+ mm-fix-kthread_use_mm-vs-tlb-invalidate.patch added to -mm tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



The patch titled
     Subject: mm: fix kthread_use_mm() vs TLB invalidate
has been added to the -mm tree.  Its filename is
     mm-fix-kthread_use_mm-vs-tlb-invalidate.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-fix-kthread_use_mm-vs-tlb-invalidate.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-kthread_use_mm-vs-tlb-invalidate.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Subject: mm: fix kthread_use_mm() vs TLB invalidate

For SMP systems using IPI based TLB invalidation, looking at
current->active_mm is entirely reasonable.  This then presents the
following race condition:

  CPU0			CPU1

  flush_tlb_mm(mm)	use_mm(mm)
    <send-IPI>
			  tsk->active_mm = mm;
			  <IPI>
			    if (tsk->active_mm == mm)
			      // flush TLBs
			  </IPI>
			  switch_mm(old_mm,mm,tsk);

Where it is possible the IPI flushed the TLBs for @old_mm, not @mm,
because the IPI lands before we actually switched.

Avoid this by disabling IRQs across changing ->active_mm and switch_mm().

[ There are all sorts of reasons this might be harmless for various
architecture specific reasons, but best not leave the door open at all.  ]

Link: http://lkml.kernel.org/r/20200721154106.GE10769@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reported-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 kernel/kthread.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/kernel/kthread.c~mm-fix-kthread_use_mm-vs-tlb-invalidate
+++ a/kernel/kthread.c
@@ -1239,13 +1239,15 @@ void kthread_use_mm(struct mm_struct *mm
 	WARN_ON_ONCE(tsk->mm);
 
 	task_lock(tsk);
+	local_irq_disable();
 	active_mm = tsk->active_mm;
 	if (active_mm != mm) {
 		mmgrab(mm);
 		tsk->active_mm = mm;
 	}
 	tsk->mm = mm;
-	switch_mm(active_mm, mm, tsk);
+	switch_mm_irqs_off(active_mm, mm, tsk);
+	local_irq_enable();
 	task_unlock(tsk);
 #ifdef finish_arch_post_lock_switch
 	finish_arch_post_lock_switch();
@@ -1274,9 +1276,11 @@ void kthread_unuse_mm(struct mm_struct *
 
 	task_lock(tsk);
 	sync_mm_rss(mm);
+	local_irq_disable();
 	tsk->mm = NULL;
 	/* active_mm is still 'mm' */
 	enter_lazy_tlb(mm, tsk);
+	local_irq_enable();
 	task_unlock(tsk);
 }
 EXPORT_SYMBOL_GPL(kthread_unuse_mm);
_

Patches currently in -mm which might be from peterz@xxxxxxxxxxxxx are

mm-fix-kthread_use_mm-vs-tlb-invalidate.patch




[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux