The previous commit (45c18b0bb5, aka "Fix
unlikely (but possible) race condition on task->user access") fixed a
potential oops due to __sigqueue_alloc() getting its "user" pointer out
of sync with switch_user(), and accessing a user pointer that had been
de-allocated on another CPU.
It still left another (much less serious) problem, where a concurrent
__sigqueue_alloc and swich_user could cause sigqueue_alloc to do signal
pending reference counting for a _different_ user than the one it then
actually ended up using. No oops, but we'd end up with the wrong signal
accounting.
Another case of Oleg's eagle-eyes picking up the problem.
This is trivially fixed by just making sure we load whichever "user"
structure we decide to use (it doesn't matter _which_ one we pick, we
just need to pick one) just once.
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The problem with remembering a user space process by its pid is that it is
possible that the process will exit, pid wrap around will occur.
Converting to a struct pid avoid that problem, and paves the way for
implementing a pid namespace.
Also since usb is the only user of kill_proc_info_as_uid rename
kill_proc_info_as_uid to kill_pid_info_as_uid and have the new version take
a struct pid.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Currently the signal functions all either take a task or a pid_t argument.
This patch implements variants that take a struct pid *. After all of the
users have been update it is my intention to remove the variants that take a
pid_t as using pid_t can be more work (an extra hash table lookup) and
difficult to get right in the presence of multiple pid namespaces.
There are two kinds of functions introduced in this patch. The are the
general use functions kill_pgrp and kill_pid which take a priv argument that
is ultimately used to create the appropriate siginfo information, Then there
are _kill_pgrp_info, kill_pgrp_info, kill_pid_info the internal implementation
helpers that take an explicit siginfo.
The distinction is made because filling out an explcit siginfo is tricky, and
will be even more tricky when pid namespaces are introduced.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This tightens up __dequeue_signal a little. It also avoids doing
recalc_sigpending twice in a row, instead doing it once in dequeue_signal.
Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Move the fallback arch_vma_name() to a sensible place (kernel/signal.c).
Currently it's in fs/proc/task_mmu.c, a file that is dependent on both
CONFIG_PROC_FS and CONFIG_MMU being enabled, but it's used from
kernel/signal.c from where it is called unconditionally.
[akpm@osdl.org: build fix]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Suresh points out that commit b0423a0d9c
broke the semantics of a synchronous signal like SIGSEGV occurring
recursively inside its own handler handler (or, indeed, any other
context when the signal was blocked).
That was unintentional, and this fixes things up by reinstating the old
semantics, but without reverting the cleanups.
Cc: Paul E. McKenney <paulmck@us.ibm.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch adds a call to the extended security_task_kill hook introduced by
the prior patch to the kill_proc_info_as_uid function so that these signals
can be properly mediated by security modules. It also updates the existing
hook call in check_kill_permission.
Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
With this patch zap_process() sets SIGNAL_GROUP_EXIT while sending SIGKILL to
the thread group. This means that a TASK_TRACED task
1. Will be awakened by signal_wake_up(1)
2. Can't sleep again via ptrace_notify()
3. Can't go to do_signal_stop() after return
from ptrace_stop() in get_signal_to_deliver()
So we can remove all ptrace related stuff from coredump path.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This reverts most of commit 30e0fca6c1.
It broke the case of non-leader MT exec when ptraced.
I think the bug it was intended to fix was already addressed by commit
788e05a67c.
Signed-off-by: Roland McGrath <roland@redhat.com>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Commit e56d090310
[PATCH] RCU signal handling
made this BUG_ON() unsafe. This code runs under ->siglock,
while switch_exec_pids() takes tasklist_lock.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
this changes if() BUG(); constructs to BUG_ON() which is
cleaner, contains unlikely() and can better optimized away.
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
strace /bin/bash misbehaves after resume; this fixes it.
(akpm: it's scary calling refrigerator() in state TASK_TRACED, but it seems to
do the right thing).
