linux.git/kernel/exit.c, branch v3.5-rc1

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

2012-06-01T01:47:30+00:00

Pull second pile of signal handling patches from Al Viro:
 "This one is just task_work_add() series + remaining prereqs for it.

  There probably will be another pull request from that tree this
  cycle - at least for helpers, to get them out of the way for per-arch
  fixes remaining in the tree."

Fix trivial conflict in kernel/irq/manage.c: the merge of Andrew's pile
had brought in commit 97fd75b7b8e0 ("kernel/irq/manage.c: use the
pr_foo() infrastructure to prefix printks") which changed one of the
pr_err() calls that this merge moves around.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal:
  keys: kill task_struct->replacement_session_keyring
  keys: kill the dummy key_replace_session_keyring()
  keys: change keyctl_session_to_parent() to use task_work_add()
  genirq: reimplement exit_irq_thread() hook via task_work_add()
  task_work_add: generic process-context callbacks
  avr32: missed _TIF_NOTIFY_RESUME on one of do_notify_resume callers
  parisc: need to check NOTIFY_RESUME when exiting from syscall
  move key_repace_session_keyring() into tracehook_notify_resume()
  TIF_NOTIFY_RESUME is defined on all targets now

stack usage: add pid to warning printk in check_stack_usage

2012-06-01T00:49:28+00:00

In embedded systems, sometimes the same program (busybox) is the cause of
multiple warnings.  Outputting the pid with the program name in the
warning printk helps distinguish which instances of a program are using
the stack most.

This is a small patch, but useful.

Signed-off-by: Tim Bird 
Cc: Oleg Nesterov 
Cc: Frederic Weisbecker 
Cc: Andrea Arcangeli 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cred: remove task_is_dead() from __task_cred() validation

2012-06-01T00:49:28+00:00

Commit 8f92054e7ca1 ("CRED: Fix __task_cred()'s lockdep check and banner
comment"):

    add the following validation condition:

        task->exit_state >= 0

    to permit the access if the target task is dead and therefore
    unable to change its own credentials.

OK, but afaics currently this can only help wait_task_zombie() which calls
__task_cred() without rcu lock.

Remove this validation and change wait_task_zombie() to use task_uid()
instead.  This means we do rcu_read_lock() only to shut up the lockdep,
but we already do the same in, say, wait_task_stopped().

task_is_dead() should die, task->exit_state != 0 means that this task has
passed exit_notify(), only do_wait-like code paths should use this.

Unfortunately, we can't kill task_is_dead() right now, it has already
acquired buggy users in drivers/staging.  The fix already exists.

Signed-off-by: Oleg Nesterov 
Reviewed-by: "Eric W. Biederman" 
Acked-by: David Howells 
Cc: Jiri Olsa 
Cc: Paul E. McKenney 
Cc: James Morris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

genirq: reimplement exit_irq_thread() hook via task_work_add()

2012-05-24T02:11:12+00:00

exit_irq_thread() and task->irq_thread are needed to handle the unexpected
(and unlikely) exit of irq-thread.

We can use task_work instead and make this all private to
kernel/irq/manage.c, cleanup plus micro-optimization.

1. rename exit_irq_thread() to irq_thread_dtor(), make it
   static, and move it up before irq_thread().

2. change irq_thread() to do task_work_add(irq_thread_dtor)
   at the start and task_work_cancel() before return.

   tracehook_notify_resume() can never play with kthreads,
   only do_exit()->exit_task_work() can call the callback
   and this is what we want.

3. remove task_struct->irq_thread and the special hook
   in do_exit().

Signed-off-by: Oleg Nesterov 
Reviewed-by: Thomas Gleixner 
Cc: David Howells 
Cc: Richard Kuo 
Cc: Linus Torvalds 
Cc: Alexander Gordeev 
Cc: Chris Zankel 
Cc: David Smith 
Cc: "Frank Ch. Eigler" 
Cc: Geert Uytterhoeven 
Cc: Larry Woodman 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Al Viro

task_work_add: generic process-context callbacks

2012-05-24T02:09:21+00:00

Provide a simple mechanism that allows running code in the (nonatomic)
context of the arbitrary task.

