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  1. 02 3月, 2017 2 次提交
  3. 19 1月, 2017 2 次提交
    • G
      Introduce STATIC_USERMODEHELPER to mediate call_usermodehelper() · 64e90a8a
      由 Greg Kroah-Hartman 提交于 
      Some usermode helper applications are defined at kernel build time, while
others can be changed at runtime.  To provide a sane way to filter these, add a
new kernel option "STATIC_USERMODEHELPER".  This option routes all
call_usermodehelper() calls through this binary, no matter what the caller
wishes to have called.

The new binary (by default set to /sbin/usermode-helper, but can be changed
through the STATIC_USERMODEHELPER_PATH option) can properly filter the
requested programs to be run by the kernel by looking at the first argument
that is passed to it.  All other options should then be passed onto the proper
program if so desired.

To disable all call_usermodehelper() calls by the kernel, set
STATIC_USERMODEHELPER_PATH to an empty string.

Thanks to Neil Brown for the idea of this feature.

Cc: NeilBrown <neilb@suse.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      64e90a8a
    • G
      kmod: make usermodehelper path a const string · 6d2c5d6c
      由 Greg Kroah-Hartman 提交于 
      This is in preparation for making it so that usermode helper programs
can't be changed, if desired, by userspace.  We will tackle the mess of
cleaning up the write-ability of argv and env later, that's going to
take more work, for much less gain...
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      6d2c5d6c
  5. 25 12月, 2016 1 次提交
  7. 23 10月, 2015 1 次提交
  9. 11 9月, 2015 6 次提交
    • F
      kmod: handle UMH_WAIT_PROC from system unbound workqueue · bb304a5c
      由 Frederic Weisbecker 提交于 
      The UMH_WAIT_PROC handler runs in its own thread in order to make sure
that waiting for the exec kernel thread completion won't block other
usermodehelper queued jobs.

On older workqueue implementations, worklets couldn't sleep without
blocking the rest of the queue.  But now the workqueue subsystem handles
that.  Khelper still had the older limitation due to its singlethread
properties but we replaced it to system unbound workqueues.

Those are affine to the current node and can block up to some number of
instances.

They are a good candidate to handle UMH_WAIT_PROC assuming that we have
enough system unbound workers to handle lots of parallel usermodehelper
jobs.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      bb304a5c
    • F
      kmod: use system_unbound_wq instead of khelper · 90f02303
      由 Frederic Weisbecker 提交于 
      We need to launch the usermodehelper kernel threads with the widest
affinity and this is partly why we use khelper.  This workqueue has
unbound properties and thus a wide affinity inherited by all its children.

Now khelper also has special properties that we aren't much interested in:
ordered and singlethread.  There is really no need about ordering as all
we do is creating kernel threads.  This can be done concurrently.  And
singlethread is a useless limitation as well.

The workqueue engine already proposes generic unbound workqueues that
don't share these useless properties and handle well parallel jobs.

The only worrysome specific is their affinity to the node of the current
CPU.  It's fine for creating the usermodehelper kernel threads but those
inherit this affinity for longer jobs such as requesting modules.

This patch proposes to use these node affine unbound workqueues assuming
that a node is sufficient to handle several parallel usermodehelper
requests.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      90f02303
    • F
      kmod: add up-to-date explanations on the purpose of each asynchronous levels · b639e86b
      由 Frederic Weisbecker 提交于 
      There seem to be quite some confusions on the comments, likely due to
changes that came after them.

Now since it's very non obvious why we have 3 levels of asynchronous code
to implement usermodehelpers, it's important to comment in detail the
reason of this layout.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b639e86b
    • F
      kmod: remove unecessary explicit wide CPU affinity setting · d097c024
      由 Frederic Weisbecker 提交于 
      Khelper is affine to all CPUs.  Now since it creates the
call_usermodehelper_exec_[a]sync() kernel threads, those inherit the wide
affinity.

As such explicitly forcing a wide affinity from those kernel threads
is like a no-op.

Just remove it. It's needless and it breaks CPU isolation users who
rely on workqueue affinity tuning.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d097c024
    • F
      kmod: bunch of internal functions renames · b6b50a81
      由 Frederic Weisbecker 提交于 
      This patchset does a bunch of cleanups and converts khelper to use system
unbound workqueues.  The 3 first patches should be uncontroversial.  The
last 2 patches are debatable.

