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alistair23-linux/include/linux/signal.h
Eric W. Biederman d08477aa97 fcntl: Don't use ambiguous SIG_POLL si_codes 
We have a weird and problematic intersection of features that when
they all come together result in ambiguous siginfo values, that
we can not support properly.

- Supporting fcntl(F_SETSIG,...) with arbitrary valid signals.

- Using positive values for POLL_IN, POLL_OUT, POLL_MSG, ..., etc
  that imply they are signal specific si_codes and using the
  aforementioned arbitrary signal to deliver them.

- Supporting injection of arbitrary siginfo values for debugging and
  checkpoint/restore.

The result is that just looking at siginfo si_codes of 1 to 6 are
ambigious.  It could either be a signal specific si_code or it could
be a generic si_code.

For most of the kernel this is a non-issue but for sending signals
with siginfo it is impossible to play back the kernel signals and
get the same result.

Strictly speaking when the si_code was changed from SI_SIGIO to
POLL_IN and friends between 2.2 and 2.4 this functionality was not
ambiguous, as only real time signals were supported.  Before 2.4 was
released the kernel began supporting siginfo with non realtime signals
so they could give details of why the signal was sent.

The result is that if F_SETSIG is set to one of the signals with signal
specific si_codes then user space can not know why the signal was sent.

I grepped through a bunch of userspace programs using debian code
search to get a feel for how often people choose a signal that results
in an ambiguous si_code.  I only found one program doing so and it was
using SIGCHLD to test the F_SETSIG functionality, and did not appear
to be a real world usage.

Therefore the ambiguity does not appears to be a real world problem in
practice.  Remove the ambiguity while introducing the smallest chance
of breakage by changing the si_code to SI_SIGIO when signals with
signal specific si_codes are targeted.

Fixes: v2.3.40 -- Added support for queueing non-rt signals
Fixes: v2.3.21 -- Changed the si_code from SI_SIGIO
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-07-24 14:29:23 -05:00