The caller does task_work_add(task, task_work) and this task executes
task_work->func() either from do_notify_resume() or from do_exit().  The
callback can rely on PF_EXITING to detect the latter case.

"struct task_work" can be embedded in another struct, still it has "void
*data" to handle the most common/simple case.

This allows us to kill the ->replacement_session_keyring hack, and
potentially this can have more users.

Performance-wise, this adds 2 "unlikely(!hlist_empty())" checks into
tracehook_notify_resume() and do_exit().  But at the same time we can
remove the "replacement_session_keyring != NULL" checks from
arch/*/signal.c and exit_creds().

Note: task_work_add/task_work_run abuses ->pi_lock.  This is only because
this lock is already used by lookup_pi_state() to synchronize with
do_exit() setting PF_EXITING.  Fortunately the scope of this lock in
task_work.c is really tiny, and the code is unlikely anyway.

Signed-off-by: Oleg Nesterov 
Acked-by: David Howells 
Cc: Thomas Gleixner 
Cc: Richard Kuo 
Cc: Linus Torvalds 
Cc: Alexander Gordeev 
Cc: Chris Zankel 
Cc: David Smith 
Cc: "Frank Ch. Eigler" 
Cc: Geert Uytterhoeven 
Cc: Larry Woodman 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Al Viro

cred: use correct cred accessor with regards to rcu read lock

2012-05-17T22:50:06+00:00

Commit "userns: Convert setting and getting uid and gid system calls to use
kuid and kgid has modified the accessors in wait_task_continued() and
wait_task_stopped() to use __task_cred() instead of task_uid().

__task_cred() assumes that we're inside a rcu read lock, which is untrue
for these two functions.

Modify it to use task_uid() instead.

Signed-off-by: Sasha Levin 
Signed-off-by: Eric W. Biederman

userns: Convert setting and getting uid and gid system calls to use kuid and kgid

2012-05-03T10:28:41+00:00

Convert setregid, setgid, setreuid, setuid,
setresuid, getresuid, setresgid, getresgid, setfsuid, setfsgid,
getuid, geteuid, getgid, getegid,
waitpid, waitid, wait4.

Convert userspace uids and gids into kuids and kgids before
being placed on struct cred.  Convert struct cred kuids and
kgids into userspace uids and gids when returning them.

Signed-off-by: Eric W. Biederman

Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-03-30T01:12:23+00:00

Pull x32 support for x86-64 from Ingo Molnar:
 "This tree introduces the X32 binary format and execution mode for x86:
  32-bit data space binaries using 64-bit instructions and 64-bit kernel
  syscalls.

  This allows applications whose working set fits into a 32 bits address
  space to make use of 64-bit instructions while using a 32-bit address
  space with shorter pointers, more compressed data structures, etc."

Fix up trivial context conflicts in arch/x86/{Kconfig,vdso/vma.c}

* 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (71 commits)
  x32: Fix alignment fail in struct compat_siginfo
  x32: Fix stupid ia32/x32 inversion in the siginfo format
  x32: Add ptrace for x32
  x32: Switch to a 64-bit clock_t
  x32: Provide separate is_ia32_task() and is_x32_task() predicates
  x86, mtrr: Use explicit sizing and padding for the 64-bit ioctls
  x86/x32: Fix the binutils auto-detect
  x32: Warn and disable rather than error if binutils too old
  x32: Only clear TIF_X32 flag once
  x32: Make sure TS_COMPAT is cleared for x32 tasks
  fs: Remove missed ->fds_bits from cessation use of fd_set structs internally
  fs: Fix close_on_exec pointer in alloc_fdtable
  x32: Drop non-__vdso weak symbols from the x32 VDSO
  x32: Fix coding style violations in the x32 VDSO code
  x32: Add x32 VDSO support
  x32: Allow x32 to be configured
  x32: If configured, add x32 system calls to system call tables
  x32: Handle process creation
  x32: Signal-related system calls
  x86: Add #ifdef CONFIG_COMPAT to 
  ...

