linux.git/kernel/livepatch/transition.c, branch v6.6.132

livepatch: Make 'klp_stack_entries' static

2023-06-05T11:56:52+00:00

The 'klp_stack_entries' percpu array is only used in transition.c.  Make
it static.

Fixes: e92606fa172f ("livepatch: Convert stack entries array to percpu")
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202305171329.i0UQ4TJa-lkp@intel.com/
Signed-off-by: Josh Poimboeuf 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/5115752fca6537720700f4bf5b178959dfbca41a.1685488550.git.jpoimboe@kernel.org

livepatch,sched: Add livepatch task switching to cond_resched()

2023-03-22T16:09:28+00:00

There have been reports [1][2] of live patches failing to complete
within a reasonable amount of time due to CPU-bound kthreads.

Fix it by patching tasks in cond_resched().

There are four different flavors of cond_resched(), depending on the
kernel configuration.  Hook into all of them.

A more elegant solution might be to use a preempt notifier.  However,
non-ORC unwinders can't unwind a preempted task reliably.

[1] https://lore.kernel.org/lkml/20220507174628.2086373-1-song@kernel.org/
[2] https://lkml.kernel.org/lkml/20230120-vhost-klp-switching-v1-0-7c2b65519c43@kernel.org

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Petr Mladek 
Tested-by: Seth Forshee (DigitalOcean) 
Link: https://lore.kernel.org/r/4ae981466b7814ec221014fc2554b2f86f3fb70b.1677257135.git.jpoimboe@kernel.org

livepatch: Skip task_call_func() for current task

2023-03-22T16:09:28+00:00

The current task doesn't need the scheduler's protection to unwind its
own stack.

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Petr Mladek 
Tested-by: Seth Forshee (DigitalOcean) 
Link: https://lore.kernel.org/r/4b92e793462d532a05f03767151fa29db3e68e13.1677257135.git.jpoimboe@kernel.org

livepatch: Convert stack entries array to percpu

2023-03-22T16:09:28+00:00

The entries array in klp_check_stack() is static local because it's too
big to be reasonably allocated on the stack.  Serialized access is
enforced by the klp_mutex.

In preparation for calling klp_check_stack() without the mutex (from
cond_resched), convert it to a percpu variable.

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20230313233346.kayh4t2lpicjkpsv@treble

livepatch: Move the result-invariant calculation out of the loop

2022-10-18T13:50:31+00:00

The calculation results of the variables 'func_addr' and 'func_size' are
not affected by the for loop and do not change due to the changes of
entries[i]. The performance can be improved by moving it outside the loop.

No functional change.

Signed-off-by: Zhen Lei 
Reviewed-by: Petr Mladek 
Signed-off-by: Jiri Kosina

livepatch: fix race between fork and KLP transition

2022-09-01T12:53:18+00:00

The KLP transition code depends on the TIF_PATCH_PENDING and
the task->patch_state to stay in sync. On a normal (forward)
transition, TIF_PATCH_PENDING will be set on every task in
the system, while on a reverse transition (after a failed
forward one) first TIF_PATCH_PENDING will be cleared from
every task, followed by it being set on tasks that need to
be transitioned back to the original code.

However, the fork code copies over the TIF_PATCH_PENDING flag
from the parent to the child early on, in dup_task_struct and
setup_thread_stack. Much later, klp_copy_process will set
child->patch_state to match that of the parent.

However, the parent's patch_state may have been changed by KLP loading
or unloading since it was initially copied over into the child.

This results in the KLP code occasionally hitting this warning in
klp_complete_transition:

        for_each_process_thread(g, task) {
                WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING));
                task->patch_state = KLP_UNDEFINED;
        }

Set, or clear, the TIF_PATCH_PENDING flag in the child task
depending on whether or not it is needed at the time
klp_copy_process is called, at a point in copy_process where the
tasklist_lock is held exclusively, preventing races with the KLP
code.

