linux-toradex.git/kernel/exit.c, branch v3.14.3

exit: call disassociate_ctty() before exit_task_namespaces()

2014-04-27T00:19:07+00:00

commit c39df5fa37b0623589508c95515b4aa1531c524e upstream.

Commit 8aac62706ada ("move exit_task_namespaces() outside of
exit_notify()") breaks pppd and the exiting service crashes the kernel:

    BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
    IP: ppp_register_channel+0x13/0x20 [ppp_generic]
    Call Trace:
      ppp_asynctty_open+0x12b/0x170 [ppp_async]
      tty_ldisc_open.isra.2+0x27/0x60
      tty_ldisc_hangup+0x1e3/0x220
      __tty_hangup+0x2c4/0x440
      disassociate_ctty+0x61/0x270
      do_exit+0x7f2/0xa50

ppp_register_channel() needs ->net_ns and current->nsproxy == NULL.

Move disassociate_ctty() before exit_task_namespaces(), it doesn't make
sense to delay it after perf_event_exit_task() or cgroup_exit().

This also allows to use task_work_add() inside the (nontrivial) code
paths in disassociate_ctty().

Investigated by Peter Hurley.

Signed-off-by: Oleg Nesterov 
Reported-by: Sree Harsha Totakura 
Cc: Peter Hurley 
Cc: Sree Harsha Totakura 
Cc: "Eric W. Biederman" 
Cc: Jeff Dike 
Cc: Ingo Molnar 
Cc: Andrey Vagin 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

wait: fix reparent_leader() vs EXIT_DEAD->EXIT_ZOMBIE race

2014-04-27T00:19:07+00:00

commit dfccbb5e49a621c1b21a62527d61fc4305617aca upstream.

wait_task_zombie() first does EXIT_ZOMBIE->EXIT_DEAD transition and
drops tasklist_lock.  If this task is not the natural child and it is
traced, we change its state back to EXIT_ZOMBIE for ->real_parent.

The last transition is racy, this is even documented in 50b8d257486a
"ptrace: partially fix the do_wait(WEXITED) vs EXIT_DEAD->EXIT_ZOMBIE
race".  wait_consider_task() tries to detect this transition and clear
->notask_error but we can't rely on ptrace_reparented(), debugger can
exit and do ptrace_unlink() before its sub-thread sets EXIT_ZOMBIE.

And there is another problem which were missed before: this transition
can also race with reparent_leader() which doesn't reset >exit_signal if
EXIT_DEAD, assuming that this task must be reaped by someone else.  So
the tracee can be re-parented with ->exit_signal != SIGCHLD, and if
/sbin/init doesn't use __WALL it becomes unreapable.

Change reparent_leader() to update ->exit_signal even if EXIT_DEAD.
Note: this is the simple temporary hack for -stable, it doesn't try to
solve all problems, it will be reverted by the next changes.

Signed-off-by: Oleg Nesterov 
Reported-by: Jan Kratochvil 
Reported-by: Michal Schmidt 
Tested-by: Michal Schmidt 
Cc: Al Viro 
Cc: Lennart Poettering 
Cc: Roland McGrath 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

introduce for_each_thread() to replace the buggy while_each_thread()

2014-01-22T00:19:46+00:00

while_each_thread() and next_thread() should die, almost every lockless
usage is wrong.

1. Unless g == current, the lockless while_each_thread() is not safe.

   while_each_thread(g, t) can loop forever if g exits, next_thread()
   can't reach the unhashed thread in this case. Note that this can
   happen even if g is the group leader, it can exec.

2. Even if while_each_thread() itself was correct, people often use
   it wrongly.

   It was never safe to just take rcu_read_lock() and loop unless
   you verify that pid_alive(g) == T, even the first next_thread()
   can point to the already freed/reused memory.

This patch adds signal_struct->thread_head and task->thread_node to
create the normal rcu-safe list with the stable head.  The new
for_each_thread(g, t) helper is always safe under rcu_read_lock() as
long as this task_struct can't go away.

Note: of course it is ugly to have both task_struct->thread_node and the
old task_struct->thread_group, we will kill it later, after we change
the users of while_each_thread() to use for_each_thread().

Perhaps we can kill it even before we convert all users, we can
reimplement next_thread(t) using the new thread_head/thread_node.  But
we can't do this right now because this will lead to subtle behavioural
changes.  For example, do/while_each_thread() always sees at least one
task, while for_each_thread() can do nothing if the whole thread group
has died.  Or thread_group_empty(), currently its semantics is not clear
unless thread_group_leader(p) and we need to audit the callers before we
can change it.

So this patch adds the new interface which has to coexist with the old
one for some time, hopefully the next changes will be more or less
straightforward and the old one will go away soon.

Signed-off-by: Oleg Nesterov 
Reviewed-by: Sergey Dyasly 
Tested-by: Sergey Dyasly 
Reviewed-by: Sameer Nanda 
Acked-by: David Rientjes 
Cc: "Eric W. Biederman" 
Cc: Frederic Weisbecker 
Cc: Mandeep Singh Baines 
Cc: "Ma, Xindong" 
Cc: Michal Hocko 
Cc: "Tu, Xiaobing" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace: revert "Prepare to fix racy accesses on task breakpoints"

2013-07-09T17:33:26+00:00

This reverts commit bf26c018490c ("Prepare to fix racy accesses on task
breakpoints").

The patch was fine but we can no longer race with SIGKILL after commit
9899d11f6544 ("ptrace: ensure arch_ptrace/ptrace_request can never race
with SIGKILL"), the __TASK_TRACED tracee can't be woken up and
->ptrace_bps[] can't go away.

Now that ptrace_get_breakpoints/ptrace_put_breakpoints have no callers,
we can kill them and remove task->ptrace_bp_refcnt.

Signed-off-by: Oleg Nesterov 
Acked-by: Frederic Weisbecker 
Acked-by: Michael Neuling 
Cc: Benjamin Herrenschmidt 
Cc: Ingo Molnar 
Cc: Jan Kratochvil 
Cc: Paul Mackerras 
Cc: Paul Mundt 
Cc: Will Deacon 
Cc: Prasad 
Cc: Russell King 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'akpm' (updates from Andrew Morton)

2013-07-04T00:12:13+00:00

Merge first patch-bomb from Andrew Morton:
 - various misc bits
 - I'm been patchmonkeying ocfs2 for a while, as Joel and Mark have been
   distracted.  There has been quite a bit of activity.
 - About half the MM queue
 - Some backlight bits
 - Various lib/ updates
 - checkpatch updates
 - zillions more little rtc patches
 - ptrace
 - signals
 - exec
 - procfs
 - rapidio
 - nbd
 - aoe
 - pps
 - memstick
 - tools/testing/selftests updates

* emailed patches from Andrew Morton : (445 commits)
  tools/testing/selftests: don't assume the x bit is set on scripts
  selftests: add .gitignore for kcmp
  selftests: fix clean target in kcmp Makefile
  selftests: add .gitignore for vm
  selftests: add hugetlbfstest
  self-test: fix make clean
  selftests: exit 1 on failure
  kernel/resource.c: remove the unneeded assignment in function __find_resource
  aio: fix wrong comment in aio_complete()
  drivers/w1/slaves/w1_ds2408.c: add magic sequence to disable P0 test mode
  drivers/memstick/host/r592.c: convert to module_pci_driver
  drivers/memstick/host/jmb38x_ms: convert to module_pci_driver
  pps-gpio: add device-tree binding and support
  drivers/pps/clients/pps-gpio.c: convert to module_platform_driver
  drivers/pps/clients/pps-gpio.c: convert to devm_* helpers
  drivers/parport/share.c: use kzalloc
  Documentation/accounting/getdelays.c: avoid strncpy in accounting tool
  aoe: update internal version number to v83
  aoe: update copyright date
  aoe: perform I/O completions in parallel
  ...

exit.c: unexport __set_special_pids()

2013-07-03T23:08:02+00:00

Move __set_special_pids() from exit.c to sys.c close to its single caller
and make it static.

And rename it to set_special_pids(), another helper with this name has
gone away.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'freezer'

2013-06-28T11:00:53+00:00

* freezer:
  af_unix: use freezable blocking calls in read
  sigtimedwait: use freezable blocking call
  nanosleep: use freezable blocking call
  futex: use freezable blocking call
  select: use freezable blocking call
  epoll: use freezable blocking call
  binder: use freezable blocking calls
  freezer: add new freezable helpers using freezer_do_not_count()
  freezer: convert freezable helpers to static inline where possible
  freezer: convert freezable helpers to freezer_do_not_count()
  freezer: skip waking up tasks with PF_FREEZER_SKIP set
  freezer: shorten freezer sleep time using exponential backoff
  lockdep: check that no locks held at freeze time
  lockdep: remove task argument from debug_check_no_locks_held
  freezer: add unsafe versions of freezable helpers for CIFS
  freezer: add unsafe versions of freezable helpers for NFS

move exit_task_namespaces() outside of exit_notify()

2013-06-15T01:39:08+00:00

exit_notify() does exit_task_namespaces() after
forget_original_parent(). This was needed to ensure that ->nsproxy
can't be cleared prematurely, an exiting child we are going to
reparent can do do_notify_parent() and use the parent's (ours) pid_ns.

However, after 32084504 "pidns: use task_active_pid_ns in
do_notify_parent" ->nsproxy != NULL is no longer needed, we rely
on task_active_pid_ns().

Move exit_task_namespaces() from exit_notify() to do_exit(), after
exit_fs() and before exit_task_work().

This solves the problem reported by Andrey, free_ipc_ns()->shm_destroy()
does fput() which needs task_work_add().

Note: this particular problem can be fixed if we change fput(), and
that change makes sense anyway. But there is another reason to move
the callsite. The original reason for exit_task_namespaces() from
the middle of exit_notify() was subtle and it has already gone away,
now this looks confusing. And this allows us do simplify exit_notify(),
we can avoid unlock/lock(tasklist) and we can use ->exit_state instead
of PF_EXITING in forget_original_parent().

Reported-by: Andrey Vagin 
Signed-off-by: Oleg Nesterov 
Acked-by: "Eric W. Biederman" 
Acked-by: Andrey Vagin 
Signed-off-by: Al Viro

lockdep: remove task argument from debug_check_no_locks_held

2013-05-12T12:16:21+00:00

The only existing caller to debug_check_no_locks_held calls it
with 'current' as the task, and the freezer needs to call
debug_check_no_locks_held but doesn't already have a current
task pointer, so remove the argument.  It is already assuming
that the current task is relevant by dumping the current stack
trace as part of the warning.

This was originally part of 6aa9707099c (lockdep: check that
no locks held at freeze time) which was reverted in
dbf520a9d7d4.

Original-author: Mandeep Singh Baines 
Acked-by: Pavel Machek 
Acked-by: Tejun Heo 
Signed-off-by: Colin Cross 
Signed-off-by: Rafael J. Wysocki

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2013-05-02T00:51:54+00:00

Pull VFS updates from Al Viro,

Misc cleanups all over the place, mainly wrt /proc interfaces (switch
create_proc_entry to proc_create(), get rid of the deprecated
create_proc_read_entry() in favor of using proc_create_data() and
seq_file etc).

7kloc removed.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (204 commits)
  don't bother with deferred freeing of fdtables
  proc: Move non-public stuff from linux/proc_fs.h to fs/proc/internal.h
  proc: Make the PROC_I() and PDE() macros internal to procfs
  proc: Supply a function to remove a proc entry by PDE
  take cgroup_open() and cpuset_open() to fs/proc/base.c
  ppc: Clean up scanlog
  ppc: Clean up rtas_flash driver somewhat
  hostap: proc: Use remove_proc_subtree()
  drm: proc: Use remove_proc_subtree()
  drm: proc: Use minor->index to label things, not PDE->name
  drm: Constify drm_proc_list[]
  zoran: Don't print proc_dir_entry data in debug
  reiserfs: Don't access the proc_dir_entry in r_open(), r_start() r_show()
  proc: Supply an accessor for getting the data from a PDE's parent
  airo: Use remove_proc_subtree()
  rtl8192u: Don't need to save device proc dir PDE
  rtl8187se: Use a dir under /proc/net/r8180/
  proc: Add proc_mkdir_data()
  proc: Move some bits from linux/proc_fs.h to linux/{of.h,signal.h,tty.h}
  proc: Move PDE_NET() to fs/proc/proc_net.c
  ...