kernel/exit.c: if init dies, log a signal which killed it, if any

2012-03-23T23:58:32+00:00

I just received another user's pleas for help when their init
mysteriously died.  I again explained that they need to check whether it
died because of bad instruction, a segv, or something else.  Which was
an annoying detour into writing a trivial C program to spawn his init
and print its exit code:

  http://lists.busybox.net/pipermail/busybox/2012-January/077172.html

I hear you saying "just test it under /bin/sh".  Well, the crashing init
_was_ /bin/sh.

Which prompted me to make kernel do this first step automatically.  We can
print exit code, which makes it possible to see that death was from e.g.
SIGILL without writing test programs.

[akpm@linux-foundation.org: add 0x to hex number output]
Signed-off-by: Denys Vlasenko 
Acked-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

prctl: add PR_{SET,GET}_CHILD_SUBREAPER to allow simple process supervision

2012-03-23T23:58:32+00:00

Userspace service managers/supervisors need to track their started
services.  Many services daemonize by double-forking and get implicitly
re-parented to PID 1.  The service manager will no longer be able to
receive the SIGCHLD signals for them, and is no longer in charge of
reaping the children with wait().  All information about the children is
lost at the moment PID 1 cleans up the re-parented processes.

With this prctl, a service manager process can mark itself as a sort of
'sub-init', able to stay as the parent for all orphaned processes
created by the started services.  All SIGCHLD signals will be delivered
to the service manager.

Receiving SIGCHLD and doing wait() is in cases of a service-manager much
preferred over any possible asynchronous notification about specific
PIDs, because the service manager has full access to the child process
data in /proc and the PID can not be re-used until the wait(), the
service-manager itself is in charge of, has happened.

As a side effect, the relevant parent PID information does not get lost
by a double-fork, which results in a more elaborate process tree and
'ps' output:

before:
  # ps afx
  253 ?        Ss     0:00 /bin/dbus-daemon --system --nofork
  294 ?        Sl     0:00 /usr/libexec/polkit-1/polkitd
  328 ?        S      0:00 /usr/sbin/modem-manager
  608 ?        Sl     0:00 /usr/libexec/colord
  658 ?        Sl     0:00 /usr/libexec/upowerd
  819 ?        Sl     0:00 /usr/libexec/imsettings-daemon
  916 ?        Sl     0:00 /usr/libexec/udisks-daemon
  917 ?        S      0:00  \_ udisks-daemon: not polling any devices

after:
  # ps afx
  294 ?        Ss     0:00 /bin/dbus-daemon --system --nofork
  426 ?        Sl     0:00  \_ /usr/libexec/polkit-1/polkitd
  449 ?        S      0:00  \_ /usr/sbin/modem-manager
  635 ?        Sl     0:00  \_ /usr/libexec/colord
  705 ?        Sl     0:00  \_ /usr/libexec/upowerd
  959 ?        Sl     0:00  \_ /usr/libexec/udisks-daemon
  960 ?        S      0:00  |   \_ udisks-daemon: not polling any devices
  977 ?        Sl     0:00  \_ /usr/libexec/packagekitd

This prctl is orthogonal to PID namespaces.  PID namespaces are isolated
from each other, while a service management process usually requires the
services to live in the same namespace, to be able to talk to each
other.

Users of this will be the systemd per-user instance, which provides
init-like functionality for the user's login session and D-Bus, which
activates bus services on-demand.  Both need init-like capabilities to
be able to properly keep track of the services they start.

Many thanks to Oleg for several rounds of review and insights.

[akpm@linux-foundation.org: fix comment layout and spelling]
[akpm@linux-foundation.org: add lengthy code comment from Oleg]
Reviewed-by: Oleg Nesterov 
Signed-off-by: Lennart Poettering 
Signed-off-by: Kay Sievers 
Acked-by: Valdis Kletnieks 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds