Remove now unnecessary inclusions of {asm,linux}/a.out.h.

[akpm@linux-foundation.org: fix alpha build]
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Suppress A.OUT library support if CONFIG_ARCH_SUPPORTS_AOUT is not set.

Not all architectures support the A.OUT binfmt, so the ELF binfmt should not
be permitted to go looking for A.OUT libraries to load in such a case.  Not
only that, but under such conditions A.OUT core dumps are not produced either.

To make this work, this patch also does the following:

 (1) Makes the existence of the contents of linux/a.out.h contingent on
     CONFIG_ARCH_SUPPORTS_AOUT.

 (2) Renames dump_thread() to aout_dump_thread() as it's only called by A.OUT
     core dumping code.

 (3) Moves aout_dump_thread() into asm/a.out-core.h and makes it inline.  This
     is then included only where needed.  This means that this bit of arch
     code will be stored in the appropriate A.OUT binfmt module rather than
     the core kernel.

 (4) Drops A.OUT support for Blackfin (according to Mike Frysinger it's not
     needed) and FRV.

This patch depends on the previous patch to move STACK_TOP[_MAX] out of
asm/a.out.h and into asm/processor.h as they're required whether or not A.OUT
format is available.

[jdike@addtoit.com: uml: re-remove accidentally restored code]
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: NJeff Dike <jdike@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Mark arches that support A.OUT format by including the following in their
master Kconfig files:

	config ARCH_SUPPORTS_AOUT
		def_bool y

This should also be set if the arch provides compatibility A.OUT support for
an older arch, for instance x86_64 for i386 or sparc64 for sparc.

I've guessed at which arches don't, based on comments in the code, however I'm
sure that some of the ones I've marked as 'yes' actually should be 'no'.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Move STACK_TOP[_MAX] out of asm/a.out.h and into asm/processor.h as they're
required whether or not A.OUT format is available.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix typo in comments.

BTW: I have to fix coding style in arch/ia64/kernel/time.c also, otherwise
checkpatch.pl will be complaining.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Function timekeeping_is_continuous() no longer checks flag
CLOCK_IS_CONTINUOUS, and it checks CLOCK_SOURCE_VALID_FOR_HRES now.  So rename
the function accordingly.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

list_for_each_safe() suffices here.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Flag CLOCK_SOURCE_WATCHDOG is cleared twice.  Note clocksource_change_rating()
won't do anyting with the cs flag.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There's only one caller left - the kill_pgrp one - so merge these two
functions and forget the kill_pgrp_info one.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Reviewed-by: NOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is the first step (of two) in removing the kill_pgrp_info.

All the users of this function are in kernel/signal.c, but all they need is to
call __kill_pgrp_info() with the tasklist_lock read-locked.

Fortunately, one of its users is the kill_something_info(), which already
needs this lock in one of its branches, so clean these branches up and call
the __kill_pgrp_info() directly.

Based on Oleg's view of how this function should look.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When sending the pid namespaces patches I wrongly converted the tsk->tgid into
task_pid_vnr(tsk) in mqueue-s (the git id of this patch is
b488893a).

The proper behavior is to get the task_tgid_vnr(tsk).

This seem to be the only mistake of that kind.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Some time ago the xxx_vnr() calls (e.g.  pid_vnr or find_task_by_vpid) were
_all_ converted to operate on the current pid namespace.  After this each call
like xxx_nr_ns(foo, current->nsproxy->pid_ns) is nothing but a xxx_vnr(foo)
one.

Switch all the xxx_nr_ns() callers to use the xxx_vnr() calls where
appropriate.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Reviewed-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

signal_struct->tsk points to the ->group_leader and thus we have the nasty
code in de_thread() which has to change it and restart ->real_timer if the
leader is changed.

Use "struct pid *leader_pid" instead.  This also allows us to kill now
unneeded send_group_sig_info().
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Acked-by: NRoland McGrath <roland@redhat.com>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There is a window when de_thread() switches the leader and drops
tasklist_lock.  In that window do_each_pid_task(PIDTYPE_PID) finds both new
and old leaders.

The problem is pretty much theoretical and probably can be ignored.  Currently
the only users of do_each_pid_task(PIDTYPE_PID) are send_sigio/send_sigurg, so
they can send the signal to the same process twice.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kill_pid_info()->pid_task() could be the old leader of the execing process.
In that case it is possible that the leader will be released before we take
siglock. This means that kill_pid_info() (and thus sys_kill()) can return a
false -ESRCH.

Change the code to retry when lock_task_sighand() fails. The endless loop is
not possible, __exit_signal() both clears ->sighand and does detach_pid().
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use task_pgrp_vnr not task_pgrp_nr so we return the process id the processes
pid namespace and not in the initial pid namespace.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

[m.kozlowski@tuxland.pl: fix unbalanced parenthesis in irix_BSDsetpgrp()]
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: NMariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With the new semantics of find_vpid() we don't need to play with ->nsproxy
explicitely, _vxx() do the right things.