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
send_sigqueue() checks PF_EXITING, then locks p->sighand->siglock. This is
unsafe: 'p' can exit in between and set ->sighand = NULL. The race is
theoretical, the window is tiny and irqs are disabled by the caller, so I
don't think we need the fix for -stable tree.
Convert send_sigqueue() to use lock_task_sighand() helper.
Also, delete 'p->flags & PF_EXITING' re-check, it is unneeded and the
comment is wrong.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The previous patch has changed callsites of do_notify_parent_cldstop() so that
to_self == (->ptrace & PT_PTRACED) always (as it should be). We can remove
this parameter now.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove an obscure 'stop_count < 0' check in finish_stop(). The previous patch
made this case impossible.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
do_signal_stop() considers 'thread_group_empty()' as a special case.
This was needed to avoid taking tasklist_lock. Since this lock is
unneeded any longer, we can remove this special case and simplify
the code even more.
Also, before this patch, finish_stop() was called with stop_count == -1
for 'thread_group_empty()' case. This is not strictly wrong, but confusing
and unneeded.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
do_sigaction() does not need tasklist_lock anymore, we can simplify the code.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
do_signal_stop() does not need tasklist_lock anymore. So it does not need to
do misc re-checks, and we can simplify the code.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
handle_stop_signal() does not need tasklist_lock for SIG_KERNEL_STOP_MASK
signals anymore.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
__exit_signal() is private to release_task() now. I think it is better to
make it static in kernel/exit.c and export flush_sigqueue() instead - this
function is much more simple and straightforward.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Cosmetic, rename __exit_sighand to cleanup_sighand and move it close to
copy_sighand().
This matches copy_signal/cleanup_signal naming, and I think it is easier to
follow.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
__exit_signal() does important cleanups atomically under ->siglock. It is
also called from copy_process's error path. This is not good, for example we
can't move __unhash_process() under ->siglock for that reason.
We should not mix these 2 paths, just look at ugly 'if (p->sighand)' under
'bad_fork_cleanup_sighand:' label. For copy_process() case it is sufficient
to just backout copy_signal(), nothing more.
Again, nobody can see this task yet. For CLONE_THREAD case we just decrement
signal->count, otherwise nobody can see this ->signal and we can free it
lockless.
This patch assumes it is safe to do exit_thread_group_keys() without
tasklist_lock.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The only caller of exit_sighand(tsk) is copy_process's error path. We can
call __exit_sighand() directly and kill exit_sighand().
This 'tsk' was not yet registered in pid_hash[] or init_task.tasks, it has no
external references, nobody can see it, and
IF (clone_flags & CLONE_SIGHAND)
At least 'current' has a reference to ->sighand, this
means atomic_dec_and_test(sighand->count) can't be true.
ELSE
Nobody can see this ->sighand, this means we can free it
without any locking.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In my opinion this patch cleans up the code.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add lock_task_sighand() helper and converts group_send_sig_info() to use
it. Hopefully we will have more users soon.
This patch also removes '!sighand->count' and '!p->usage' checks, I think
they both are bogus, racy and unneeded (but probably it makes sense to
restore them as BUG_ON()s).
->sighand is cleared and it's ->count is decremented in release_task() with
sighand->siglock held, so it is a bug to have '!p->usage || !->count' after
we already locked and verified it is the same. On the other hand, an
already dead task without ->sighand can have a non-zero ->usage due to
ptrace, for example.
If we read the stale value of ->sighand we must see the change after
spin_lock(), because that change was done while holding that same old
->sighand.siglock.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch borrows a clever Hugh's 'struct anon_vma' trick.
Without tasklist_lock held we can't trust task->sighand until we locked it
and re-checked that it is still the same.
But this means we don't need to defer 'kmem_cache_free(sighand)'. We can
return the memory to slab immediately, all we need is to be sure that
sighand->siglock can't dissapear inside rcu protected section.
To do so we need to initialize ->siglock inside ctor function,
SLAB_DESTROY_BY_RCU does the rest.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
After looking at the problem of init calling exec some more I figured out
an easy way to make the code work.
The actual symptom without out this patch is that all threads will die
except pid == 1, and the thread calling exec. The thread calling exec will
wait forever for pid == 1 to die.
Since pid == 1 does not install a handler for SIGKILL it will never die.
This modifies the tests for init from current->pid == 1 to the equivalent
current == child_reaper. And then it causes exec in the ugly case to
modify child_reaper.
The only weird symptom is that you wind up with an init process that
doesn't have the oldest start time on the box.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch from Pavel moves userland freeze signals handling into more logical
place. It now hits even with mysqld running.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Pointed out by Linus Torvalds.
sys_signal() forgets to initialize ->sa_mask.
( I suspect arch/ia64/ia32/ia32_signal.c:sys32_signal()
also needs this fix )
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Five callsites. I dunno how all this crap got back in there :(
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The TIF_RESTORE_SIGMASK flag allows us to have a generic implementation of
sys_rt_sigsuspend() instead of duplicating it for each architecture. This
provides such an implementation and makes arch/powerpc use it.
It also tidies up the ppc32 sys_sigsuspend() to use TIF_RESTORE_SIGMASK.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove the "inline" keyword from a bunch of big functions in the kernel with
the goal of shrinking it by 30kb to 40kb
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- Move capable() from sched.h to capability.h;
- Use <linux/capability.h> where capable() is used
(in include/, block/, ipc/, kernel/, a few drivers/,
mm/, security/, & sound/;
many more drivers/ to go)
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch removes unneeded sig->curr_target recalculation under 'if
(atomic_dec_and_test(&sig->count))' in __exit_signal().
When sig->count == 0 the signal can't be sent to this task and
next_thread(tsk) == tsk anyway.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
While rooting aroung in the signal code trying to understand how to fix the
SIG_IGN ploy (set sig handler to SIG_IGN and flood system with high speed
repeating timers) I came across what, I think, is a problem in sigaction()
in that when processing a SIG_IGN request it flushes signals from 1 to
SIGRTMIN and leaves the rest. Attempt to fix this.
Signed-off-by: George Anzinger <george@mvista.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Some simplification in checking signal delivery against concurrent exit.
Instead of using get_task_struct_rcu(), which increments the task_struct
reference count, check the reference count after acquiring sighand lock.
Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
RCU tasklist_lock and RCU signal handling: send signals RCU-read-locked
instead of tasklist_lock read-locked. This is a scalability improvement on
SMP and a preemption-latency improvement under PREEMPT_RCU.
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: William Irwin <wli@holomorphy.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch reverts commit c33880aadd since
it's not needed anymore. As pointed out by Roland McGrath the real fix
is to deliver all signals before returning to user space.
See http://www.ussg.iu.edu/hypermail/linux/kernel/0509.2/0683.html
A fix for s390 has been merged.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If a task is being traced we never auto-reap it even if it might look
like its parent doesn't care. The tracer obviously _does_ care.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Combine a bit of redundant code between force_sig_info() and
force_sig_specific().
Signed-off-by: paulmck@us.ibm.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch removes checks for ->si_code == SI_TIMER from send_signal,
specific_send_sig_info, __group_send_sig_info.
I think posix-timers.c used these functions some time ago, now it sends
signals via send_{,group_}sigqueue, so these hooks are unneeded.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch simplifies some checks for magic siginfo values. It should not
change the behaviour in any way.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch replaces hardcoded SEND_SIG_xxx constants with
their symbolic names.
No changes in affected .o files.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Linus Torvalds
Eric W. Biederman
Roland McGrath
David Howells
David Quigley
Jörn Engel
Oleg Nesterov
Al Viro
Eric Sesterhenn
Pavel Machek
Rafael J. Wysocki
Andrew Morton
David Woodhouse
Arjan van de Ven
Randy.Dunlap
George Anzinger
Paul E. McKenney
Ingo Molnar
Heiko Carstens