linux.git/kernel/fork.c, branch v4.11.5

kthread: Fix use-after-free if kthread fork fails

2017-06-14T13:07:38+00:00

commit 4d6501dce079c1eb6bf0b1d8f528a5e81770109e upstream.

If a kthread forks (e.g. usermodehelper since commit 1da5c46fa965) but
fails in copy_process() between calling dup_task_struct() and setting
p->set_child_tid, then the value of p->set_child_tid will be inherited
from the parent and get prematurely freed by free_kthread_struct().

    kthread()
     - worker_thread()
        - process_one_work()
        |  - call_usermodehelper_exec_work()
        |     - kernel_thread()
        |        - _do_fork()
        |           - copy_process()
        |              - dup_task_struct()
        |                 - arch_dup_task_struct()
        |                    - tsk->set_child_tid = current->set_child_tid // implied
        |              - ...
        |              - goto bad_fork_*
        |              - ...
        |              - free_task(tsk)
        |                 - free_kthread_struct(tsk)
        |                    - kfree(tsk->set_child_tid)
        - ...
        - schedule()
           - __schedule()
              - wq_worker_sleeping()
                 - kthread_data(task)->flags // UAF

The problem started showing up with commit 1da5c46fa965 since it reused
->set_child_tid for the kthread worker data.

A better long-term solution might be to get rid of the ->set_child_tid
abuse. The comment in set_kthread_struct() also looks slightly wrong.

Debugged-by: Jamie Iles 
Fixes: 1da5c46fa965 ("kthread: Make struct kthread kmalloc'ed")
Signed-off-by: Vegard Nossum 
Acked-by: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Greg Kroah-Hartman 
Cc: Andy Lutomirski 
Cc: Frederic Weisbecker 
Cc: Jamie Iles 
Link: http://lkml.kernel.org/r/20170509073959.17858-1-vegard.nossum@oracle.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

stackprotector: Increase the per-task stack canary's random range from 32 bits to 64 bits on 64-bit platforms

2017-05-25T13:46:26+00:00

commit 5ea30e4e58040cfd6434c2f33dc3ea76e2c15b05 upstream.

The stack canary is an 'unsigned long' and should be fully initialized to
random data rather than only 32 bits of random data.

Signed-off-by: Daniel Micay 
Acked-by: Arjan van de Ven 
Acked-by: Rik van Riel 
Acked-by: Kees Cook 
Cc: Arjan van Ven 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: kernel-hardening@lists.openwall.com
Link: http://lkml.kernel.org/r/20170504133209.3053-1-danielmicay@gmail.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

pid_ns: Fix race between setns'ed fork() and zap_pid_ns_processes()

2017-05-25T13:46:17+00:00

commit 3fd37226216620c1a468afa999739d5016fbc349 upstream.

Imagine we have a pid namespace and a task from its parent's pid_ns,
which made setns() to the pid namespace. The task is doing fork(),
while the pid namespace's child reaper is dying. We have the race
between them:

Task from parent pid_ns             Child reaper
copy_process()                      ..
  alloc_pid()                       ..
  ..                                zap_pid_ns_processes()
  ..                                  disable_pid_allocation()
  ..                                  read_lock(&tasklist_lock)
  ..                                  iterate over pids in pid_ns
  ..                                    kill tasks linked to pids
  ..                                  read_unlock(&tasklist_lock)
  write_lock_irq(&tasklist_lock);   ..
  attach_pid(p, PIDTYPE_PID);       ..
  ..                                ..

So, just created task p won't receive SIGKILL signal,
and the pid namespace will be in contradictory state.
Only manual kill will help there, but does the userspace
care about this? I suppose, the most users just inject
a task into a pid namespace and wait a SIGCHLD from it.

The patch fixes the problem. It simply checks for
(pid_ns->nr_hashed & PIDNS_HASH_ADDING) in copy_process().
We do it under the tasklist_lock, and can't skip
PIDNS_HASH_ADDING as noted by Oleg:

"zap_pid_ns_processes() does disable_pid_allocation()
and then takes tasklist_lock to kill the whole namespace.
Given that copy_process() checks PIDNS_HASH_ADDING
under write_lock(tasklist) they can't race;
if copy_process() takes this lock first, the new child will
be killed, otherwise copy_process() can't miss
the change in ->nr_hashed."

If allocation is disabled, we just return -ENOMEM
like it's made for such cases in alloc_pid().

v2: Do not move disable_pid_allocation(), do not
introduce a new variable in copy_process() and simplify
the patch as suggested by Oleg Nesterov.
Account the problem with double irq enabling
found by Eric W. Biederman.

Fixes: c876ad768215 ("pidns: Stop pid allocation when init dies")
Signed-off-by: Kirill Tkhai 
CC: Andrew Morton 
CC: Ingo Molnar 
CC: Peter Zijlstra 
CC: Oleg Nesterov 
CC: Mike Rapoport 
CC: Michal Hocko 
CC: Andy Lutomirski 
CC: "Eric W. Biederman" 
CC: Andrei Vagin 
CC: Cyrill Gorcunov 
CC: Serge Hallyn 
Acked-by: Oleg Nesterov 
Signed-off-by: Eric W. Biederman 
Signed-off-by: Greg Kroah-Hartman

sched/headers, RCU: Move rcu_copy_process() from to kernel/fork.c

2017-03-03T00:43:46+00:00

Move rcu_copy_process() into kernel/fork.c, which is the only
user of this inline function.

This simplifies  to the level that 
does not have to be included in it anymore - which change is done
in a subsequent patch.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/headers: Prepare to move cputime functionality from into

2017-03-02T07:42:39+00:00

Introduce a trivial, mostly empty  header
to prepare for the moving of cputime functionality out of sched.h.

Update all code that relies on these facilities.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:36+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:35+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:34+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/headers: Prepare for the removal of from

2017-03-02T07:42:32+00:00

Fix up missing #includes in other places that rely on sched.h doing that for them.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:30+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar