linux.git/kernel/fork.c, branch v3.18.128

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

2018-09-26T06:33:53+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 
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170509073959.17858-1-vegard.nossum@oracle.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Amit Pundir 
Signed-off-by: Greg Kroah-Hartman

fork: don't copy inconsistent signal handler state to child

2018-09-26T06:33:50+00:00

[ Upstream commit 06e62a46bbba20aa5286102016a04214bb446141 ]

Before this change, if a multithreaded process forks while one of its
threads is changing a signal handler using sigaction(), the memcpy() in
copy_sighand() can race with the struct assignment in do_sigaction().  It
isn't clear whether this can cause corruption of the userspace signal
handler pointer, but it definitely can cause inconsistency between
different fields of struct sigaction.

Take the appropriate spinlock to avoid this.

I have tested that this patch prevents inconsistency between sa_sigaction
and sa_flags, which is possible before this patch.

Link: http://lkml.kernel.org/r/20180702145108.73189-1-jannh@google.com
Signed-off-by: Jann Horn 
Acked-by: Michal Hocko 
Reviewed-by: Andrew Morton 
Cc: Rik van Riel 
Cc: "Peter Zijlstra (Intel)" 
Cc: Kees Cook 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin 
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

2017-06-14T10:54:19+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
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170504133209.3053-1-danielmicay@gmail.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

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

2017-06-07T10:01:50+00:00

This reverts commit 609a3e81550b0b4ea87197b0f59455a7bcff975a which is
commit 5ea30e4e58040cfd6434c2f33dc3ea76e2c15b05 upstream.

It shouldn't have been backported to 3.18, as we do not have
get_random_long() in that kernel tree.

Reported-by: Philip Müller 
Cc: Daniel Micay 
Cc: Arjan van de Ven 
Cc: Rik van Riel 
Cc: Kees Cook 
Cc: Arjan van Ven 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: kernel-hardening@lists.openwall.com
Cc: Ingo Molnar 
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

2017-05-25T12:18:01+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

unshare: Unsharing a thread does not require unsharing a vm

2015-10-07T14:03:47+00:00

[ Upstream commit 12c641ab8270f787dfcce08b5f20ce8b65008096 ]

In the logic in the initial commit of unshare made creating a new
thread group for a process, contingent upon creating a new memory
address space for that process.  That is wrong.  Two separate
processes in different thread groups can share a memory address space
and clone allows creation of such proceses.

This is significant because it was observed that mm_users > 1 does not
mean that a process is multi-threaded, as reading /proc/PID/maps
temporarily increments mm_users, which allows other processes to
(accidentally) interfere with unshare() calls.

Correct the check in check_unshare_flags() to test for
!thread_group_empty() for CLONE_THREAD, CLONE_SIGHAND, and CLONE_VM.
For sighand->count > 1 for CLONE_SIGHAND and CLONE_VM.
For !current_is_single_threaded instead of mm_users > 1 for CLONE_VM.

By using the correct checks in unshare this removes the possibility of
an accidental denial of service attack.

Additionally using the correct checks in unshare ensures that only an
explicit unshare(CLONE_VM) can possibly trigger the slow path of
current_is_single_threaded().  As an explict unshare(CLONE_VM) is
pointless it is not expected there are many applications that make
that call.

Cc: stable@vger.kernel.org
Fixes: b2e0d98705e60e45bbb3c0032c48824ad7ae0704 userns: Implement unshare of the user namespace
Reported-by: Ricky Zhou 
Reported-by: Kees Cook 
Reviewed-by: Kees Cook 
Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Sasha Levin

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

2014-10-13T14:23:15+00:00

Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle were:

   - Optimized support for Intel "Cluster-on-Die" (CoD) topologies (Dave
     Hansen)

   - Various sched/idle refinements for better idle handling (Nicolas
     Pitre, Daniel Lezcano, Chuansheng Liu, Vincent Guittot)

   - sched/numa updates and optimizations (Rik van Riel)

   - sysbench speedup (Vincent Guittot)

   - capacity calculation cleanups/refactoring (Vincent Guittot)

   - Various cleanups to thread group iteration (Oleg Nesterov)

   - Double-rq-lock removal optimization and various refactorings
     (Kirill Tkhai)

   - various sched/deadline fixes

  ... and lots of other changes"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (72 commits)
  sched/dl: Use dl_bw_of() under rcu_read_lock_sched()
  sched/fair: Delete resched_cpu() from idle_balance()
  sched, time: Fix build error with 64 bit cputime_t on 32 bit systems
  sched: Improve sysbench performance by fixing spurious active migration
  sched/x86: Fix up typo in topology detection
  x86, sched: Add new topology for multi-NUMA-node CPUs
  sched/rt: Use resched_curr() in task_tick_rt()
  sched: Use rq->rd in sched_setaffinity() under RCU read lock
  sched: cleanup: Rename 'out_unlock' to 'out_free_new_mask'
  sched: Use dl_bw_of() under RCU read lock
  sched/fair: Remove duplicate code from can_migrate_task()
  sched, mips, ia64: Remove __ARCH_WANT_UNLOCKED_CTXSW
  sched: print_rq(): Don't use tasklist_lock
  sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock()
  sched: Fix the task-group check in tg_has_rt_tasks()
  sched/fair: Leverage the idle state info when choosing the "idlest" cpu
  sched: Let the scheduler see CPU idle states
  sched/deadline: Fix inter- exclusive cpusets migrations
  sched/deadline: Clear dl_entity params when setscheduling to different class
  sched/numa: Kill the wrong/dead TASK_DEAD check in task_numa_fault()
  ...

mm: use VM_BUG_ON_MM where possible

2014-10-10T02:25:58+00:00

Dump the contents of the relevant struct_mm when we hit the bug condition.

Signed-off-by: Sasha Levin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

perf: fix perf bug in fork()

2014-10-02T23:28:44+00:00

Oleg noticed that a cleanup by Sylvain actually uncovered a bug; by
calling perf_event_free_task() when failing sched_fork() we will not yet
have done the memset() on ->perf_event_ctxp[] and will therefore try and
'free' the inherited contexts, which are still in use by the parent
process.  This is bad..

Suggested-by: Oleg Nesterov 
Reported-by: Oleg Nesterov 
Reported-by: Sylvain 'ythier' Hitier 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Ingo Molnar 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

init/main.c: Give init_task a canary

2014-09-19T10:35:22+00:00

Tasks get their end of stack set to STACK_END_MAGIC with the
aim to catch stack overruns. Currently this feature does not
apply to init_task. This patch removes this restriction.

Note that a similar patch was posted by Prarit Bhargava
some time ago but was never merged:

  http://marc.info/?l=linux-kernel&m=127144305403241&w=2

Signed-off-by: Aaron Tomlin 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Oleg Nesterov 
Acked-by: Michael Ellerman 
Cc: aneesh.kumar@linux.vnet.ibm.com
Cc: dzickus@redhat.com
Cc: bmr@redhat.com
Cc: jcastillo@redhat.com
Cc: jgh@redhat.com
Cc: minchan@kernel.org
Cc: tglx@linutronix.de
Cc: hannes@cmpxchg.org
Cc: Alex Thorlton 
Cc: Andrew Morton 
Cc: Benjamin Herrenschmidt 
Cc: Daeseok Youn 
Cc: David Rientjes 
Cc: Fabian Frederick 
Cc: Geert Uytterhoeven 
Cc: Jiri Olsa 
Cc: Kees Cook 
Cc: Kirill A. Shutemov 
Cc: Linus Torvalds 
Cc: Masami Hiramatsu 
Cc: Michael Opdenacker 
Cc: Paul Mackerras 
Cc: Prarit Bhargava 
Cc: Rik van Riel 
Cc: Rusty Russell 
Cc: Seiji Aguchi 
Cc: Steven Rostedt 
Cc: Vladimir Davydov 
Cc: Yasuaki Ishimatsu 
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1410527779-8133-2-git-send-email-atomlin@redhat.com
Signed-off-by: Ingo Molnar