The KLP code does have a few places where the state is changed
without the tasklist_lock held, but those should not cause
problems because klp_update_patch_state(current) cannot be
called while the current task is in the middle of fork,
klp_check_and_switch_task() which is called under the pi_lock,
which prevents rescheduling, and manipulation of the patch
state of idle tasks, which do not fork.

This should prevent this warning from triggering again in the
future, and close the race for both normal and reverse transitions.

Signed-off-by: Rik van Riel 
Reported-by: Breno Leitao 
Reviewed-by: Petr Mladek 
Acked-by: Josh Poimboeuf 
Fixes: d83a7cb375ee ("livepatch: change to a per-task consistency model")
Cc: stable@kernel.org
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20220808150019.03d6a67b@imladris.surriel.com

Merge tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-03-29T00:29:53+00:00

Pull ptrace cleanups from Eric Biederman:
 "This set of changes removes tracehook.h, moves modification of all of
  the ptrace fields inside of siglock to remove races, adds a missing
  permission check to ptrace.c

  The removal of tracehook.h is quite significant as it has been a major
  source of confusion in recent years. Much of that confusion was around
  task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the
  semantics clearer).

  For people who don't know tracehook.h is a vestiage of an attempt to
  implement uprobes like functionality that was never fully merged, and
  was later superseeded by uprobes when uprobes was merged. For many
  years now we have been removing what tracehook functionaly a little
  bit at a time. To the point where anything left in tracehook.h was
  some weird strange thing that was difficult to understand"

* tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  ptrace: Remove duplicated include in ptrace.c
  ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
  ptrace: Return the signal to continue with from ptrace_stop
  ptrace: Move setting/clearing ptrace_message into ptrace_stop
  tracehook: Remove tracehook.h
  resume_user_mode: Move to resume_user_mode.h
  resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
  signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
  task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
  task_work: Call tracehook_notify_signal from get_signal on all architectures
  task_work: Introduce task_work_pending
  task_work: Remove unnecessary include from posix_timers.h
  ptrace: Remove tracehook_signal_handler
  ptrace: Remove arch_syscall_{enter,exit}_tracehook
  ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
  ptrace/arm: Rename tracehook_report_syscall report_syscall
  ptrace: Move ptrace_report_syscall into ptrace.h

livepatch: Don't block removal of patches that are safe to unload

2022-03-17T18:02:30+00:00

module_put() is not called for a patch with "forced" flag. It should
block the removal of the livepatch module when the code might still
be in use after forced transition.

klp_force_transition() currently sets "forced" flag for all patches on
the list.

In fact, any patch can be safely unloaded when it passed through
the consistency model in KLP_UNPATCHED transition.

In other words, the "forced" flag must be set only for livepatches
that are being removed. In particular, set the "forced" flag:

  + only for klp_transition_patch when the transition to KLP_UNPATCHED
    state was forced.

  + all replaced patches when the transition to KLP_PATCHED state was
    forced and the patch was replacing the existing patches.

Signed-off-by: Chengming Zhou 
Acked-by: Joe Lawrence 
Reviewed-by: Petr Mladek 
Tested-by: Petr Mladek 
[mbenes@suse.cz: wording improvements]
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20220312152220.88127-1-zhouchengming@bytedance.com

tracehook: Remove tracehook.h

2022-03-10T22:51:51+00:00

Now that all of the definitions have moved out of tracehook.h into
ptrace.h, sched/signal.h, resume_user_mode.h there is nothing left in
tracehook.h so remove it.

Update the few files that were depending upon tracehook.h to bring in
definitions to use the headers they need directly.

Reviewed-by: Kees Cook 
Link: https://lkml.kernel.org/r/20220309162454.123006-13-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman"

sched,livepatch: Use wake_up_if_idle()

2021-10-14T11:09:25+00:00

Make sure to prod idle CPUs so they call klp_update_patch_state().

Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Petr Mladek 
Acked-by: Miroslav Benes 
Acked-by: Vasily Gorbik 
Tested-by: Petr Mladek 
Tested-by: Vasily Gorbik  # on s390
Link: https://lkml.kernel.org/r/20210929151723.162004989@infradead.org