Kmod creates kernel threads that perform userspace jobs and we want those
to have a large affinity in order not to contend busy CPUs.  This is
(partly) why we use khelper which has a wide affinity that the kernel
threads it create can inherit from.  Now khelper is a dedicated workqueue
that has singlethread properties which we aren't interested in.

Hence those two debatable changes:

_ We would like to use generic workqueues. System unbound workqueues are
  a very good candidate but they are not wide affine, only node affine.
  Now probably a node is enough to perform many parallel kmod jobs.

_ We would like to remove the wait_for_helper kernel thread (UMH_WAIT_PROC
  handler) to use the workqueue. It means that if the workqueue blocks,
  and no other worker can take pending kmod request, we can be screwed.
  Now if we have 512 threads, this should be enough.

This patch (of 5):

Underscores on function names aren't much verbose to explain the purpose
of a function.  And kmod has interesting such flavours.

Lets rename the following functions:

* __call_usermodehelper -> call_usermodehelper_exec_work
* ____call_usermodehelper -> call_usermodehelper_exec_async
* wait_for_helper -> call_usermodehelper_exec_sync
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b6b50a81
    • N
      kmod: correct documentation of return status of request_module · 60b61a6f
      由 NeilBrown 提交于 
      If request_module() successfully runs modprobe, but modprobe exits with a
non-zero status, then the return value from request_module() will be that
(positive) error status.  So the return from request_module can be:

 negative errno
 zero for success
 positive exit code.
Signed-off-by: NNeilBrown <neilb@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      60b61a6f
  11. 11 12月, 2014 2 次提交
  13. 30 10月, 2014 1 次提交
    • M
      kernel/kmod: fix use-after-free of the sub_info structure · 0baf2a4d
      由 Martin Schwidefsky 提交于 
      Found this in the message log on a s390 system:

    BUG kmalloc-192 (Not tainted): Poison overwritten
    Disabling lock debugging due to kernel taint
    INFO: 0x00000000684761f4-0x00000000684761f7. First byte 0xff instead of 0x6b
    INFO: Allocated in call_usermodehelper_setup+0x70/0x128 age=71 cpu=2 pid=648
     __slab_alloc.isra.47.constprop.56+0x5f6/0x658
     kmem_cache_alloc_trace+0x106/0x408
     call_usermodehelper_setup+0x70/0x128
     call_usermodehelper+0x62/0x90
     cgroup_release_agent+0x178/0x1c0
     process_one_work+0x36e/0x680
     worker_thread+0x2f0/0x4f8
     kthread+0x10a/0x120
     kernel_thread_starter+0x6/0xc
     kernel_thread_starter+0x0/0xc
    INFO: Freed in call_usermodehelper_exec+0x110/0x1b8 age=71 cpu=2 pid=648
     __slab_free+0x94/0x560
     kfree+0x364/0x3e0
     call_usermodehelper_exec+0x110/0x1b8
     cgroup_release_agent+0x178/0x1c0
     process_one_work+0x36e/0x680
     worker_thread+0x2f0/0x4f8
     kthread+0x10a/0x120
     kernel_thread_starter+0x6/0xc
     kernel_thread_starter+0x0/0xc

There is a use-after-free bug on the subprocess_info structure allocated
by the user mode helper.  In case do_execve() returns with an error
____call_usermodehelper() stores the error code to sub_info->retval, but
sub_info can already have been freed.

Regarding UMH_NO_WAIT, the sub_info structure can be freed by
__call_usermodehelper() before the worker thread returns from
do_execve(), allowing memory corruption when do_execve() failed after
exec_mmap() is called.

Regarding UMH_WAIT_EXEC, the call to umh_complete() allows
call_usermodehelper_exec() to continue which then frees sub_info.

To fix this race the code needs to make sure that the call to
call_usermodehelper_freeinfo() is always done after the last store to
sub_info->retval.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0baf2a4d
  15. 07 6月, 2014 1 次提交
  17. 18 4月, 2014 1 次提交
  19. 06 2月, 2014 1 次提交
    • L
      execve: use 'struct filename *' for executable name passing · c4ad8f98
      由 Linus Torvalds 提交于 
      This changes 'do_execve()' to get the executable name as a 'struct
filename', and to free it when it is done.  This is what the normal
users want, and it simplifies and streamlines their error handling.

The controlled lifetime of the executable name also fixes a
use-after-free problem with the trace_sched_process_exec tracepoint: the
lifetime of the passed-in string for kernel users was not at all
obvious, and the user-mode helper code used UMH_WAIT_EXEC to serialize
the pathname allocation lifetime with the execve() having finished,
which in turn meant that the trace point that happened after
mm_release() of the old process VM ended up using already free'd memory.

To solve the kernel string lifetime issue, this simply introduces
"getname_kernel()" that works like the normal user-space getname()
function, except with the source coming from kernel memory.

As Oleg points out, this also means that we could drop the tcomm[] array
from 'struct linux_binprm', since the pathname lifetime now covers
setup_new_exec().  That would be a separate cleanup.
Reported-by: NIgor Zhbanov <i.zhbanov@samsung.com>
Tested-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c4ad8f98
  21. 01 10月, 2013 1 次提交
  23. 04 7月, 2013 1 次提交
  25. 17 5月, 2013 1 次提交
  27. 01 5月, 2013 3 次提交
  29. 23 1月, 2013 1 次提交
    • T
      async, kmod: warn on synchronous request_module() from async workers · 0fdff3ec
      由 Tejun Heo 提交于 
      Synchronous requet_module() from an async worker can lead to deadlock
because module init path may invoke async_synchronize_full().  The
async worker waits for request_module() to complete and the module
loading waits for the async task to finish.  This bug happened in the
block layer because of default elevator auto-loading.

Block layer has been updated not to do default elevator auto-loading
and it has been decided to disallow synchronous request_module() from
async workers.

Trigger WARN_ON_ONCE() on synchronous request_module() from async
workers.

For more details, please refer to the following thread.

  http://thread.gmane.org/gmane.linux.kernel/1420814Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NAlex Riesen <raa.lkml@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
      0fdff3ec
  31. 20 12月, 2012 1 次提交
  33. 13 10月, 2012 1 次提交
    • A
      infrastructure for saner ret_from_kernel_thread semantics · a74fb73c
      由 Al Viro 提交于 
      * allow kernel_execve() leave the actual return to userland to
caller (selected by CONFIG_GENERIC_KERNEL_EXECVE).  Callers
updated accordingly.
* architecture that does select GENERIC_KERNEL_EXECVE in its
Kconfig should have its ret_from_kernel_thread() do this:
	call schedule_tail
	call the callback left for it by copy_thread(); if it ever
returns, that's because it has just done successful kernel_execve()
	jump to return from syscall
IOW, its only difference from ret_from_fork() is that it does call the
callback.
* such an architecture should also get rid of ret_from_kernel_execve()
and __ARCH_WANT_KERNEL_EXECVE

This is the last part of infrastructure patches in that area - from
that point on work on different architectures can live independently.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      a74fb73c
  35. 12 10月, 2012 1 次提交
    • A
      make sure that kernel_thread() callbacks call do_exit() themselves · fb45550d
      由 Al Viro 提交于 
      Most of them never returned anyway - only two functions had to be
changed.  That allows to simplify their callers a whole lot.

Note that this does *not* apply to kthread_run() callbacks - all of
those had been called from the same kernel_thread() callback, which
did do_exit() already.  This is strictly about very few low-level
kernel_thread() callbacks (there are only 6 of those, mostly as part
of kthread.h and kmod.h exported mechanisms, plus kernel_init()
itself).
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      fb45550d
  37. 31 7月, 2012 2 次提交
    • T
      kmod: avoid deadlock from recursive kmod call · 0f20784d
      由 Tetsuo Handa 提交于 
      The system deadlocks (at least since 2.6.10) when
call_usermodehelper(UMH_WAIT_EXEC) request triggers
call_usermodehelper(UMH_WAIT_PROC) request.

This is because "khelper thread is waiting for the worker thread at
wait_for_completion() in do_fork() since the worker thread was created
with CLONE_VFORK flag" and "the worker thread cannot call complete()
because do_execve() is blocked at UMH_WAIT_PROC request" and "the khelper
thread cannot start processing UMH_WAIT_PROC request because the khelper
thread is waiting for the worker thread at wait_for_completion() in
do_fork()".

The easiest example to observe this deadlock is to use a corrupted
/sbin/hotplug binary (like shown below).

  # : > /tmp/dummy
  # chmod 755 /tmp/dummy
  # echo /tmp/dummy > /proc/sys/kernel/hotplug
  # modprobe whatever

call_usermodehelper("/tmp/dummy", UMH_WAIT_EXEC) is called from
kobject_uevent_env() in lib/kobject_uevent.c upon loading/unloading a
module.  do_execve("/tmp/dummy") triggers a call to
request_module("binfmt-0000") from search_binary_handler() which in turn
calls call_usermodehelper(UMH_WAIT_PROC).

In order to avoid deadlock, as a for-now and easy-to-backport solution, do
not try to call wait_for_completion() in call_usermodehelper_exec() if the
worker thread was created by khelper thread with CLONE_VFORK flag.  Future
and fundamental solution might be replacing singleton khelper thread with
some workqueue so that recursive calls up to max_active dependency loop
can be handled without deadlock.

[akpm@linux-foundation.org: add comment to kmod_thread_locker]
Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0f20784d
    • A
      kernel/kmod.c: document call_usermodehelper_fns() a bit · 79c743dd
      由 Andrew Morton 提交于 
      This function's interface is, uh, subtle.  Attempt to apologise for it.

Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      79c743dd
  39. 01 6月, 2012 3 次提交
  41. 29 3月, 2012 3 次提交
    • R
      PM / Sleep: Mitigate race between the freezer and request_firmware() · 247bc037
      由 Rafael J. Wysocki 提交于 
      There is a race condition between the freezer and request_firmware()
such that if request_firmware() is run on one CPU and
freeze_processes() is run on another CPU and usermodehelper_disable()
called by it succeeds to grab umhelper_sem for writing before
usermodehelper_read_trylock() called from request_firmware()
acquires it for reading, the request_firmware() will fail and
trigger a WARN_ON() complaining that it was called at a wrong time.
However, in fact, it wasn't called at a wrong time and
freeze_processes() simply happened to be executed simultaneously.

To avoid this race, at least in some cases, modify
usermodehelper_read_trylock() so that it doesn't fail if the
freezing of tasks has just started and hasn't been completed yet.
Instead, during the freezing of tasks, it will try to freeze the
task that has called it so that it can wait until user space is
thawed without triggering the scary warning.

For this purpose, change usermodehelper_disabled so that it can
take three different values, UMH_ENABLED (0), UMH_FREEZING and
UMH_DISABLED.  The first one means that usermode helpers are
enabled, the last one means "hard disable" (i.e. the system is not
ready for usermode helpers to be used) and the second one
is reserved for the freezer.  Namely, when freeze_processes() is
started, it sets usermodehelper_disabled to UMH_FREEZING which
tells usermodehelper_read_trylock() that it shouldn't fail just
yet and should call try_to_freeze() if woken up and cannot
return immediately.  This way all freezable tasks that happen
to call request_firmware() right before freeze_processes() is
started and lose the race for umhelper_sem with it will be
frozen and will sleep until thaw_processes() unsets
usermodehelper_disabled.  [For the non-freezable callers of
request_firmware() the race for umhelper_sem against
freeze_processes() is unfortunately unavoidable.]
Reported-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
      247bc037
    • R
      firmware_class: Do not warn that system is not ready from async loads · 9b78c1da
      由 Rafael J. Wysocki 提交于 
      If firmware is requested asynchronously, by calling
request_firmware_nowait(), there is no reason to fail the request
(and warn the user) when the system is (presumably temporarily)
unready to handle it (because user space is not available yet or
frozen).  For this reason, introduce an alternative routine for
read-locking umhelper_sem, usermodehelper_read_lock_wait(), that
will wait for usermodehelper_disabled to be unset (possibly with
a timeout) and make request_firmware_work_func() use it instead of
usermodehelper_read_trylock().

Accordingly, modify request_firmware() so that it uses
usermodehelper_read_trylock() to acquire umhelper_sem and remove
the code related to that lock from _request_firmware().
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
      9b78c1da
    • R
      firmware_class: Rework usermodehelper check · fe2e39d8
      由 Rafael J. Wysocki 提交于 
      Instead of two functions, read_lock_usermodehelper() and
usermodehelper_is_disabled(), used in combination, introduce
usermodehelper_read_trylock() that will only return with umhelper_sem
held if usermodehelper_disabled is unset (and will return -EAGAIN
otherwise) and make _request_firmware() use it.

Rename read_unlock_usermodehelper() to
usermodehelper_read_unlock() to follow the naming convention of the
new function.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
      fe2e39d8
  43. 24 3月, 2012 4 次提交