSTACK) {
if (! sas_ss_flags(sp))
sp = current->sas_ss_sp + current->sas_ss_size;
}
/* This is the legacy signal stack switching. */
else if (!user_mode(regs) &&
!(ka->sa.sa_flags & SA_RESTORER) &&
ka->sa.sa_restorer) {
sp = (unsigned long) ka->sa.sa_restorer;
}
return (void __user *)((sp - frame_size) & -8ul);
}
static inline int map_signal(int sig)
{
if (current_thread_info()->exec_domain
&& current_thread_info()->exec_domain->signal_invmap
&& sig < 32)
return current_thread_info()->exec_domain->signal_invmap[sig];
else
return sig;
}
static int setup_frame32(int sig, struct k_sigaction *ka,
sigset_t *set, struct pt_regs * regs)
{
sigframe32 __user *frame = get_sigframe(ka, regs, sizeof(sigframe32));
if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe32)))
goto give_sigsegv;
if (frame == (void __user *) -1UL)
goto give_sigsegv;
if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE32))
goto give_sigsegv;
if (save_sigregs32(regs, &frame->sregs))
goto give_sigsegv;
if (save_sigregs_gprs_high(regs, frame->gprs_high))
goto give_sigsegv;
if (__put_user((unsigned long) &frame->sregs, &frame->sc.sregs))
goto give_sigsegv;
/* Set up to return from userspace. If provided, use a stub
already in userspace. */
if (ka->sa.sa_flags & SA_RESTORER) {
regs->gprs[14] = (__u64) ka->sa.sa_restorer;
} else {
regs->gprs[14] = (__u64) frame->retcode;
if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn,
(u16 __user *)(frame->retcode)))
goto give_sigsegv;
}
/* Set up backchain. */
if (__put_user(regs->gprs[15], (unsigned int __user *) frame))
goto give_sigsegv;
/* Set up registers for signal handler */
regs->gprs[15] = (__u64) frame;
regs->psw.addr = (__u64) ka->sa.sa_handler;
regs->gprs[2] = map_signal(sig);
regs->gprs[3] = (__u64) &frame->sc;
/* We forgot to include these in the sigcontext.
To avoid breaking binary compatibility, they are passed as args. */
regs->gprs[4] = current->thread.trap_no;
regs->gprs[5] = current->thread.prot_addr;
/* Place signal number on stack to allow backtrace from handler. */
if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
goto give_sigsegv;
return 0;
give_sigsegv:
force_sigsegv(sig, current);
return -EFAULT;
}
static int setup_rt_frame32(int sig, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs * regs)
{
int err = 0;
rt_sigframe32 __user *frame = get_sigframe(ka, regs, sizeof(rt_sigframe32));
if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe32)))
goto give_sigsegv;
if (frame == (void __user *) -1UL)
goto give_sigsegv;
if (copy_siginfo_to_user32(&frame->info, info))
goto give_sigsegv;
/* Create the ucontext. */
err |= __put_user(UC_EXTENDED, &frame->uc.uc_flags);
err |= __put_user(0, &frame->uc.uc_link);
err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
err |= __put_user(sas_ss_flags(regs->gprs[15]),
&frame->uc.uc_stack.ss_flags);
err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
err |= save_sigregs32(regs, &frame->uc.uc_mcontext);
err |= save_sigregs_gprs_high(regs, frame->gprs_high);
err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
if (err)
goto give_sigsegv;
/* Set up to return from userspace. If provided, use a stub
already in userspace. */
if (ka->sa.sa_flags & SA_RESTORER) {
regs->gprs[14] = (__u64) ka->sa.sa_restorer;
} else {
regs->gprs[14] = (__u64) frame->retcode;
err |= __put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn,
(u16 __user *)(frame->retcode));
}
/* Set up backchain. */
if (__put_user(regs->gprs[15], (unsigned int __user *) frame))
goto give_sigsegv;
/* Set up registers for signal handler */
regs->gprs[15] = (__u64) frame;
regs->psw.addr = (__u64) ka->sa.sa_handler;
regs->gprs[2] = map_signal(sig);
regs->gprs[3] = (__u64) &frame->info;
regs->gprs[4] = (__u64) &frame->uc;
return 0;
give_sigsegv:
force_sigsegv(sig, current);
return -EFAULT;
}
/*
* OK, we're invoking a handler
*/
int handle_signal32(unsigned long sig, struct k_sigaction *ka,
siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
{
sigset_t blocked;
int ret;
/* Set up the stack frame */
if (ka->sa.sa_flags & SA_SIGINFO)
ret = setup_rt_frame32(sig, ka, info, oldset, regs);
else
ret = setup_frame32(sig, ka, oldset, regs);
if (ret)
return ret;
sigorsets(&blocked, &current->blocked, &ka->sa.sa_mask);
if (!(ka->sa.sa_flags & SA_NODEFER))
sigaddset(&blocked, sig);
set_current_blocked(&blocked);
return 0;
}
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