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signal: Pass pid and pid type into send_sigqueue 

Make the code more maintainable by performing more of the signal
related work in send_sigqueue.

A quick inspection of do_timer_create will show that this code path
does not lookup a thread group by a thread's pid.  Making it safe
to find the task pointed to by it_pid with "pid_task(it_pid, type)";

This supports the changes needed in fork to tell if a signal was sent
to a single process or a group of processes.

Having the pid to task transition in signal.c will also make it easier
to sort out races with de_thread and and the thread group leader
exiting when it comes time to address that.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2018-07-20 14:30:23 -05:00
parent 2118e1f53f
commit 24122c7f49
3 changed files with 14 additions and 15 deletions
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2
include/linux/sched/signal.h
View File

@ -330,7 +330,7 @@ extern int send_sig(int, struct task_struct *, int);
extern int zap_other_threads(struct task_struct *p); extern int zap_other_threads(struct task_struct *p);
extern struct sigqueue *sigqueue_alloc(void); extern struct sigqueue *sigqueue_alloc(void);
extern void sigqueue_free(struct sigqueue *); extern void sigqueue_free(struct sigqueue *);
extern int send_sigqueue(struct sigqueue *, struct task_struct *, int group); extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *); extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
static inline int restart_syscall(void) static inline int restart_syscall(void)

14
kernel/signal.c
View File

@ -1664,17 +1664,20 @@ void sigqueue_free(struct sigqueue *q)
__sigqueue_free(q); __sigqueue_free(q);
} }
int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group) int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
{ {
int sig = q->info.si_signo; int sig = q->info.si_signo;
struct sigpending *pending; struct sigpending *pending;
struct task_struct *t;
unsigned long flags; unsigned long flags;
int ret, result; int ret, result;
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
ret = -1; ret = -1;
if (!likely(lock_task_sighand(t, &flags))) rcu_read_lock();
t = pid_task(pid, type);
if (!t || !likely(lock_task_sighand(t, &flags)))
goto ret; goto ret;
ret = 1; /* the signal is ignored */ ret = 1; /* the signal is ignored */
@ -1696,15 +1699,16 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
q->info.si_overrun = 0; q->info.si_overrun = 0;
signalfd_notify(t, sig); signalfd_notify(t, sig);
pending = group ? &t->signal->shared_pending : &t->pending; pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;
list_add_tail(&q->list, &pending->list); list_add_tail(&q->list, &pending->list);
sigaddset(&pending->signal, sig); sigaddset(&pending->signal, sig);
complete_signal(sig, t, group); complete_signal(sig, t, type != PIDTYPE_PID);
result = TRACE_SIGNAL_DELIVERED; result = TRACE_SIGNAL_DELIVERED;
out: out:
trace_signal_generate(sig, &q->info, t, group, result); trace_signal_generate(sig, &q->info, t, type != PIDTYPE_PID, result);
unlock_task_sighand(t, &flags); unlock_task_sighand(t, &flags);
ret: ret:
rcu_read_unlock();
return ret; return ret;
} }

13
kernel/time/posix-timers.c
View File

@ -332,8 +332,8 @@ void posixtimer_rearm(struct siginfo *info)
int posix_timer_event(struct k_itimer *timr, int si_private) int posix_timer_event(struct k_itimer *timr, int si_private)
{ {
struct task_struct *task; enum pid_type type;
int shared, ret = -1; int ret = -1;
/* /*
* FIXME: if ->sigq is queued we can race with * FIXME: if ->sigq is queued we can race with
* dequeue_signal()->posixtimer_rearm(). * dequeue_signal()->posixtimer_rearm().
@ -347,13 +347,8 @@ int posix_timer_event(struct k_itimer *timr, int si_private)
*/ */
timr->sigq->info.si_sys_private = si_private; timr->sigq->info.si_sys_private = si_private;
rcu_read_lock(); type = !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDTYPE_PID;
task = pid_task(timr->it_pid, PIDTYPE_PID); ret = send_sigqueue(timr->sigq, timr->it_pid, type);
if (task) {
shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
ret = send_sigqueue(timr->sigq, task, shared);
}
rcu_read_unlock();
/* If we failed to send the signal the timer stops. */ /* If we failed to send the signal the timer stops. */
return ret > 0; return ret > 0;
} }