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#ifndef _LINUX_SIGNAL_H
#define _LINUX_SIGNAL_H
#include <linux/bug.h>
#include <linux/signal_types.h>
#include <linux/string.h>
struct task_struct;
/* for sysctl */
extern int print_fatal_signals;
static inline void copy_siginfo(struct siginfo *to, struct siginfo *from)
{
if (from->si_code < 0)
memcpy(to, from, sizeof(*to));
else
/* _sigchld is currently the largest know union member */
memcpy(to, from, __ARCH_SI_PREAMBLE_SIZE + sizeof(from->_sifields._sigchld));
}
int copy_siginfo_to_user(struct siginfo __user *to, const struct siginfo *from);
/*
* Define some primitives to manipulate sigset_t.
*/
#ifndef __HAVE_ARCH_SIG_BITOPS
#include <linux/bitops.h>
/* We don't use <linux/bitops.h> for these because there is no need to
be atomic. */
static inline void sigaddset(sigset_t *set, int _sig)
{
unsigned long sig = _sig - 1;
if (_NSIG_WORDS == 1)
set->sig[0] |= 1UL << sig;
else
set->sig[sig / _NSIG_BPW] |= 1UL << (sig % _NSIG_BPW);
}
static inline void sigdelset(sigset_t *set, int _sig)
{
unsigned long sig = _sig - 1;
if (_NSIG_WORDS == 1)
set->sig[0] &= ~(1UL << sig);
else
set->sig[sig / _NSIG_BPW] &= ~(1UL << (sig % _NSIG_BPW));
}
static inline int sigismember(sigset_t *set, int _sig)
{
unsigned long sig = _sig - 1;
if (_NSIG_WORDS == 1)
return 1 & (set->sig[0] >> sig);
else
return 1 & (set->sig[sig / _NSIG_BPW] >> (sig % _NSIG_BPW));
}
#endif /* __HAVE_ARCH_SIG_BITOPS */
static inline int sigisemptyset(sigset_t *set)
{
switch (_NSIG_WORDS) {
case 4:
return (set->sig[3] | set->sig[2] |
set->sig[1] | set->sig[0]) == 0;
case 2:
return (set->sig[1] | set->sig[0]) == 0;
case 1:
return set->sig[0] == 0;
default:
BUILD_BUG();
return 0;
}
}
static inline int sigequalsets(const sigset_t *set1, const sigset_t *set2)
{
switch (_NSIG_WORDS) {
case 4:
return (set1->sig[3] == set2->sig[3]) &&
(set1->sig[2] == set2->sig[2]) &&
(set1->sig[1] == set2->sig[1]) &&
(set1->sig[0] == set2->sig[0]);
case 2:
return (set1->sig[1] == set2->sig[1]) &&
(set1->sig[0] == set2->sig[0]);
case 1:
return set1->sig[0] == set2->sig[0];
}
return 0;
}
#define sigmask(sig) (1UL << ((sig) - 1))
#ifndef __HAVE_ARCH_SIG_SETOPS
#include <linux/string.h>
#define _SIG_SET_BINOP(name, op) \
static inline void name(sigset_t *r, const sigset_t *a, const sigset_t *b) \
{ \
unsigned long a0, a1, a2, a3, b0, b1, b2, b3; \
\
switch (_NSIG_WORDS) { \
case 4: \
a3 = a->sig[3]; a2 = a->sig[2]; \
b3 = b->sig[3]; b2 = b->sig[2]; \
r->sig[3] = op(a3, b3); \
r->sig[2] = op(a2, b2); \
case 2: \
a1 = a->sig[1]; b1 = b->sig[1]; \
r->sig[1] = op(a1, b1); \
case 1: \
a0 = a->sig[0]; b0 = b->sig[0]; \
r->sig[0] = op(a0, b0); \
break; \
default: \
BUILD_BUG(); \
} \
}
#define _sig_or(x,y) ((x) | (y))
_SIG_SET_BINOP(sigorsets, _sig_or)
#define _sig_and(x,y) ((x) & (y))
_SIG_SET_BINOP(sigandsets, _sig_and)
#define _sig_andn(x,y) ((x) & ~(y))
_SIG_SET_BINOP(sigandnsets, _sig_andn)
#undef _SIG_SET_BINOP
#undef _sig_or
#undef _sig_and
#undef _sig_andn
#define _SIG_SET_OP(name, op) \
static inline void name(sigset_t *set) \
{ \
switch (_NSIG_WORDS) { \
case 4: set->sig[3] = op(set->sig[3]); \
set->sig[2] = op(set->sig[2]); \
case 2: set->sig[1] = op(set->sig[1]); \
case 1: set->sig[0] = op(set->sig[0]); \
break; \
default: \
BUILD_BUG(); \
} \
}
#define _sig_not(x) (~(x))
_SIG_SET_OP(signotset, _sig_not)
#undef _SIG_SET_OP
#undef _sig_not
static inline void sigemptyset(sigset_t *set)
{
switch (_NSIG_WORDS) {
default:
memset(set, 0, sizeof(sigset_t));
break;
case 2: set->sig[1] = 0;
case 1: set->sig[0] = 0;
break;
}
}
static inline void sigfillset(sigset_t *set)
{
switch (_NSIG_WORDS) {
default:
memset(set, -1, sizeof(sigset_t));
break;
case 2: set->sig[1] = -1;
case 1: set->sig[0] = -1;
break;
}
}
/* Some extensions for manipulating the low 32 signals in particular. */
static inline void sigaddsetmask(sigset_t *set, unsigned long mask)
{
set->sig[0] |= mask;
}
static inline void sigdelsetmask(sigset_t *set, unsigned long mask)
{
set->sig[0] &= ~mask;
}
static inline int sigtestsetmask(sigset_t *set, unsigned long mask)
{
return (set->sig[0] & mask) != 0;
}
static inline void siginitset(sigset_t *set, unsigned long mask)
{
set->sig[0] = mask;
switch (_NSIG_WORDS) {
default:
memset(&set->sig[1], 0, sizeof(long)*(_NSIG_WORDS-1));
break;
case 2: set->sig[1] = 0;
case 1: ;
}
}
static inline void siginitsetinv(sigset_t *set, unsigned long mask)
{
set->sig[0] = ~mask;
switch (_NSIG_WORDS) {
default:
memset(&set->sig[1], -1, sizeof(long)*(_NSIG_WORDS-1));
break;
case 2: set->sig[1] = -1;
case 1: ;
}
}
#endif /* __HAVE_ARCH_SIG_SETOPS */
static inline void init_sigpending(struct sigpending *sig)
{
sigemptyset(&sig->signal);
INIT_LIST_HEAD(&sig->list);
}
extern void flush_sigqueue(struct sigpending *queue);
/* Test if 'sig' is valid signal. Use this instead of testing _NSIG directly */
static inline int valid_signal(unsigned long sig)
{
return sig <= _NSIG ? 1 : 0;
}
struct timespec;
struct pt_regs;
extern int next_signal(struct sigpending *pending, sigset_t *mask);
extern int do_send_sig_info(int sig, struct siginfo *info,
struct task_struct *p, bool group);
extern int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p);
extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *);
extern int sigprocmask(int, sigset_t *, sigset_t *);
extern void set_current_blocked(sigset_t *);
extern void __set_current_blocked(const sigset_t *);
extern int show_unhandled_signals;
extern int get_signal(struct ksignal *ksig);
extern void signal_setup_done(int failed, struct ksignal *ksig, int stepping);
extern void exit_signals(struct task_struct *tsk);
extern void kernel_sigaction(int, __sighandler_t);
static inline void allow_signal(int sig)
{
/*
* Kernel threads handle their own signals. Let the signal code
* know it'll be handled, so that they don't get converted to
* SIGKILL or just silently dropped.
*/
kernel_sigaction(sig, (__force __sighandler_t)2);
}
static inline void disallow_signal(int sig)
{
kernel_sigaction(sig, SIG_IGN);
}
extern struct kmem_cache *sighand_cachep;
int unhandled_signal(struct task_struct *tsk, int sig);
/*
* In POSIX a signal is sent either to a specific thread (Linux task)
* or to the process as a whole (Linux thread group). How the signal
* is sent determines whether it's to one thread or the whole group,
* which determines which signal mask(s) are involved in blocking it
* from being delivered until later. When the signal is delivered,
* either it's caught or ignored by a user handler or it has a default
* effect that applies to the whole thread group (POSIX process).
*
* The possible effects an unblocked signal set to SIG_DFL can have are:
* ignore - Nothing Happens
* terminate - kill the process, i.e. all threads in the group,
* similar to exit_group. The group leader (only) reports
* WIFSIGNALED status to its parent.
* coredump - write a core dump file describing all threads using
* the same mm and then kill all those threads
* stop - stop all the threads in the group, i.e. TASK_STOPPED state
*
* SIGKILL and SIGSTOP cannot be caught, blocked, or ignored.
* Other signals when not blocked and set to SIG_DFL behaves as follows.
* The job control signals also have other special effects.
*
* +--------------------+------------------+
* | POSIX signal | default action |
* +--------------------+------------------+
* | SIGHUP | terminate |
* | SIGINT | terminate |
* | SIGQUIT | coredump |
* | SIGILL | coredump |
* | SIGTRAP | coredump |
* | SIGABRT/SIGIOT | coredump |
* | SIGBUS | coredump |
