linux-toradex.git/fs/exec.c, branch v3.3.5

exit_signal: simplify the "we have changed execution domain" logic

2012-05-07T15:53:35+00:00

commit e636825346b36a07ccfc8e30946d52855e21f681 upstream.

exit_notify() checks "tsk->self_exec_id != tsk->parent_exec_id"
to handle the "we have changed execution domain" case.

We can change do_thread() to always set ->exit_signal = SIGCHLD
and remove this check to simplify the code.

We could change setup_new_exec() instead, this looks more logical
because it increments ->self_exec_id. But note that de_thread()
already resets ->exit_signal if it changes the leader, let's keep
both changes close to each other.

Note that we change ->exit_signal lockless, this changes the rules.
Thereafter ->exit_signal is not stable under tasklist but this is
fine, the only possible change is OLDSIG -> SIGCHLD. This can race
with eligible_child() but the race is harmless. We can race with
reparent_leader() which changes our ->exit_signal in parallel, but
it does the same change to SIGCHLD.

The noticeable user-visible change is that the execing task is not
"visible" to do_wait()->eligible_child(__WCLONE) right after exec.
To me this looks more logical, and this is consistent with mt case.

Signed-off-by: Oleg Nesterov 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

coredump_wait: don't call complete_vfork_done()

2012-03-05T23:49:42+00:00

Now that CLONE_VFORK is killable, coredump_wait() no longer needs
complete_vfork_done().  zap_threads() should find and kill all tasks with
the same ->mm, this includes our parent if ->vfork_done is set.

mm_release() becomes the only caller, unexport complete_vfork_done().

Signed-off-by: Oleg Nesterov 
Acked-by: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vfork: introduce complete_vfork_done()

2012-03-05T23:49:42+00:00

No functional changes.

Move the clear-and-complete-vfork_done code into the new trivial helper,
complete_vfork_done().

Signed-off-by: Oleg Nesterov 
Acked-by: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

exec: fix use-after-free bug in setup_new_exec()

2012-02-06T23:15:20+00:00

Setting the task name is done within setup_new_exec() by accessing
bprm->filename. However this happens after flush_old_exec().
This may result in a use after free bug, flush_old_exec() may
"complete" vfork_done, which will wake up the parent which in turn
may free the passed in filename.
To fix this add a new tcomm field in struct linux_binprm which
contains the now early generated task name until it is used.

Fixes this bug on s390:

  Unable to handle kernel pointer dereference at virtual kernel address 0000000039768000
  Process kworker/u:3 (pid: 245, task: 000000003a3dc840, ksp: 0000000039453818)
  Krnl PSW : 0704000180000000 0000000000282e94 (setup_new_exec+0xa0/0x374)
  Call Trace:
  ([<0000000000282e2c>] setup_new_exec+0x38/0x374)
   [<00000000002dd12e>] load_elf_binary+0x402/0x1bf4
   [<0000000000280a42>] search_binary_handler+0x38e/0x5bc
   [<0000000000282b6c>] do_execve_common+0x410/0x514
   [<0000000000282cb6>] do_execve+0x46/0x58
   [<00000000005bce58>] kernel_execve+0x28/0x70
   [<000000000014ba2e>] ____call_usermodehelper+0x102/0x140
   [<00000000005bc8da>] kernel_thread_starter+0x6/0xc
   [<00000000005bc8d4>] kernel_thread_starter+0x0/0xc
  Last Breaking-Event-Address:
   [<00000000002830f0>] setup_new_exec+0x2fc/0x374

  Kernel panic - not syncing: Fatal exception: panic_on_oops

Reported-by: Sebastian Ott 
Signed-off-by: Heiko Carstens 
Signed-off-by: Linus Torvalds

tracepoint: add tracepoints for debugging oom_score_adj

2012-01-11T00:30:44+00:00

oom_score_adj is used for guarding processes from OOM-Killer.  One of
problem is that it's inherited at fork().  When a daemon set oom_score_adj
and make children, it's hard to know where the value is set.