Also s/tasklist/rcu/.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

pid_vnr returns the user space pid with respect to the pid namespace the
struct pid was allocated in.  What we want before we return a pid to user
space is the user space pid with respect to the pid namespace of current.

pid_vnr is a very nice optimization but because it isn't quite what we want
it is easy to use pid_vnr at times when we aren't certain the struct pid
was allocated in our pid namespace.

Currently this describes at least tiocgpgrp and tiocgsid in ttyio.c the
parent process reported in the core dumps and the parent process in
get_signal_to_deliver.

So unless the performance impact is huge having an interface that does what
we want instead of always what we want should be much more reliable and
much less error prone.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This modifies do_wait and eligible child to take a pair of enum pid_type
and struct pid *pid to precisely specify what set of processes are eligible
to be waited for, instead of the raw pid_t value from sys_wait4.

This fixes a bug in sys_waitid where you could not wait for children in
just process group 1.

This fixes a pid namespace crossing case in eligible_child.  Allowing us to
wait for a processes in our current process group even if our current
process group == 0.

This allows the no child with this pid case to be optimized.  This allows
us to optimize the pid membership test in eligible child to be optimized.

This even closes a theoretical pid wraparound race where in a threaded
parent if two threads are waiting for the same child and one thread picks
up the child and the pid numbers wrap around and generate another child
with that same pid before the other thread is scheduled (teribly insanely
unlikely) we could end up waiting on the second child with the same pid#
and not discover that the specific child we were waiting for has exited.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The previous bugfix was not optimal, we shouldn't care about group stop
when we are the only thread or the group stop is in progress.  In that case
nothing special is needed, just set PF_EXITING and return.

Also, take the related "TIF_SIGPENDING re-targeting" code from exit_notify().

So, from the performance POV the only difference is that we don't trust
!signal_pending() until we take ->siglock.  But this in fact fixes another
___pure___ theoretical minor race.  __group_complete_signal() finds the
task without PF_EXITING and chooses it as the target for signal_wake_up().
But nothing prevents this task from exiting in between without noticing the
pending signal and thus unpredictably delaying the actual delivery.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Eric's "fix clone(CLONE_NEWPID)" eliminated the last reason for this hack.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

do_signal_stop() counts all sub-thread and sets ->group_stop_count
accordingly.  Every thread should decrement ->group_stop_count and stop,
the last one should notify the parent.

However a sub-thread can exit before it notices the signal_pending(), or it
may be somewhere in do_exit() already.  In that case the group stop never
finishes properly.

Note: this is a minimal fix, we can add some optimizations later.  Say we
can return quickly if thread_group_empty().  Also, we can move some signal
related code from exit_notify() to exit_signals().
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NDavide Libenzi <davidel@xmailserver.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As Eric pointed out, there is no problem with init starting with sid == pgid
== 0, and this was historical linux behavior changed in 2.6.18.

Remove kernel_init()->__set_special_pids(), this is unneeded and complicates
the rules for sys_setsid().

This change and the previous change in daemonize() mean that /sbin/init does
not need the special "session != 1" hack in sys_setsid() any longer. We can't
remove this check yet, we should cleanup copy_process(CLONE_NEWPID) first, so
update the comment only.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Daemonized kernel threads run in the init's session. This doesn't match the
behaviour of kthread_create()'ed threads, and this is one of the 2 reasons
why we need a special hack in sys_setsid().

Now that set_special_pids() was changed to use struct pid, not pid_t, we can
use init_struct_pid and set 0,0 special pids.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Change set_special_pids() to work with struct pid, not pid_t from global name
space. This again speedups and imho cleanups the code, also a preparation for
the next patch.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

sys_setsid() still deals with pid_t's from the global namespace. This means
that the "session > 1" check can't help for sub-namespace init, setsid() can't
succeed because copy_process(CLONE_NEWPID) populates PIDTYPE_PGID/SID links.

Remove the usage of task_struct->pid and convert the code to use "struct pid".
This also simplifies and speedups the code, saves one find_pid().
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

sys_setpgid() does unneeded conversions from pid_t to "struct pid" and vice
versa.  Use "struct pid" more consistently.  Saves one find_vpid() and
eliminates the explicit usage of ->nsproxy->pid_ns.  Imho, cleanups the
code.

Also use the same_thread_group() helper.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NPavel Emelyanov <xemul@openvz.org>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The first "p->exit_state != EXIT_ZOMBIE" check doesn't make too much sense.
The exit_state was EXIT_ZOMBIE when the function was called, and another
thread can change it to EXIT_DEAD right after the check.

The second condition is not possible, detached non-traced threads were already
filtered out by eligible_child(), we didn't drop tasklist since then.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Surprise, the other two wait_task_*() functions also abuse the
task_pid_nr_ns() function, and may cause read-after-free or report nr == 0
in wait_task_continued().  wait_task_zombie() doesn't have this problem,
but it is still better to cache pid_t rather than call task_pid_nr_ns()
three times on the saved pid_namespace.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Imho, the current usage of security_task_wait() is not logical.

Suppose we have the single child p, and security_task_wait(p) return
-EANY.  In that case waitpid(-1) returns this error.  Why? Isn't it
better to return ECHLD? We don't really have reapable children.

Now suppose that child was stolen by gdb.  In that case we find this
child on ->ptrace_children and set flag = 1, but we don't check that the
child was denied.  So, do_wait(..., WNOHANG) returns 0, this doesn't
match the behaviour above.  Without WNOHANG do_wait() blocks only to
return the error later, when the child will be untraced.  Inho, really
strange.

I think eligible_child() should return the error only if the child's pid
was requested explicitly, otherwise we should silently ignore the tasks
which were nacked by security_task_wait().
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

eligible_child() == 2 means delay_group_leader().  With the previous patch
this only matters for EXIT_ZOMBIE task, we can move that special check to
the only place it is really needed.

Also, with this patch we don't skip security_task_wait() for the group
leaders in a non-empty thread group.  I don't really understand the exact
semantics of security_task_wait(), but imho this change is a bugfix.

Also rearrange the code a bit to kill an ugly "check_continued" backdoor.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Roland McGrath <roland@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

wait_task_stopped() doesn't need the "delay_group_leader" parameter.  If
the child is not traced it must be a group leader.  With or without
subthreads ->group_stop_count == 0 when the whole task is stopped.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Mika Penttila <mika.penttila@kolumbus.fi>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If the tracer is gone and we are not going to stop, ptrace_stop() sets
->exit_code = nostop_code.  However, the tracer could actually clear the
exit code before detaching.  In that case get_signal_to_deliver() "resends"
the signal which was cancelled by the debugger.  For example, it is
possible that a quick PTRACE_ATTACH + PTRACE_DETACH can leave the tracee in
STOPPED state.

Change the behaviour of ptrace_stop().  If the caller is ptrace notify(),
we should always clear ->exit_code.  If the caller is
get_signal_to_deliver(), we should not touch it at all.  To do so, change
the nonstop_code parameter to "bool clear_code" and change the callers
accordingly.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Every branch if the main "if" statement does the same code at the end.  Move
it down.  Also, fix the indentation.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

wait_task_stopped() has multiple races with SIGCONT/SIGKILL.  tasklist_lock
does not pin the child in TASK_TRACED/TASK_STOPPED stated, almost all info
reported (including exit_code) may be wrong.

In fact, the code under write_lock_irq(tasklist_lock) is not safe.  The child
may be PTRACE_DETACH'ed at this time by another subthread, in that case it is
possible we are no longer its ->parent.

Change wait_task_stopped() to take ->siglock before inspecting the task.  This
guarantees that the child can't resume and (for example) clear its
->exit_code, so we don't need to use xchg(&p->exit_code) and re-check.  The
only exception is ptrace_stop() which changes ->state and ->exit_code without
->siglock held during abort.  But this can only happen if both the tracer and
the tracee are dying (coredump is in progress), we don't care.

With this patch wait_task_stopped() doesn't move the child to the end of
the ->parent list on success.  This optimization could be restored, but
in that case we have to take write_lock(tasklist) and do some nasty
checks.

Also change the do_wait() since we don't return EAGAIN any longer.

[akpm@linux-foundation.org: fix up after Willy renamed everything]
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops
tasklist and then changes the ->state from TASK_TRACED to TASK_RUNNING.

This can fool another tracer which attaches to us in between.  Change the
->state under tasklist_lock to ensure that ptrace_check_attach() can't wrongly
succeed.  Also, remove the unnecessary mb().
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It is not possible to see the PT_PTRACED task without ->signal/sighand under
tasklist_lock, release_task() does ptrace_unlink() first.  If the task was
already released before, ptrace_attach() can't succeed and set PT_PTRACED.
Remove this check.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NRoland McGrath <roland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now that my_ptrace_child() is trivial we can use the "p->ptrace & PT_PTRACED"
inline and simplify the corresponding logic in do_wait: we can't find the
child in TASK_TRACED state without PT_PTRACED flag set, ptrace_untrace()
either sets TASK_STOPPED or wakes up the tracee.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NRoland McGrath <roland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since the patch

	"Fix ptrace_attach()/ptrace_traceme()/de_thread() race"
	commit f5b40e36

we set PT_ATTACHED and change child->parent "atomically" wrt task_list lock.

This means we can remove the checks like "PT_ATTACHED && ->parent != ptracer"
which were needed to catch the "ptrace attach is in progress" case.  We can
also remove the flag itself since nobody else uses it.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NRoland McGrath <roland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>