* | SIGFPE | coredump |
* | SIGKILL | terminate(+) |
* | SIGUSR1 | terminate |
* | SIGSEGV | coredump |
* | SIGUSR2 | terminate |
* | SIGPIPE | terminate |
* | SIGALRM | terminate |
* | SIGTERM | terminate |
* | SIGCHLD | ignore |
* | SIGCONT | ignore(*) |
* | SIGSTOP | stop(*)(+) |
* | SIGTSTP | stop(*) |
* | SIGTTIN | stop(*) |
* | SIGTTOU | stop(*) |
* | SIGURG | ignore |
* | SIGXCPU | coredump |
* | SIGXFSZ | coredump |
* | SIGVTALRM | terminate |
* | SIGPROF | terminate |
* | SIGPOLL/SIGIO | terminate |
* | SIGSYS/SIGUNUSED | coredump |
* | SIGSTKFLT | terminate |
* | SIGWINCH | ignore |
* | SIGPWR | terminate |
* | SIGRTMIN-SIGRTMAX | terminate |
* +--------------------+------------------+
* | non-POSIX signal | default action |
* +--------------------+------------------+
* | SIGEMT | coredump |
* +--------------------+------------------+
*
* (+) For SIGKILL and SIGSTOP the action is "always", not just "default".
* (*) Special job control effects:
* When SIGCONT is sent, it resumes the process (all threads in the group)
* from TASK_STOPPED state and also clears any pending/queued stop signals
* (any of those marked with "stop(*)"). This happens regardless of blocking,
* catching, or ignoring SIGCONT. When any stop signal is sent, it clears
* any pending/queued SIGCONT signals; this happens regardless of blocking,
* catching, or ignored the stop signal, though (except for SIGSTOP) the
* default action of stopping the process may happen later or never.
*/
#ifdef SIGEMT
#define SIGEMT_MASK rt_sigmask(SIGEMT)
#else
#define SIGEMT_MASK 0
#endif
#if SIGRTMIN > BITS_PER_LONG
#define rt_sigmask(sig) (1ULL << ((sig)-1))
#else
#define rt_sigmask(sig) sigmask(sig)
#endif
#define siginmask(sig, mask) \
((sig) < SIGRTMIN && (rt_sigmask(sig) & (mask)))
#define SIG_KERNEL_ONLY_MASK (\
rt_sigmask(SIGKILL) | rt_sigmask(SIGSTOP))
#define SIG_KERNEL_STOP_MASK (\
rt_sigmask(SIGSTOP) | rt_sigmask(SIGTSTP) | \
rt_sigmask(SIGTTIN) | rt_sigmask(SIGTTOU) )
#define SIG_KERNEL_COREDUMP_MASK (\
rt_sigmask(SIGQUIT) | rt_sigmask(SIGILL) | \
rt_sigmask(SIGTRAP) | rt_sigmask(SIGABRT) | \
rt_sigmask(SIGFPE) | rt_sigmask(SIGSEGV) | \
rt_sigmask(SIGBUS) | rt_sigmask(SIGSYS) | \
rt_sigmask(SIGXCPU) | rt_sigmask(SIGXFSZ) | \
SIGEMT_MASK )
#define SIG_KERNEL_IGNORE_MASK (\
rt_sigmask(SIGCONT) | rt_sigmask(SIGCHLD) | \
rt_sigmask(SIGWINCH) | rt_sigmask(SIGURG) )
#define SIG_SPECIFIC_SICODES_MASK (\
rt_sigmask(SIGILL) | rt_sigmask(SIGFPE) | \
rt_sigmask(SIGSEGV) | rt_sigmask(SIGBUS) | \
rt_sigmask(SIGTRAP) | rt_sigmask(SIGCHLD) | \
rt_sigmask(SIGPOLL) | rt_sigmask(SIGSYS) | \
SIGEMT_MASK )
#define sig_kernel_only(sig) siginmask(sig, SIG_KERNEL_ONLY_MASK)
#define sig_kernel_coredump(sig) siginmask(sig, SIG_KERNEL_COREDUMP_MASK)
#define sig_kernel_ignore(sig) siginmask(sig, SIG_KERNEL_IGNORE_MASK)
#define sig_kernel_stop(sig) siginmask(sig, SIG_KERNEL_STOP_MASK)
#define sig_specific_sicodes(sig) siginmask(sig, SIG_SPECIFIC_SICODES_MASK)
#define sig_fatal(t, signr) \
(!siginmask(signr, SIG_KERNEL_IGNORE_MASK|SIG_KERNEL_STOP_MASK) && \
(t)->sighand->action[(signr)-1].sa.sa_handler == SIG_DFL)
void signals_init(void);
int restore_altstack(const stack_t __user *);
int __save_altstack(stack_t __user *, unsigned long);
#define save_altstack_ex(uss, sp) do { \
stack_t __user *__uss = uss; \
struct task_struct *t = current; \
put_user_ex((void __user *)t->sas_ss_sp, &__uss->ss_sp); \
put_user_ex(t->sas_ss_flags, &__uss->ss_flags); \
put_user_ex(t->sas_ss_size, &__uss->ss_size); \
if (t->sas_ss_flags & SS_AUTODISARM) \
sas_ss_reset(t); \
} while (0);
#ifdef CONFIG_PROC_FS
struct seq_file;
extern void render_sigset_t(struct seq_file *, const char *, sigset_t *);
#endif
#endif /* _LINUX_SIGNAL_H */
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