This patch adds some tracepoints useful for debugging. This patch adds
3 trace points.
  - creating new task
  - renaming a task (exec)
  - set oom_score_adj

To debug, users need to enable some trace pointer. Maybe filtering is useful as

# EVENT=/sys/kernel/debug/tracing/events/task/
# echo "oom_score_adj != 0" > $EVENT/task_newtask/filter
# echo "oom_score_adj != 0" > $EVENT/task_rename/filter
# echo 1 > $EVENT/enable
# EVENT=/sys/kernel/debug/tracing/events/oom/
# echo 1 > $EVENT/enable

output will be like this.
# grep oom /sys/kernel/debug/tracing/trace
bash-7699  [007] d..3  5140.744510: oom_score_adj_update: pid=7699 comm=bash oom_score_adj=-1000
bash-7699  [007] ...1  5151.818022: task_newtask: pid=7729 comm=bash clone_flags=1200011 oom_score_adj=-1000
ls-7729  [003] ...2  5151.818504: task_rename: pid=7729 oldcomm=bash newcomm=ls oom_score_adj=-1000
bash-7699  [002] ...1  5175.701468: task_newtask: pid=7730 comm=bash clone_flags=1200011 oom_score_adj=-1000
grep-7730  [007] ...2  5175.701993: task_rename: pid=7730 oldcomm=bash newcomm=grep oom_score_adj=-1000

Signed-off-by: KAMEZAWA Hiroyuki 
Cc: KOSAKI Motohiro 
Acked-by: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

trim fs/internal.h

2012-01-04T03:52:35+00:00

some stuff in there can actually become static; some belongs to pnode.h
as it's a private interface between namespace.c and pnode.c...

Signed-off-by: Al Viro

oom: remove oom_disable_count

2011-11-01T00:30:45+00:00

This removes mm->oom_disable_count entirely since it's unnecessary and
currently buggy.  The counter was intended to be per-process but it's
currently decremented in the exit path for each thread that exits, causing
it to underflow.

The count was originally intended to prevent oom killing threads that
share memory with threads that cannot be killed since it doesn't lead to
future memory freeing.  The counter could be fixed to represent all
threads sharing the same mm, but it's better to remove the count since:

 - it is possible that the OOM_DISABLE thread sharing memory with the
   victim is waiting on that thread to exit and will actually cause
   future memory freeing, and

 - there is no guarantee that a thread is disabled from oom killing just
   because another thread sharing its mm is oom disabled.

Signed-off-by: David Rientjes 
Reported-by: Oleg Nesterov 
Reviewed-by: Oleg Nesterov 
Cc: Ying Han 
Cc: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

move RLIMIT_NPROC check from set_user() to do_execve_common()

2011-08-11T18:24:42+00:00

The patch http://lkml.org/lkml/2003/7/13/226 introduced an RLIMIT_NPROC
check in set_user() to check for NPROC exceeding via setuid() and
similar functions.

Before the check there was a possibility to greatly exceed the allowed
number of processes by an unprivileged user if the program relied on
rlimit only.  But the check created new security threat: many poorly
written programs simply don't check setuid() return code and believe it
cannot fail if executed with root privileges.  So, the check is removed
in this patch because of too often privilege escalations related to
buggy programs.

The NPROC can still be enforced in the common code flow of daemons
spawning user processes.  Most of daemons do fork()+setuid()+execve().
The check introduced in execve() (1) enforces the same limit as in
setuid() and (2) doesn't create similar security issues.

Neil Brown suggested to track what specific process has exceeded the
limit by setting PF_NPROC_EXCEEDED process flag.  With the change only
this process would fail on execve(), and other processes' execve()
behaviour is not changed.

Solar Designer suggested to re-check whether NPROC limit is still
exceeded at the moment of execve().  If the process was sleeping for
days between set*uid() and execve(), and the NPROC counter step down
under the limit, the defered execve() failure because NPROC limit was
exceeded days ago would be unexpected.  If the limit is not exceeded
anymore, we clear the flag on successful calls to execve() and fork().

The flag is also cleared on successful calls to set_user() as the limit
was exceeded for the previous user, not the current one.

Similar check was introduced in -ow patches (without the process flag).

v3 - clear PF_NPROC_EXCEEDED on successful calls to set_user().

Reviewed-by: James Morris 
Signed-off-by: Vasiliy Kulikov 
Acked-by: NeilBrown 
Signed-off-by: Linus Torvalds

fs/exec.c:acct_arg_size(): ptl is no longer needed for add_mm_counter()

2011-07-26T23:49:44+00:00

acct_arg_size() takes ->page_table_lock around add_mm_counter() if
!SPLIT_RSS_COUNTING.  This is not needed after commit 172703b08cd0 ("mm:
delete non-atomic mm counter implementation").

Signed-off-by: Oleg Nesterov 
Reviewed-by: Matt Fleming 
Cc: Dave Hansen 
Cc: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

exec: do not retry load_binary method if CONFIG_MODULES=n

2011-07-26T23:49:44+00:00

If CONFIG_MODULES=n, it makes no sense to retry the list of binary formats
handler because the list will not be modified by request_module().

Signed-off-by: Tetsuo Handa 
Cc: Richard Weinberger 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds